chile earthquake case study primary and secondary effects

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Introduction

Earthquake and tsunami

Reconstruction
Legal consequences

Why is an earthquake dangerous?
What are earthquake waves?
How is earthquake magnitude measured?
Where do earthquakes occur?

earthquake. Heavily damaged school in the town of Yingxiu after a major earthquake struck China's Sichuan Province on May 12, 2008.

Chile earthquake of 2010

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LiveScience - Chile Quake and Tsunami Dramatically Altered Ecosystems
Earthquake Engineering Research Institute - The Mw 8.8 Chile Earthquake of February 27, 2010
Table Of Contents

Chile earthquake of 2010 , severe earthquake that occurred on February 27, 2010, off the coast of south-central Chile , causing widespread damage on land and initiating a tsunami that devastated some coastal areas of the country. Together, the earthquake and tsunami were responsible for more than 500 deaths.

chile earthquake case study primary and secondary effects

The magnitude-8.8 earthquake struck at 3:34 am . The epicentre was located some 200 miles (325 km) southwest of the Chilean capital of Santiago , and the focus occurred at a depth of about 22 miles (35 km) below the surface of the Pacific Ocean . The earthquake—resulting from the rupture of a 300- to 375-mile (500- to 600-km) stretch of the fault that separates the South American Plate from the subducting Nazca Plate—was felt as far away as São Paolo , Brazil , and Buenos Aires , Argentina . A 2014 study contended that water pressure built up between the two plates had been the catalyst . The initial event was succeeded in the following weeks by hundreds of aftershocks, many of them of magnitude 5.0 or greater. The temblor was the strongest to strike the region since the magnitude-9.5 event of 1960, considered to be the most powerful earthquake ever recorded. ( See Chile earthquake of 1960 .)

Because the region’s violent tectonic history had made it a focus of seismological study and monitoring, extant GPS sensors installed in Chile and neighbouring countries allowed the detection of subtle shifts in the location of cities, including Concepción and even Buenos Aires , as a result of the quake. A NASA computer model ascertained that the powerful force of the subducting plate had shifted Earth ’s axis sufficiently to shorten the day by more than a microsecond. A study of the aftershocks released in 2014 indicated that two anomalously dense rock structures beneath the South American Plate, previously undetected, had likely slowed the rupture and, as a result, intensified shaking at the surface.

Stress brought on by the convergence of the two tectonic plates caused rocks to shatter along the boundary between them. This forced a portion of the seabed upward, displacing the water above and triggering a tsunami . The Chilean town of Constitución was inundated by waves as high as 50 feet (15 metres), and the port of Talcahuano was damaged by a wave measuring nearly 8 feet (2.4 metres) high. Traveling across the Pacific Ocean at nearly 450 miles (725 km) per hour, the tsunami encountered the Juan Fernández Islands , located approximately 420 miles (675 km) off the coast of Chile. Although observers on the largest of the Juan Fernández Islands reported waves as high as 10 feet (3 metres), the tsunami weakened significantly before it reached the coasts of California , Hawaii , New Zealand , and Japan over the next several hours.

Warm water fuels Hurricane Katrina. This image depicts a 3-day average of actual dea surface temperatures for the Caribbean Sea and Atlantic Ocean, from August 25-27, 2005.

A study published in August 2014 noted that the temblor triggered small earthquakes in Antarctica . It was the first direct evidence that earthquakes could trigger secondary seismic events in the Antarctic’s ice sheets.

Though damage to structures within the zone of the earthquake was likely limited by stringent building codes instituted in the wake of the 1960 earthquake and revised several times during the 1990s, many buildings still sustained significant damage, including nearly 400,000 homes. Particularly affected were Maule and Biobío , two first-order administrative districts along Chile’s southern coast. Large areas of Biobío were left without major services, including water, electricity, and gas, and the tall buildings of Concepción —the capital of the district and one of Chile’s largest cities—were among those most severely damaged. Copper production—a major contributor to Chile’s economy—was halted at several mines, though it resumed after limited power was restored the day after the quake. The weakened state of the electrical grid became apparent when large swathes of the country—including Santiago , which had already endured a week without power following the catastrophe—were faced with a daylong blackout in mid-March after a major transformer failed.

Chilean government officials estimated that two million people had been directly affected by the quake. The Chilean National Emergency Office—initially responsible for documenting the casualties—estimated that more than 800 had died. However, as the Interior Ministry reviewed the data in the following weeks, the official total fluctuated significantly as missing persons were located and computational errors were discovered, leading to a reduction of the death toll by hundreds. Official tallies ultimately attributed more than 500 deaths to the disaster; 150 of those casualties were caused by the tsunami. Most fatalities occurred in the Maule district, with further deaths occurring in Biobío and in coastal and island areas damaged by the tsunami. In Concepción the limited availability of food and gasoline led to widespread looting—a phenomenon that later expanded to nonessential items such as televisions—and the consequent arrest of several dozen people. Chilean Pres. Michelle Bachelet arranged for food retailers to distribute necessities free of charge by the next day, but sporadic theft continued into the week as assistance proved slow to arrive. Isolated areas were particularly vulnerable to looting as the need for supplies became increasingly acute .

Earthquake Case Study: Chile 2010

Chile earthquake 2010.

A shallow focused earthquake of magnitude 8.8 affected Chile in February 2010. Chile is a middle-income country.

What happened in the earthquake?

E.g. foreign aid wasn’t needed to enable Chile to recover.
The earthquake was caused by the subduction of the Nazca Plate under the South American Plate.
The epicentre of the earthquake was just off the coast of Chile.

Primary effects

500 people were killed.
US$30 billion of damage.

Secondary effects

Coastal areas were flooded by a tsunami.
Landslides blocked some roads.

Responses to the earthquake

A rapid response by emergency services.
Main roads were repaired within a day.
30,000 emergency shelters were built.
A reconstruction plan to help 200,000 households.

1 The Challenge of Natural Hazards

1.1 Natural Hazards

1.1.1 Natural Hazards

1.1.2 Types of Natural Hazards

1.1.3 Factors Affecting Risk

1.1.4 People Affecting Risk

1.1.5 Ability to Cope With Natural Hazards

1.1.6 How Serious Are Natural Hazards?

1.1.7 End of Topic Test - Natural Hazards

1.1.8 Exam-Style Questions - Natural Hazards

1.2 Tectonic Hazards

1.2.1 The Earth's Layers

1.2.2 Tectonic Plates

1.2.3 The Earth's Tectonic Plates

1.2.4 Convection Currents

1.2.5 Plate Margins

1.2.6 Volcanoes

1.2.7 Volcano Eruptions

1.2.8 Effects of Volcanoes

1.2.9 Primary Effects of Volcanoes

1.2.10 Secondary Effects of Volcanoes

1.2.11 Responses to Volcanic Eruptions

1.2.12 Immediate Responses to Volcanoes

1.2.13 Long-Term Responses to Volcanoes

1.2.14 Earthquakes

1.2.15 Earthquakes at Different Plate Margins

1.2.16 What is an Earthquake?

1.2.17 Measuring Earthquakes

1.2.18 Immediate Responses to Earthquakes

1.2.19 Long-Term Responses to Earthquakes

1.2.20 Case Studies: The L'Aquila Earthquake

1.2.21 Case Studies: The Kashmir Earthquake

1.2.22 Earthquake Case Study: Chile 2010

1.2.23 Earthquake Case Study: Nepal 2015

1.2.24 Reducing the Impact of Tectonic Hazards

1.2.25 Protecting & Planning

1.2.26 Living with Tectonic Hazards 2

1.2.27 End of Topic Test - Tectonic Hazards

1.2.28 Exam-Style Questions - Tectonic Hazards

1.2.29 Tectonic Hazards - Statistical Skills

1.3 Weather Hazards

1.3.1 Winds & Pressure

1.3.2 The Global Atmospheric Circulation Model

1.3.3 Surface Winds

1.3.4 UK Weather Hazards

1.3.5 Changing Weather in the UK

1.3.6 Tropical Storms

1.3.7 Tropical Storm Causes

1.3.8 Features of Tropical Storms

1.3.9 The Structure of Tropical Storms

1.3.10 The Effect of Climate Change on Tropical Storms

1.3.11 The Effects of Tropical Storms

1.3.12 Responses to Tropical Storms

1.3.13 Reducing the Effects of Tropical Storms

1.3.14 Tropical Storms Case Study: Katrina

1.3.15 Tropical Storms Case Study: Haiyan

1.3.16 UK Weather Hazards Case Study: Somerset 2014

1.3.17 End of Topic Test - Weather Hazards

1.3.18 Exam-Style Questions - Weather Hazards

1.3.19 Weather Hazards - Statistical Skills

1.4 Climate Change

1.4.1 Climate Change

1.4.2 Evidence for Climate Change

1.4.3 Natural Causes of Climate Change

1.4.4 Human Causes of Climate Change

1.4.5 Effects of Climate Change on the Environment

1.4.6 Effects of Climate Change on People

1.4.7 Climate Change Mitigation Strategies

1.4.8 Adaptation to Climate Change

1.4.9 End of Topic Test - Climate Change

1.4.10 Exam-Style Questions - Climate Change

1.4.11 Climate Change - Statistical Skills

2 The Living World

2.1 Ecosystems

2.1.1 Ecosystems

2.1.2 Food Chains & Webs

2.1.3 Ecosystem Cascades

2.1.4 Global Ecosystems

2.1.5 Ecosystem Case Study: Freshwater Ponds

2.2 Tropical Rainforests

2.2.1 Tropical Rainforests

2.2.2 Interdependence of Tropical Rainforests

2.2.3 Adaptations of Plants to Rainforests

2.2.4 Adaptations of Animals to Rainforests

2.2.5 Biodiversity of Tropical Rainforests

2.2.6 Deforestation

2.2.7 Impacts of Deforestation

2.2.8 Case Study: Deforestation in the Amazon Rainforest

2.2.9 Why Protect Rainforests?

2.2.10 Sustainable Management of Rainforests

2.2.11 Case Study: Malaysian Rainforest

2.2.12 End of Topic Test - Tropical Rainforests

2.2.13 Exam-Style Questions - Tropical Rainforests

2.2.14 Deforestation - Statistical Skills

2.3 Hot Deserts

2.3.1 Hot Deserts

2.3.2 Interdependence in Hot Deserts

2.3.3 Adaptation of Plants to Hot Deserts

2.3.4 Adaptation of Animals to Hot Deserts

2.3.5 Biodiversity in Hot Deserts

2.3.6 Case Study: Sahara Desert

2.3.7 Desertification

2.3.8 Reducing the Risk of Desertification

2.3.9 Case Study: Thar Desert

2.3.10 End of Topic Test - Hot Deserts

2.3.11 Exam-Style Questions - Hot Deserts

2.4 Tundra & Polar Environments

2.4.1 Overview of Cold Environments

2.4.2 Interdependence of Cold Environments

2.4.3 Adaptations of Plants to Cold Environments

2.4.4 Adaptations of Animals to Cold Environments

2.4.5 Biodiversity in Cold Environments

2.4.6 Case Study: Alaska

2.4.7 Sustainable Management

2.4.8 Case Study: Svalbard

2.4.9 End of Topic Test - Tundra & Polar Environments

2.4.10 Exam-Style Questions - Cold Environments

3 Physical Landscapes in the UK

3.1 The UK Physical Landscape

3.1.1 The UK Physical Landscape

3.1.2 Examples of the UK's Landscape

3.2 Coastal Landscapes in the UK

3.2.1 Types of Wave

3.2.2 Weathering

3.2.3 Mass Movement

3.2.4 Processes of Erosion

3.2.5 Wave-Cut Platforms

3.2.6 Headlands & Bays

3.2.7 Caves, Arches & Stacks

3.2.8 Longshore Drift

3.2.9 Sediment Transport

3.2.10 Deposition

3.2.11 Spits, Bars & Sand Dunes

3.2.12 Coastal Management - Hard Engineering

3.2.13 Coastal Management - Soft Engineering

3.2.14 Case Study: Landforms on the Dorset Coast

3.2.15 Coastal Management - Managed Retreat

3.2.16 Coastal Management Case Study - Holderness

3.2.17 Coastal Management Case Study: Swanage

3.2.18 Coastal Management Case Study - Lyme Regis

3.2.19 End of Topic Test - Coastal Landscapes in the UK

3.2.20 Exam-Style Questions - Coasts

3.3 River Landscapes in the UK

3.3.1 The Long Profile of a River

3.3.2 The Cross Profile of a River

3.3.3 Vertical & Lateral Erosion

3.3.4 River Valley Case Study - River Tees

3.3.5 Processes of Erosion

3.3.6 Sediment Transport

3.3.7 River Deposition

3.3.8 Waterfalls & Gorges

3.3.9 Interlocking Spurs

3.3.10 Meanders

3.3.11 Oxbow Lakes

3.3.12 Floodplains

3.3.13 Levees

3.3.14 Estuaries

3.3.15 Case Study: The River Clyde

3.3.16 River Management

3.3.17 Hydrographs

3.3.18 Flood Defences - Hard Engineering

3.3.19 Flood Defences - Soft Engineering

3.3.20 River Management Case Study - Boscastle

3.3.21 River Management Case Study - Banbury

3.3.22 End of Topic Test - River Landscapes in the UK

3.3.23 Exam-Style Questions - Rivers

3.4 Glacial Landscapes in the UK

3.4.1 The UK in the Last Ice Age

3.4.2 Glacial Processes

3.4.3 Glacial Landforms Caused by Erosion

3.4.4 Tarns, Corries, Glacial Troughs & Truncated Spurs

3.4.5 Types of Moraine

3.4.6 Drumlins & Erratics

3.4.7 Snowdonia

3.4.8 Land Use in Glaciated Areas

3.4.9 Conflicts in Glacial Landscapes

3.4.10 Tourism in Glacial Landscapes

3.4.11 Coping with Tourism Impacts in Glacial Landscapes

3.4.12 Case Study - Lake District

3.4.13 End of Topic Test - Glacial Landscapes in the UK

3.4.14 Exam-Style Questions - Glacial Landscapes

4 Urban Issues & Challenges

4.1 Urban Issues & Challenges

4.1.1 Urbanisation

4.1.2 Factors Causing Urbanisation

4.1.3 Megacities

4.1.4 Urbanisation Case Study: Lagos

4.1.5 Urbanisation Case Study: Rio de Janeiro

4.1.6 UK Cities

4.1.7 Case Study: Urban Regen Projects - Manchester

4.1.8 Case Study: Urban Change in Liverpool

4.1.9 Case Study: Urban Change in Bristol

4.1.10 Sustainable Urban Life

4.1.11 Reducing Traffic Congestion

4.1.12 End of Topic Test - Urban Issues & Challenges

4.1.13 Exam-Style Questions - Urban Issues & Challenges

4.1.14 Urban Issues -Statistical Skills

5 The Changing Economic World

5.1 The Changing Economic World

5.1.1 Measuring Development

5.1.2 Limitations of Developing Measures

5.1.3 Classifying Countries Based on Wealth

5.1.4 The Demographic Transition Model

5.1.5 Stages of the Demographic Transition Model

5.1.6 Physical Causes of Uneven Development

5.1.7 Historical Causes of Uneven Development

5.1.8 Economic Causes of Uneven Development

5.1.9 Consequences of Uneven Development

5.1.10 How Can We Reduce the Global Development Gap?

5.1.11 Case Study: Tourism in Kenya

5.1.12 Case Study: Tourism in Jamaica

5.1.13 Case Study: Economic Development in India

5.1.14 Case Study: Aid & Development in India

5.1.15 Case Study: Economic Development in Nigeria

5.1.16 Case Study: Aid & Development in Nigeria

5.1.17 End of Topic Test - The Changing Economic World

5.1.18 Exam-Style Questions - The Changing Economic World

5.1.19 Changing Economic World - Statistical Skills

5.2 Economic Development in the UK

5.2.1 Causes of Economic Change in the UK

5.2.2 The UK's Post-Industrial Economy

5.2.3 The Impacts of UK Industry on the Environment

5.2.4 Change in the UK's Rural Areas

5.2.5 Transport in the UK

5.2.6 The North-South Divide

5.2.7 Regional Differences in the UK

5.2.8 The UK's Links to the World

6 The Challenge of Resource Management

6.1 Resource Management

6.1.1 Global Distribution of Resources

6.1.2 Uneven Distribution of Resources

6.1.3 Food in the UK

6.1.4 Agribusiness

6.1.5 Demand for Water in the UK

6.1.6 Water Pollution in the UK

6.1.7 Matching Supply & Demand of Water in the UK

6.1.8 The UK's Energy Mix

6.1.9 Issues with Sources of Energy

6.1.10 Resource Management - Statistical Skills

6.2.1 Areas of Food Surplus & Food Deficit

6.2.2 Increasing Food Consumption

6.2.3 Food Supply & Food Insecurity

6.2.4 Impacts of Food Insecurity

6.2.5 Increasing Food Supply

6.2.6 Case Study: Thanet Earth

6.2.7 Creating a Sustainable Food Supply

6.2.8 Case Study: Agroforestry in Mali

6.2.9 End of Topic Test - Food

6.2.10 Exam-Style Questions - Food

6.2.11 Food - Statistical Skills

6.3.1 Water Surplus & Water Deficit

6.3.2 Increasing Water Consumption

6.3.3 What Affects the Availability of Water?

6.3.4 Impacts of Water Insecurity

6.3.5 Increasing Water Supplies

6.3.6 Case Study: Water Transfer in China

6.3.7 Sustainable Water Supply

6.3.8 Case Study: Kenya's Sand Dams

6.3.9 Case Study: Lesotho Highland Water Project

6.3.10 Case Study: Wakel River Basin Project

6.3.11 Exam-Style Questions - Water

6.3.12 Water - Statistical Skills

6.4.1 Global Demand for Energy

6.4.2 Increasing Energy Consumption

6.4.3 Factors Affecting Energy Supply

6.4.4 Impacts of Energy Insecurity

6.4.5 Increasing Energy Supply - Solar

6.4.6 Increasing Energy Supply - Water

6.4.7 Increasing Energy Supply - Wind

6.4.8 Increasing Energy Supply - Nuclear

6.4.9 Increasing Energy Supply - Fossil Fuels

6.4.10 Carbon Footprints

6.4.11 Energy Conservation

6.4.12 Case Study: Rice Husks in Bihar

6.4.13 Exam-Style Questions - Energy

6.4.14 Energy - Statistical Skills

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Earthquake had surprising ecological effects in Chile

Yet that’s exactly what researchers found in a study of the sandy beaches of south central Chile, after an 8.8-magnitude earthquake and devastating tsunami in 2010.

Their study also revealed a preview of the problems wrought by sea level rise–a major symptom of climate change.

In a scientific first, researchers from Southern University of Chile and the University of California, Santa Barbara (UCSB) were able to document the before-and-after ecological impacts of such cataclysmic occurrences.

A paper appearing today in the journal PLoS ONE details the surprising results of their study, pointing to the potential effects of natural disasters on sandy beaches worldwide.

The study is said to be the first-ever quantification of earthquake and tsunami effects on sandy beach ecosystems along a tectonically active coastal zone.

“So often you think of earthquakes as causing total devastation, and adding a tsunami on top of that is a major catastrophe for coastal ecosystems,” said Jenny Dugan, a biologist at UCSB.

“As expected, we saw high mortality of intertidal life on beaches and rocky shores, but the ecological recovery at some of our sandy beach sites was remarkable.

“Plants are coming back in places where there haven’t been plants, as far as we know, for a very long time. The earthquake created sandy beach habitat where it had been lost. This is not the initial ecological response you might expect from a major earthquake and tsunami.”

Their findings owe a debt to serendipity.

The researchers were knee-deep in a study supported by FONDECYT in Chile and the U.S. National Science Foundation’s (NSF) Santa Barbara Coastal Long-Term Ecological Research (LTER) site of how sandy beaches in Santa Barbara and south central Chile respond, ecologically, to man-made armoring such as seawalls and rocky revetments.

By late January, 2010, they had surveyed nine beaches in Chile.

The earthquake hit in February.

Recognizing a unique opportunity, the scientists changed gears and within days were back on the beaches to reassess their study sites in the catastrophe’s aftermath.

They’ve returned many times since, documenting the ecological recovery and long-term effects of the earthquake and tsunami on these coastlines, in both natural and human-altered settings.

“It was fortunate that these scientists had a research program in the right place–and at the right time–to allow them to determine the responses of coastal species to natural catastrophic events,” said David Garrison, program director for NSF’s coastal and ocean LTER sites.

The magnitude and direction of land-level change resulting from the earthquake and exacerbated by the tsunami brought great effects, namely the drowning, widening and flattening of beaches.

The drowned beach areas suffered mortality of intertidal life; the widened beaches quickly saw the return of biota that had vanished due to the effects of coastal armoring.

“With the study in California and Chile, we knew that building coastal defense structures, such as seawalls, decreases beach area, and that a seawall results in the decline of intertidal diversity,” said lead paper author Eduardo Jaramillo of the Universidad Austral de Chile.

“But after the earthquake, where significant continental uplift occurred, the beach area that had been lost due to coastal armoring has now been restored,” said Jaramillo. “And the re-colonization of the mobile beach fauna was underway just weeks afterward.”

The findings show that the interactions of extreme events with armored beaches can produce surprising ecological outcomes. They also suggest that landscape alteration, including armoring, can leave lasting footprints in coastal ecosystems.

“When someone builds a seawall, beach habitat is covered up with the wall itself, and over time sand is lost in front of the wall until the beach eventually drowns,” said Dugan.

“The semi-dry and damp sand zones of the upper and mid-intertidal are lost first, leaving only the wet lower beach zones. This causes the beach to lose diversity, including birds, and to lose ecological function.”

Sandy beaches represent about 80 percent of the open coastlines globally, said Jaramillo.

“Beaches are very good barriers against sea level rise. They’re important for recreation–and for conservation.”

Republished with permission from the National Science Foundation .

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U.S. Geological Survey Open-File Report 2011–1053, version 1.1

In cooperation with The American Red Cross

Report on the 2010 chilean earthquake and tsunami response, by the american red cross multidisciplinary team.

First posted March 18, 2011

PDF (18 MB) PDF (downsampled to 300 dpi; 1.7 MB)
USGS Multi-Hazard Demonstration Project

The delegation was hosted by the Chilean Red Cross and received extensive briefings from both national and local Red Cross officials. During nine days in Chile, the delegation also met with officials at the national, regional, and local government levels. Technical briefings were received from the President’s Emergency Committee, emergency managers from ONEMI (comparable to FEMA), structural engineers, a seismologist, hospital administrators, firefighters, and the United Nations team in Chile. Cities visited include Santiago, Talca, Constitución, Concepción, Talcahuano, Tumbes, and Cauquenes. The American Red Cross Multidisciplinary Team consisted of subject matter experts, who carried out special investigations in five Teams on the (1) science and engineering findings, (2) medical services, (3) emergency services, (4) volunteer management, and (5) executive and management issues (see appendix A for a full list of participants and their titles and teams). While developing this delegation, it was clear that a multidisciplinary approach was required to properly analyze the emergency response, technical, and social components of this disaster. A diverse and knowledgeable delegation was necessary to analyze the Chilean response in a way that would be beneficial to preparedness in California, as well as improve mitigation efforts around the United States.

By most standards, the Maule earthquake was a catastrophe for Chile. The economic losses totaled $30 billion USD or 17% of the GDP of the country. Twelve million people, or ¾ of the population of the country, were in areas that felt strong shaking. Yet only 521 fatalities have been confirmed, with 56 people still missing and presumed dead in the tsunami.

The Science and Technology Team evaluated the impacts of the earthquake on built environment with implications for the United States. The fires following the earthquake were minimal in part because of the shutdown of the national electrical grid early in the shaking. Only five engineer-designed buildings were destroyed during the earthquake; however, over 350,000 housing units were destroyed. Chile has a law that holds building owners liable for the first 10 years of a building’s existence for any losses resulting from inadequate application of the building code during construction. This law was cited by many our team met with as a prime reason for the strong performance of the built environment. Overall, this earthquake demonstrated that strict building codes and standards could greatly reduce losses in even the largest earthquakes. In the immediate response to the earthquake and tsunami, first responders, emergency personnel, and search and rescue teams handled many challenges. Loss of communications was significant; many lives were lost and effective coordination to support life-sustaining efforts was gravely impacted due to a lack of inter- and intra-agency coordination.

The Health and Medical Services Team sought to understand the medical disaster response strategies and operations of Chilean agencies, including perceived or actual failures in disaster preparation that impacted the medical disaster response; post-disaster health and medical interventions to save lives and limit suffering; and the lessons learned by public health and medical personnel as a result of their experiences. Despite devastating damage to the health care and civic infrastructure, the health care response to the Chilean earthquake appeared highly successful due to several factors. Like other first responders, the medical community had the ability and resourcefulness to respond without centralized control in the early response phase. The health care community maintained patient care under austere conditions, despite many obstacles that could have prevented such care. National and international resources were rapidly mobilized to support the medical response.

The Emergency Services Team sought to collect information on all phases of emergency management (preparedness, mitigation, response, and recovery) and determine what worked well and what could be improved upon. The Chileans reported being surprised that they were not as ready for this event as they thought they were. The use of mass care sheltering was limited, given the scope of the disaster, because of the resiliency of the population. The impacts of the earthquake and the tsunami were quite different, as were the needs of urban and rural dwellers, necessitating different response activities.

The Volunteer Services Team examined the challenges faced in mobilizing a large number of volunteers to assist in the aftermath of a disaster of this scale. One of the greatest challenges expressed was difficulty in communication; the need for redundancy in communication mechanisms was cited. The flexibility and ability to work autonomously by the frontline volunteers was a significant factor in effective response. It was also important for volunteer leadership to know the emergency plans. These plans need to be flexible, include alternative options, and be completed in conjunction with local officials and other volunteers. The Executive/Red Cross Management Team took a broad look at the impacts of the earthquake and the implications for California. Some of the most important preparation for the disaster came from relationships formed before the event. The communities with strong connections between different government services generally fared well. The initial response and resilience of individuals and communities was another important component. Communication system failures limited the ability of a central government to assist impacted communities, or to issue tsunami warnings. It also delayed the response since the government did not know (in some case for several days) the impact and needs of local governments. In general, plans for congregate care shelters existed but were little used as most people chose to stay at damaged homes or with relatives. Looting was a surprise to response officials as well as social scientists, but both public and private sector organizations, including NGOs (Non-Governmental Organizations), must consider security for damaged businesses as a priority in California’s multihazard planning. Class and ethnic divisions that become heightened during some cases of actual or perceived injustice may also emerge in natural disasters in California.

Several factors contributed overall to the low casualty rate and rapid recovery. A major factor is the strong building code in Chile and its comprehensive enforcement. In particular, Chile has a law that holds building owners accountable for losses in a building they build for 10 years. A second factor was the limited number of fires after the earthquake. In the last few California earthquakes, 60% of the fires were started by electrical problems, so the rarity of fires may have been affected by the shut down of the electricity grid early in the earthquake. Third, in many areas, the local emergency response was very effective. The most effective regions had close coordination between emergency management, fire, and police and were empowered to respond without communication with the capital. The fourth factor was the overall high level of knowledge about earthquakes and tsunamis by much of the population that helped them respond more appropriately after the event.

Suggested citation:

American Red Cross Multi-Disciplinary Team, 2011, Report on the 2010 Chilean earthquake and tsunami response: U.S. Geological Survey Open-File Report 2011-1053, v. 1.1, 68 p., available at https://pubs.usgs.gov/of/2011/1053/.

1.0 Executive Summary

2.0 Introduction

3.0 Science and Technology

4.0 Emergency Management

5.0 Health Services

6.0 Volunteer Management

7.0 Executive Management

8.0 Recommendations for California

9.0 Recommendations for the American Red Cross

10.0 Sources and Acknowledgments

11.0 Appendices

12.0 Glossary of Terms including Acronyms

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Comparing the Chile 2010 and Nepal 2015 earthquakes

by Catherine Owen

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How did Nepalis experience the 2015 earthquake?

Nepal Earthquake: Great Earthquake in Nepal

by Ram Kumar Panday, published by Paradise Publication, (2015), 9789937299480

How tourists experienced the 2015 earthquake

The Earth Moved: Surviving the 2015 Nepal Earthquake

by Row Smith, published by Story Terrace, (2016), 9781540868190

What happened in the Chile 2010 earthquake?

Maule, Chile Earthquake: Assessed through the lens of disaster, risk, and management

published by USC, (2021)

How Chile rebuilt so successfully after the 2010 earthquake

The rebuilding of Chile’s Constitución: how a ‘dead city’ was brought back to life

by Gideon Long, published by The Guardian, (2015)

How Nepal is still trying to rebuild

Nepal: First came the earthquake, then came the debt

by Stephen Starr, published by The Guardian, (2018)

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The Social, Political and Economic Aftershocks of the Chilean Earthquake

March 10, 2010 • 11 min read.

The recent earthquake in Chile -- and the subsequent tsunami -- tested the government of President Michelle Bachelet in terms of how well it could manage a large-scale crisis, just when Bachelet was about to hand over her office to the country’s newly elected leader, Sebastian Piñera. Clearly, the Piñera administration has a titanic task ahead of it. The disaster left Chile with hundreds of people dead or missing, and it has affected the infrastructure of the country as well as its quality of life. Property and sources of employment have been lost. What consequences will the earthquake have for Chile’s economy? And what steps will the Piñera administration need to take in order to help get the country back on its feet?

Public Policy

On February 27, a large number of ports, towns and large cities along Chile’s south-central coast were devastated by an earthquake measuring 8.8 on the Richter scale, and the tsunami that followed it. The disaster has left a toll of more than 479 people dead and 497 missing, according to the latest official figures.

The day after the catastrophe, the government of President Michelle Bachelet acknowledged in public that it had committed a mistake by not providing timely information to warn of a possible tsunami following the quake. Proper warnings were not provided to maritime authorities, and hundreds of lives were lost. This was a serious reversal for Chile’s first female president, who was about to leave office. On March 11, Sebastian Piñera became the country’s president, putting an end to 20 years of leadership by the so-called Concertacion Party, a coalition of centrist and leftist parties.

The devastating quake and the force of gigantic waves, which in some localities were about 20 meters in height, wiped out service for water, light and gas in the center and south of the country for several days. The survivors in the most heavily hit regions had to wait days for the arrival of teams of rescue and medical workers who brought water, food, and clothing.

Mistakes in Management

These chaotic conditions generated a flood of criticism about the government’s performance from a wide range of social groups, who argued that the response to the national emergency had come too late. “We Chileans were thinking that institutions were better prepared than what we could see,” said Juan Sebastián Montes, professor of strategy and economic sociology at the business school of the Adolfo Ibáñez University. “The way the crisis was managed was worse than what we should have anticipated.”

Montes notes that although no country is truly prepared to deal with an earthquake of a magnitude of eight on the Richter scale, “there are some countries that are better prepared than others, as shown by the enormous destruction in Haiti, which recently experienced an earthquake of a lower magnitude than that of Chile.” The Haitian quake had an intensity of seven on the Richter scale, according to the U.S. Geological Service.

Although Chilean specialists say that structural damage to the country was not as extensive as the damage in Haiti, Chile still has a lot of room for improvement when it comes to taking measures to mitigate these sorts of incidents in the future. “There is no sure system for prevention against tsunamis,” notes Hans Niemeyer, professor of geological sciences at the Universidad Católica del Norte in Chile. It turned out, he adds, that “it was more valuable …for the people in the coastal regions to know how to leave quickly for the hills, once the earthquake occurred.”

The Task of Reconstruction

Experts say that there is no reason why the recent change in the Chilean government should affect the way this crisis is managed in coming weeks. Piñera has already held several working meetings with Bachelet, who has named new managers — regional officials whose backgrounds are more technical than political — in those areas that were most affected by the earthquake. Clearly, the Piñera administration has a titanic task ahead of it. It must transform itself into a government of “national reconstruction,” as Niemeyer notes.

He adds, “Because it is a country with a large territory, the new country’s political leadership will have to strengthen its north-south connectivity through our vertebral column, Highway 5 South, which suffered serious damage. No doubt, the government will have to emphasize anti-earthquake construction projects. We can’t have Chile go without air traffic because the international airport in Santiago collapses. These situations cannot happen again in the future; not with highways, hospitals or airports.”

According to experts, Piñera will have to forget the economic promises he made during the election campaign – higher salaries and lower crime, among others – and deal with more urgent priorities such as the large number of people who remain homeless, especially in those areas most damaged by the catastrophe. “Since many people lost their housing, this is going to produce a significant amount of overcrowding, which has to be dealt with over the short term,” notes Rodrigo Morrás, professor of organizational service management at the Adolfo Ibáñez University’s business school.

The earthquake has not only had a significant economic impact on the country’s infrastructure but it also has had significant social repercussions, such as in the loss of the quality of life of the population because of the destruction of property and material goods. People are now talking about a “social earthquake” in Chile. According to Morrás, “The damage that has been done to possessions and physical assets, particularly those that belong to people who live in the coastal areas that suffered the most damage, will be hard to recover, especially if you consider that these social groups have modest means, fewer [financial] resources, and less access to influential networks for rebuilding their assets.”

In addition, in those coastal locations – the southern regions of O’Higgins, El Maule, and Bío Bío – there were many micro-enterprises that will now have to start from zero, adds Morrás. “We are talking about fishermen, transport workers and merchants who lost their boats, trucks, hotels, restaurants, etc. In other words, the progress they had achieved after years of developing a region with interesting tourist attractions has been wiped out. It is going to take these micro-enterprises time to recover; at least two or three years.”

Nevertheless, Morrás does not rule out the possibility that in the short term, these regions will attract more efficient and larger-scale investments because of their attractiveness to tourists.

Economic Effects

Some analysts have predicted that the earthquake could prevent Chile’s economy from growing during 2010. Initially, economists had been forecasting growth of 5.5% this year, and Piñera had promised to accelerate growth through a forceful governmental program.

For Montes, an earthquake with a magnitude of eight on the Richter scale means a loss of capital, inventory and productivity. It is “a net loss; although it is still too early to quantify the impact, it will certainly be reflected in the quarterly figures. In addition, it is very likely that fiscal spending will increase, so it will be very hard to predict the impact of the catastrophe on the indicators of economic growth.” Early estimates indicate that the damages caused by the earthquake could cost Chile about US$30 billion, the equivalent of 15% of its GDP, but in Montes’ opinion, that figure could wind up being even higher.

In contrast, Mat ías Braun, professor of financial markets and economic development at the Adolfo Ibáñez University’s business school, has a less alarmist view of the financial cost of the quake. “Although the losses generated by the catastrophe are quite significant, generally speaking, people are exaggerating the toll,” he says. “I would estimate a maximum of between US$4 billion and US$8 billon. My estimates could be divided the following way: US$2.5 billion in housing construction – equivalent to the destruction of 20% of the homes in the zones that are most affected; US$1.5 billion in commercial and industrial construction; US$2 billion in road and port construction; US$500 million in machinery and equipment; and another US$500 million in lost inventory.”

Braun asserts that the earthquake could even have a positive impact on job growth – because of [the subsequent] reconstruction efforts – and on the growth of the country “because it will lead to a higher percentage of GDP growth of between 1% and 1.5% for two years, and because of the net effect of the loss of capital and subsequent reconstruction.” Although there would have to be a temporary increase in prices of about 2% in coming months, “the repercussions on the [Chilean] exchange rate should be significantly lower.”

Rafael Romero, professor of corporate finance and business valuation at the Adolfo Ibáñez University’s business school, agrees with Braun’s projections. Romero notes that “rebuilding is necessary, which means that economic activity should soar, leading to growth in construction activity and investments in public works. Financial markets have already reacted by showing increases in the prices of companies involved in construction and inputs for construction, such as cement producers.” The best examples of that upward trend in prices include Cementós Melon, which experienced a gain of 251% in its share price on the Santiago stock exchange in recent days, and Grupo Polpaico (which rose 44%), one of the country’s leading manufacturers of cement and concrete.

Real Estate and Construction Collapse

The shares that plummeted after the earthquake were in real estate and construction firms, following analysts’ observations about the destruction of new buildings and structural damage in other buildings that were no more than three years old but had to be evacuated because of the risk of collapse.

Some experts have been surprised by the collapse of modern buildings, and have questioned the controls of Chile’s anti-seismic regulations. According to the Chilean Chamber of Construction, the country’s industry trade group, buildings must be built to withstand a grade-eight earthquake. “Some companies are managing to avoid those controls,” says Felipe Aguilera, professor of geology at the University of Atacama in northern Chile. “On the other hand, this doesn’t explain the degree of destruction in new buildings, unlike others that are in excellent shape after the earthquake.” The most emblematic case is the 30-floor Millennium Building, in the heart of the Santiago business district, which escaped any damage from the quake.

Insurance companies will have to pay out considerable sums of money to compensate for the damages. Recently, Mikel Uriarte, president of the Chilean insurance association, told the Chilean daily newspaper El Mercurio that the total amount will approach US$4 billion.

Chile’s leading export industry, copper production, should emerge untouched by the quake, which lasted almost three minutes. A few days after the quake occurred, the price of copper reached US$3.32 per pound – 4% higher than the US$3.20 registered before the quake – because of rumors that Chile was not going to be able to comply with its export commitments. However, experts don’t believe that will be the case.

“Copper production will not be affected, because the principal mines for this metal are in the north of the country, where they have not been affected by the earthquake,” says Niemeyer. “Chile is in perfect shape to comply with its export obligations.” Although several ports in the south of the country have suffered structural damages, the port complex in Valparaíso – from which copper exports are shipped – is operating without any problems, the local press reported.

In contrast, Montes notes that other exporting sectors have suffered serious damage to their production capabilities, including agribusiness and fisheries, where crops and fishing fleets have been destroyed.

Lessons Left by the Earthquake

Chile can learn various lessons from this unfortunate episode, which has had so many different repercussions. According to Morrás, one of the key lessons is the importance of speed when it comes to detecting a tsunami and providing warnings. Another lesson is the importance of educating the population about how to behave during an earthquake, “whether you are in your house, inside a car, on the street, along the coast or in a high-rise apartment,” he says. “You also need to improve social and community networks, such as groups of neighbors in communities, buildings and neighborhoods, with the goal of being able to construct a communications and containment network. This is because our country covers such a large territory, and it is very likely that numerous localities will remain isolated [for quite a while] after any quake of great magnitude.”

Morrás adds: “It’s worth emphasizing that the earthquake produced a moral deterioration of the population resulting from the belated response of the authorities to the catastrophe. The slow pace of response created disorder and chaos, which favored such behavior as robberies and lootings in supermarkets and shopping malls. This behavior, in turn, became legitimated by the need for food, water and other basic products. As a result, the [importance of] rapid and effective responsiveness by institutions is another major lesson that you have to derive [from the crisis].”

More recently, the country’s largest companies have joined together with governmental institutions, banks, non-governmental organizations, the communications media, artists and ordinary citizens in a national solidarity campaign called “Chile Helps Chile,” which includes the participation of former President Bachelet and newly elected President Piñera. Over the first 25 hours of the campaign, it managed to collect some US$58 million, to be spent on the construction of emergency housing and schools — to many, a sign of hope that the nation can pull itself together more rapidly than people ever imagined.

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Trust via disasters: the case of Chile's 2010 earthquake

Affiliation.

1 Professor of Economics, Facultad de Gobierno, Universidad del Desarrollo, Santiago de Chile, Chile.
PMID: 25196338
DOI: 10.1111/disa.12077

Chile has a long-standing history of natural disasters and, in particular, earthquakes. The latest big earthquake hit Chile on 27 February 2010 with a magnitude of 8.8 on the Richter scale. As an event that had a profound impact on significant portions of the population, the earthquake could theoretically have served to build trust by promoting new trust networks through the enhancement of distant family ties and the interaction between affected neighbours. This study offers an empirical analysis of this theory in the Chilean case. It finds that if initial social capital is very low (thus allowing for post-disaster looting and violence), then the impact of the trust-increasing effect is smaller. It also shows that the effect of the disaster was not transitory, but that it persisted and actually increased over time.

Keywords: Chile's 2010 earthquake; disaster; economics of disasters; resilience; sociology of disasters; subjective well-being; trust.

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Report on the 2010 Chilean earthquake and tsunami response

In July 2010, in an effort to reduce future catastrophic natural disaster losses for California, the American Red Cross coordinated and sent a delegation of 20 multidisciplinary experts on earthquake response and recovery to Chile. The primary goal was to understand how the Chilean society and relevant organizations responded to the magnitude 8.8 Maule earthquake that struck the region on February 27, 2010, as well as how an application of these lessons could better prepare California communities, response partners and state emergency partners for a comparable situation. Similarities in building codes, socioeconomic conditions, and broad extent of the strong shaking make the Chilean earthquake a very close analog to the impact of future great earthquakes on California. To withstand and recover from natural and human-caused disasters, it is essential for citizens and communities to work together to anticipate threats, limit effects, and rapidly restore functionality after a crisis.

Citation Information

Publication Year	2011
Title	Report on the 2010 Chilean earthquake and tsunami response
DOI
Authors
Publication Type	Report
Publication Subtype	USGS Numbered Series
Series Title	Open-File Report
Series Number	2011-1053
Index ID
Record Source
USGS Organization	Multi-Hazard Demonstration Project

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Nepal Earthquake 2015

A case study of an earthquake in a low income country (LIC).

Nepal, one of the poorest countries in the world, is a low-income country. Nepal is located between China and India in Asia along the Himalayan Mountains.

A map to show the location of Nepal in Asia

What caused the Nepal Earthquake?

The earthquake occurred on a collision plate boundary between the Indian and Eurasian plates.

What were the impacts of the Nepal earthquake?

Infrastructure.

Centuries-old buildings were destroyed at UNESCO World Heritage Sites in the Kathmandu Valley, including some at the Changu Narayan Temple and the Dharahara Tower.
Thousands of houses were destroyed across many districts of the country.

Social and economic

Eight thousand six hundred thirty-two dead and 19,009 injured.
It was the worst earthquake in Nepal in more than 80 years.
People chose to sleep outside in cold temperatures due to the risk of aftershocks causing damaged buildings to collapse.
Hundreds of thousands of people were made homeless, with entire villages flattened.
Harvests were reduced or lost that season.
Economic losses were estimated to be between nine per cent to 50 per cent of GDP by The United States Geological Survey (USGS).
Tourism is a significant source of revenue in Nepal, and the earthquake led to a sharp drop in the number of visitors.
An avalanche killed at least 17 people at the Mount Everest Base Camp.
Many landslides occurred along steep valleys. For example, 250 people were killed when the village of Ghodatabela was covered in material.

What were the primary effects of the 2015 earthquake in Nepal?

The primary effects of the 2015 earthquake in Nepal include:

Nine thousand people died, and 19,000 people were injured – over 8 million people were affected.
Three million people were made homeless.
Electricity and water supplies, along with communications, were affected.
1.4 million people needed support with access to water, food and shelter in the days and weeks after the earthquake
Seven thousand schools were destroyed.
Hospitals were overwhelmed.
As aid arrived, the international airport became congested.
50% of shops were destroyed, affecting supplies of food and people’s livelihoods.
The cost of the earthquake was estimated to be US$5 billion.

What were the secondary effects of the 2015 earthquake in Nepal?

The secondary effects of the 2015 earthquake in Nepal include:

Avalanches and landslides were triggered by the quake, blocking rocks and hampering the relief effort.
At least nineteen people lost their lives on Mount Everest due to avalanches.
Two hundred fifty people were missing in the Langtang region due to an avalanche.
The Kali Gandaki River was blocked by a landslide leading many people to be evacuated due to the increased risk of flooding.
Tourism employment and income declined.
Rice seed ruined, causing food shortage and income loss.

What were the immediate responses to the Nepal earthquake?

India and China provided over $1 billion of international aid .
Over 100 search and rescue responders, medics and disaster and rescue experts were provided by The UK, along with three Chinook helicopters for use by the Nepali government.
The GIS tool “Crisis mapping” was used to coordinate the response.
Aid workers from charities such as the Red Cross came to help.
Temporary housing was provided, including a ‘Tent city’ in Kathmandu.
Search and rescue teams, and water and medical support arrived quickly from China, the UK and India.
Half a million tents were provided to shelter the homeless.
Helicopters rescued people caught in avalanches on Mount Everest and delivered aid to villages cut off by landslides.
Field hospitals were set up to take pressure off hospitals.
Three hundred thousand people migrated from Kathmandu to seek shelter and support from friends and family.
Facebook launched a safety feature for users to indicate they were safe.

What were the long-term responses to the Nepal earthquake?

A $3 million grant was provided by The Asian Development Bank (ADB) for immediate relief efforts and up to $200 million for the first phase of rehabilitation.
Many countries donated aid. £73 million was donated by the UK (£23 million by the government and £50 million by the public). In addition to this, the UK provided 30 tonnes of humanitarian aid and eight tonnes of equipment.
Landslides were cleared, and roads were repaired.
Lakes that formed behind rivers damned by landslides were drained to avoid flooding.
Stricter building codes were introduced.
Thousands of homeless people were rehoused, and damaged homes were repaired.
Over 7000 schools were rebuilt.
Repairs were made to Everest base camp and trekking routes – by August 2015, new routes were established, and the government reopened the mountain to tourists.
A blockade at the Indian border was cleared in late 2015, allowing better movement of fuels, medicines and construction materials.

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AQA Geography GCSE Lessons - Natural Hazards - Effect & Response Chile & Nepal earthquake case study

Subject: Geography

Age range: 14-16

Resource type: Lesson (complete)

Last updated

13 August 2024

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AQA Geography GCSE Double Lesson - Living with the physical environment - Challenges of Natural hazards - Tectonic Hazards - Effects and Responses to an Earthquake - Chile & Nepal earthquake case studies

Students will learn:

about the difference between the effects and responses of earthquakes in contrasting countries. Nepal (Low Income Country) and Chile (Newly Emerging Country)

Primary effects
Secondary effects
Immediate response
Long-term response
Chile earthquake case study
Nepal earthquake case study

This lesson includes

Embedded videos
Differentiation for different abilities
Worksheet and resources for printing

This is a double lesson is suitable for Key Stage 4 AQA GCSE geography students. The lesson is suitable for two 50 minutes - 1 hour lesson.

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AQA Geography GCSE Lesson Bundle - Natural Hazards - All lessons

AQA Geography GCSE - Living with the physical environment - Natural hazards - All lessons Students will learn: * What is a natural hazard * Global distribution of plate boundaries * Physical processes at plate boundaries * Chile & Nepal earthquake case studies * Chile & Nepal Earthquake comparing earthquakes * Reducing the risk of tectonic activity * Living near a volcano This lesson includes * Starters * Embedded videos * Differentiation for different abilities * Worksheet and resources for printing This lesson is suitable for Key Stage 4 AQA GCSE geography students. The lesson is suitable for all eight 50 minutes - 1 hour lesson.

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Unsymmetricity effects on seismic performance of multi-story buildings

Open access
Published: 03 September 2024
Volume 6 , article number 476 , ( 2024 )

Cite this article

You have full access to this open access article

Antony Vimal Paul Pandian 1 ,
Krishna Prakash Arunachalam 2 ,
Alireza Bahrami 3 ,
Lenin Miguel Bendezu Romero 4 ,
Siva Avudaiappan 2 &
Paul O. Awoyera 5

The unsymmetrical configurations in buildings lead to non-uniform distributions in their strength, mass, and stiffness, and they are consequently prone to damage during seismic hazards. In this study, the seismic performance of multi-story buildings with 5, 8, 10, and 12 stories of square, ‘L’, ‘T’, and ‘U’-shaped buildings have been investigated. The research deals with the variation of the natural time periods and how it affects the seismic performance of unsymmetrical multi-story buildings. The coupled and uncoupled equations of motion, based on the symmetricity of the buildings about both axes, were solved to obtain natural time periods that influence the spectral acceleration of the ground accelerations. Six important ground accelerations were considered. Nonlinear static analysis, such as pushover analysis, was also carried out on all the buildings. Comparisons were made on the seismic behavior of both the symmetrical and unsymmetrical structures. The results revealed that the spectral acceleration influences dynamic responses, such as base shear, base moment, base torsion, roof displacement, roof rotation, and story drifts of the buildings. Moreover, it was found that even though the ‘L’-shaped buildings are unsymmetrical about both axes, they are less vulnerable than the ‘T’ and ‘U’-shaped buildings, which are unsymmetrical about one axis.

Article Highlights

Due to non-uniform strength, mass, and stiffness distributions, unsymmetrical building configurations amplify seismic vulnerability.

Study investigates impact of natural time period variations on seismic performance of 5, 8, 10, and 12-story square, ‘L’, ‘T’, and ‘U’-shaped buildings.

Findings show that ‘L’-shaped buildings, despite being unsymmetrical, have lower seismic vulnerability than ‘T’ and ‘U’-shaped buildings.

Unequal strength distribution increases roof displacement under seismic loading.

Varied stiffnesses across structures intensify inter-story drift during earthquakes.

Seismic performance of high-rise buildings with advanced lateral load resisting systems subjected to wind and earthquake loads

Nonlinear Seismic Behavior of Torsional Buildings Designed Based on Force and Displacement Procedures

The Effect of Variation of Stories’ Plan Size along Height of Relatively Tall Steel Buildings on Their Seismic Behavior

Avoid common mistakes on your manuscript.

1 Introduction

An earthquake is the most influencing among the most unpredictable and devastating natural hazards. Multi-story buildings with unsymmetrical configurations are normally constructed nowadays mainly for aesthetic purposes and rapid urbanization growth rate. However, stiffness and mass distribution of such buildings will become non-uniform, and therefore, they will become highly vulnerable during an earthquake. Generally, failures in multi-story buildings made of reinforced concrete are related to structural deficiencies such as quality of materials, detailing, building symmetry, and construction deficiencies. Hence, it is indispensable to evaluate the earthquake behavior of buildings to reduce earthquake-related problems. Over the years, various analytical procedures were developed to ensure the earthquake resistance of the structures whenever they were subjected to significant earthquakes. The earthquake performance of a structure depends on various factors, such as lateral strength, stiffness, and ductility, as well as regular and simple configurations. Out of the above factors, configuration is the important one affecting the performance of a building. Practically, it is rarely possible to have a regular structure, while an irregular structure is very difficult to define. Consequently, a structure’s horizontal and vertical building configurations play a very important role in making it seismic resistant during earthquake excitation. The non-uniform distribution of stiffness and mass causes unwanted amplification of maximum displacement and seismic force concentration in a certain region due to unbalanced torsion during earthquake excitation. It may also cause catastrophe for the structure. Therefore, special attention must be paid to designing an irregular building located in a seismic-prone region. Many seismic code books are available that provide the construction aspects and various design requirements for regular buildings to minimize the effects of earthquakes. But such code books are unavailable for elongated and contracted buildings, high-rise structures, structures with irregular configurations, unsymmetrical structures, structures with vertical structural irregularities, etc.

Unsymmetrical buildings have plan irregularity in either x direction or both x and y directions [ 1 ]. Unsymmetrical structures suffer from more damage due to earthquakes than their symmetrical buildings. Plan irregularity is one of the most common types of irregularity found nowadays. Horizontal resting elements such as large openings, re-entrant corners, cut-outs, and other abrupt changes or plan irregularities result in torsion, stress concentration, and diaphragm deformations. In the current study, ‘L’, ‘T’, ‘U’, and square-shaped buildings have been taken into account to find their seismic performance during earthquakes. Torsional behavior is one of the main factors that produces damage (reached collapse) on the structures. Torsion is induced in buildings mainly because of the arbitrary stiffness and mass distribution. Generally, torsion is developed in an unsymmetrical building when the distance between the story’s center of mass and the story’s center of rigidity is larger than 20% of the plan dimension of the structure in either x or y direction. If torsion irregularity occurs, the resistive and inertia forces will act through the center of rigidity and center of mass, respectively [ 2 ].

Palagala and Singhal [ 3 ] evaluated the earthquake vulnerability of reinforced concrete-framed archetype structures, including vertical irregularity, plan irregularity, short columns, and open-ground stories. HAZUS methodology is used to study the structural score, such as performance point, probability of complete damage, and probability of collapse, of reinforced concrete-framed structure. It was found that the basic score of the reinforced concrete-frame provided with infill made of masonry for the full height was not affected by soil condition.

Khanal and Chaulagain [ 4 ] studied the elastic earthquake behavior of ‘L’-shaped structural frames through irregular plan dimensions. Buildings of structural irregularities lead to the arbitrary distribution of the story drift, additional torsion, etc., and according to the irregularity type, the structure could fail during an earthquake. The structural responses were measured in terms of story displacement, inter-story drift ratio, torsional irregularity ratio, rotation of torsional diaphragm, normalized base shear, and base moment. This study demonstrated an increase in the irregularity of plan dimensions of the building, which increases the shear force demands, inter-story drifts, and overturning moment at the foundation level.

Kumar and Samanta [ 5 ] observed the seismic fragility valuation of existing buildings made of reinforced concrete. The seismic susceptibility is calculated based on the fragility curve obtained. The fragility of 3, 5, and 9-story reinforced concrete structures was studied. The likelihood of damage for structures with a gravity design was indicated to be higher than for buildings with a special moment-resisting frame. Dalal and Dalal [ 6 ] studied the reinforced concrete moment-resistant frame's strength, deformation, and fragility. The two seismic analysis techniques employed in this work are the force-based design (FBD) approach and the performance-based plastic design (PBPD) method. Analysis has been done on a 20-story reinforced concrete moment resisting frame. The immediate occupancy (IO), life safety (LS), and collapse prevention (CP) performance standards were all taken into consideration when designing these structural frames. It is understood from the results that the PBPD method performs better than the FBD method in terms of fragility and seismic performance. The LS performance level is suggested for design in the PBPD technique. The inelastic torsional response of unsymmetrical, ductile, reinforced concrete structures with a soft first story was assessed by Hareen and Mohan [ 7 ]. The study considers structures of symmetrical rectangular, and unsymmetrical ‘L’, ‘T’, and ‘U’-plan shapes. More seismic demand is placed on the pliable side corner columns of torsionally irregular, ductile buildings with soft first stories. To prevent premature failure of the column, it was established that the design force should be 1.5 times higher than its design value. Zameeruddin and Sangle [ 8 ] discussed the performance-based seismic design. The two main issues are accurate quantification of the unknowns and adequate characterization of the resulting structural destruction for inclusion in the design or performance evaluation technique. Using SAP-2000 software, 15 moment-resisting frames with 4, 6, 8, 10, and 12-story buildings were modeled and investigated with respect to basic periods, roof displacements, inter-story drift ratios, base shears, and modification factors. Eventually, the seismic performance was compared to other limitations.

Sattar [ 9 ] evaluated the consistency of the framed structures made of reinforced concrete between prescriptive and performance-based earthquake design methodologies. ASCE 41 was utilized to assess the behavior of reinforced concrete moment resisting frame structures that are 4 and 8 stories in height and were designed in line with ASCE 7–10 norms. The CP and LS performance ratings were used to investigate each component in the archetypal buildings. The archetype structures outperformed at the LS performance level. Cardone and Flora [ 10 ] conducted an analysis of multiple inelastic mechanisms. Through the use of various engineering demand parameters like inter-story drift ratios and floor accelerations, a structural investigation was done to assess the seismic demand on the structure. A standard 6-story building that typifies reinforced concrete-frame construction was utilized for the analysis. The plastic mechanism illustrated the structural reactions at various intensity levels and drift profile related to yielding and collapse of the structures. Bhaskar and Menon [ 11 ] took various parameters to measure the degree of a building's torsional irregularity. The nonlinear seismic demands on a series of 3D building models were evaluated at various degrees of ground shaking intensity. These models all have similar plan configurations but differ in a variety of ways, including stiffness eccentricity, torsional radius, strength eccentricity, etc. The structures reacted elastically at low intensities. However, it was discovered that strength eccentricity is a superior way to describe torsional irregularity at high-intensity levels in which the building experiences large penetrations into the inelastic behavior.

Dutta et al. [ 12 ] examined reinforced concrete buildings that are between low and mid-rise in terms of seismic susceptibility. The damage level was raised by poor design and construction quality and uneven scattering of infill wall. A straightforward nonlinear static analysis-based method was employed to evaluate fragility of low to mid-height reinforced concrete buildings. The pushover analysis was performed by placing a building under a lateral load that increases monotonically. The findings also pointed out a decline in strength and stiffness of the frame without infill wall and reinforced concrete-framed buildings as well as a decline in design and construction quality. Gautam et al. [ 13 ] investigated the earthquake fragility properties of reinforced concrete buildings damaged by Nepal’s 2015 Gorkha earthquake. The fragility functions depended on in-depth damage inspections of several buildings that were impacted by the earthquake and its aftershocks [ 14 , 15 ]. Fragility functions are important for estimating overall loss, finding weak points in structures, and mitigating overall risk. They are also valuable at the component level. Infill and parapet walls are two examples of non-structural components that are highly brittle than structural ones and represent a safety danger to building occupants in addition to impairing their ability to use the structure as intended.

Dutta et al. [ 16 ] discussed two methods for seismic design of structures. They are the yield point spectra method and the conventional method. The traditional approach maintains stiffness while strength and yield displacement change according to the reduction factor's value. The yield point spectra method is difficult to apply, while the standard method is proven to be safe but unprofitable. The conventional method is suggested, a new iterative strategy that succeeds where the yield spectra-based method fails by producing findings for better ductility. Rahman et al. [ 17 ] compared the analysis, design, and earthquake behavior of reinforced concrete buildings under Bangladesh (BNBC-1993), India (IS 1893), and the United States (ASCE 7–10) seismic design regulations. For all codes, a 12-story reinforced concrete special moment-resisting frame was taken into consideration. When ground excitations meant to reflect the Indian design response spectra were applied, the Indian code performed better. Oggu and Gopikrishna [ 18 ] examined the susceptibility assessment of 3D-reinforced concrete structural frames under bidirectional single and repeated ground motions. According to the findings of this experiment, the likelihood of the reinforced concrete building collapsing during a series of earthquakes is substantially lower than it would be during a single, extremely powerful earthquake. The building must be constructed to withstand the forces of a series of earthquakes. Bhasker and Menon [ 19 ] suggested ground motion intensity measurements (IMs), which exhibit qualities including scaling robustness, effectiveness, sufficiency, and hazard calculability. When compared to those depending on structure-specific measurements, the study’s findings expressed that vector IMs, non-structure-specific IMs, are effective insignificantly at estimating the maximum inter-story drift requirement. Hussain and Dutta [ 20 ] found that unsymmetrical structures display more sensitive inelastic seismic behavior than symmetrical ones due to the connection of torsional and lateral vibration. The study's general conclusions could be utilized to improve the seismic code's allowance for unsymmetrical construction. Unsymmetrical constructions’ torsional and lateral connections make the corner elements more susceptible.

By considering the contributions of higher structural modes, Zain et al. [ 21 ] created analytical fragility relationships for reinforced concrete buildings located in highly earthquake-prone regions to minimize computing effort. A comparison of the fragility curves generated by the two techniques was made. The findings demonstrated the efficacy, rigidity, and ease of the established approach for conducting susceptibility calculations without compromising accuracy. For the earthquake design of acceleration-sensitive non-structural components in a building, Surana et al. [ 22 ] investigated the floor response spectrum, which was employed to calculate the design floor acceleration. The suggested model to calculate damping modification factors for the elastic floor response spectrum can be used with both the current performance-based earthquake design of non-structural components placed in inelastic building structures and the code-based seismic design. Jalilkhani et al. [ 23 ] made a new multi-mode adaptive pushover analysis process to calculate the seismic requirements of reinforced concrete moment-resisting frames. It has been done to analyze four unique reinforced concrete moment resisting building frames with 4, 8, 12, and 20 stories. The findings demonstrated that the multi-mode adaptive pushover analysis process technique can provide an advanced nonlinear static process that is satisfactory for assessing the earthquake behavior of reinforced concrete moment-resisting building frames. In the SPEAR building and the 9-story building, Belejo and Bento [ 24 ] looked into the improved modal pushover analysis. A multi-mode method called improved modal pushover analysis offers the benefit of redefining the lateral load imposed. Top displacement ratio, pushover capacity curves, lateral displacement profile, normalized top displacement, inter-story drift, and shear force were employed to assess both structures' seismic vulnerability. Daei and Poursha [ 25 ] examined the possibility of applying and soundness of enhanced pushover processes in evaluating the earthquake requirements of mid- and high-rise reinforced concrete structural frames under pulse-like far-fault and near-fault ground excitations. The earthquake demands of reinforced concrete building frames can be reasonably predicted using MPA, EN2, and SMP techniques.

Depending on the 3D performance of a normal three-story reinforced concrete structural frame, Xu and Gardoni [ 26 ] provided probabilistic earthquake demand and capacity models. IO, LS, and CP are the three performance levels. This study compared the proposed 3D fragility analysis results to those of the conventional 2D fragility analysis. Cando et al. [ 27 ] investigated how stiffness of buildings made of shear walls constructed in accordance with present Chilean rules affected their earthquake performance. Buildings’ over-strength and displacement ductility were estimated using pushover analyses, while fragility curves were estimated utilizing incremental dynamic analyses. It was concluded that increasing stiffness enhances the response performance of structures made of reinforced concrete shear wall. Depending on the advocated seismic vulnerability index (SVI) methodology, Kassem et al. [ 28 ] suggested a simplified method for assessing the earthquake risk of reinforced concrete buildings. Building frame failure mechanism and the formation of plastic hinges are noted by gradual stress increment. SVI is used to quantify earthquake-related damage to buildings. Zhang and Tian [ 29 ] suggested a more straightforward, performance-based, and ideal earthquake design approach for reinforced concrete moment resisting frames that span multiple stories. The design outcomes indicated that compared to the initial design based on strength, 26% of necessary cross-sectional dimensions and 30% of flexural strength can be lowered. The optimized structure was subjected to nonlinear time-history studies utilizing 10 ancient ground accelerations scaled to three levels of earthquake endangerment. The earthquake behavior of four overhead water tanks with several factors, mainly lateral stiffness was evaluated [ 30 ], and it was discovered that, compared to filled tanks, empty tanks are far more susceptible to the effects of earthquakes, but this vulnerability might be reduced by providing base isolation. Vimal et al. [ 31 ] were involved in finding out the efficacy of base isolation in 5-story buildings of different fundamental natural time periods, and it was resulted that better performance of the building of lower fundamental natural time periods could be obtained if base isolation were provided.

Li et al. [ 32 ] evaluated seismic vulnerability of regional group structures using Wenchuan earthquake data from 2008, developing a seismic risk experience database and establishing empirical vulnerability matrices for six types of buildings. A multifactor vulnerability innovation comparison model was made, revealing a decreasing trend in damage with increasing intensity. Si-Qi and Jian [ 33 ] reported a quantitative method and innovative model considering composite seismic intensity indicators for estimating regional bridges’ seismic risk and vulnerability. The model was updated and validated using 300,000 acceleration records from the Luding earthquake in China, and a vulnerability prediction model was developed using nonlinear regression methods. Si-Qi [ 34 ] achieved a novel method for rapidly predicting structural vulnerability utilizing fuzzy decision-making and hierarchical systems. It established rapid fragility prediction models for typical structures, considering multivariate fuzzy membership index. The model considered multiple fuzzy membership parameters and structural earthquake damage database.

Si-Qi et al. [ 35 ] proposed a method for assessing seismic risk in urban masonry structures, based on real acceleration records from the Wenchuan earthquake in 2008. The model employed an updated vulnerability level and an innovative seismic risk membership index algorithm, improving the accuracy of seismic risk estimation for masonry structures. Li [ 36 ] combined numerical model algorithms with empirical vulnerability methods to develop a prediction model for estimating the fragility of reinforced concrete structures. It used data from the Wenchuan earthquake in China in 2008 and numerical simulation analysis to validate the model's accuracy. The study explored damage modes under different intensities. Li [ 37 ] analyzed seismic vulnerability of regional structures during a destructive earthquake in China, analyzing 300,000 acceleration records. It developed an updated structural seismic vulnerability model, a membership index function, and a multidimensional failure prediction model based on an improved mean seismic damage index.

Ruggieri and Vukobratović [ 38 ] evaluated acceleration demands in low-rise reinforced concrete buildings with torsion using peak floor accelerations and floor response spectra. The aim was to provide empirical formulas to quantify amplification effects due to torsion in existing and new reinforced concrete buildings. Eight archetype buildings were selected, and numerical models were considered in both linear elastic and nonlinear configurations. The study found that the change of demands depends on the position of the non-structural components and distance between the center of rigidity and center of mass. Ruggieri and Uva [ 39 ] examined the extension of linear analysis concepts to nonlinear static analysis procedures in new generation building codes. Nonlinear static analysis is widely employed to assess seismic performance of new and existing buildings but has limitations. Recent upgrades of building codes, like the Italian one, provide different rules for nonlinear static procedures, including the use of a horizontal load profile proportional to story forces. The study investigates the seismic behavior of archetype buildings with increasing height irregularity, using both traditional and new load profiles. The analysis campaign indicates the efficiency of the new load profile and answers the question of whether response spectrum analysis should be extended to nonlinear static analysis.

Based on the past research, it is understood that unsymmetrical plan structures are underperforming than symmetrical structures, and there is hardly any research which concentrates on variation of fundamental natural time period, which is responsible for the dynamic response, and natural time periods of subsequent modes corresponding to various unsymmetrical buildings. Therefore, this research focuses on how natural time period varies based on the type of unsymmetrical buildings.

2 Unsymmetrical buildings

This study examines seismic performance of unsymmetrical shaped buildings such as ‘L’, ‘T’, ‘U’ and symmetrical square-shaped buildings. The plan irregularity is taken as major parameter in the buildings. The plan was drawn in AutoCAD software and is presented in Fig. 1 a—d. The bare frame of the square, ‘L’, ‘T’, and ‘U’-shaped buildings with 5, 8, 10, and 12 stories was developed in the finite element software, ETABS, and the 12-story buildings are depicted in Fig. 2 . The aforementioned buildings with different 5, 8, 10, and 12 stories are considered for analyzing how other stories of the same building influence seismic performance due to earthquakes. The square-shaped building is treated as reference model as it is regular in mass, stiffness, and strength. The frame selected for the study is special moment-resisting frame. The center of mass and center of rigidity of the irregular buildings do not coincide. On considering ‘N’ as the number of stories, the square-shaped buildings will have ‘N’ degrees of freedom (DOF) as they are symmetrical about both axes and the ‘T’ and ‘U’-shaped buildings will have ‘2N’ DOF as they are symmetrical only with respect to x axis. Meanwhile, the ‘L’-shaped buildings have ‘3N’ DOF as they are unsymmetrical about both axes. The total seismic weight of structure is taken as 25% of live load and 100% of dead load [ 41 , 42 , 43 ]. The concrete mix for all elements is M30 grade and Fe415 rebars were used as longitudinal and confinement reinforcement. The other structural properties, applicable to all the buildings, are listed in Table 1 .

a – d . Plans of various unsymmetrical buildings

12-story buildings: a square shape, b ‘L’ shape, c ‘T’ shape, and d ‘U’ shape

Walls are crucial elements in buildings, providing lateral stiffness and contributing significantly to the overall structural behavior. Despite not being prominently presented in figures or diagrams, their presence and influence are typically accounted for in the analytical models and calculations. The exclusion of walls from visual representations or figures does not invalidate the archetype’s representation of real-life cases. Instead, it focuses on specific aspects of interest (e.g., plan irregularity and seismic response) while assuming that wall effects are adequately accounted for in the analytical models. Real-life buildings often have complex geometries and structural configurations that may not be fully captured in archetype models. However, archetype buildings are designed to be representative enough to draw meaningful conclusions about structural behavior and performance.

In this research, the archetype reinforced concrete buildings primarily focused on the structural response of reinforced concrete frames under seismic loading conditions. The inclusion of masonry infills was not explicitly modeled in the archetype buildings analyzed. The study aimed to investigate the torsional effects and nonlinear behavior of reinforced concrete structures, focusing on frame elements without incorporating secondary elements like masonry infills. But, the seismic weight of the masonry walls was calculated and considered at each floor level. This approach was chosen to simplify the analysis and isolate the effects of primary structural components. The study focused on capturing ductile behavior in reinforced concrete structures, characterized by significant deformations and energy dissipation capacity beyond yield. This was achieved through the definition of plastic hinges with appropriate yielding force (V y ) and ductility parameters (µ). The modeling approach allowed for the simulation of post-peak behavior, essential for understanding structural response under seismic events. Brittle failure mechanisms, such as shear failures, were not explicitly modeled in this analysis [ 38 ] .

3 Equation of motion of unsymmetrical building

Table 2 outlines the various parameters used for development of the numerical model.

Building frames in the y axis of an ‘L’-shaped unsymmetrical plan are positioned at an eccentric distance ('e') from the diaphragm's center of mass, whereas frames in the x axis are set at an eccentric distance ('d') from the same location. 3DOF, such as roof displacement in ux in the x direction, uy in the y direction, and torsional rotation in u θ in the z direction about the vertical axis, are used to characterize the motion of the roof mass. The x, y, and z axis components of the following equation of motion from Eq. ( 1.1 ) are coupled based on the orientation of frames about the center of mass.

The x axis frames of ‘U’ and ‘T’-shaped unsymmetrical plan buildings are symmetrical about the diaphragm center, while the y axis orientation of the frames is unsymmetrical. This indicates that the structure's response to ground motion in the x direction can be ascertained by solving the single degree of freedom (SDF) system equation. The equation for the 2DOF system, which is represented in Eq. ( 1.2 ), may be solved to find the coupled lateral torsional response of the structure to the ground motion in the y direction.

Symmetrical plan building can be analyzed independently in the two lateral directions of ground motions. The stiffness matrix can be found using a static condensation technique, while the mass matrix is a diagonal matrix containing lumped masses. The equation of motions is uncoupled because the frames are symmetrical about the x and y axes. This means that translation ground motion in either direction would only cause lateral motion of the system in that direction. Equation ( 1.3 ) can be employed to solve for the response to each component of ground motion separately. The first line of Eq. ( 1.3 ), i.e., $\left[m\right]\left[{\ddot{u}}_{x}\right]+\left[{k}_{xx}\right]\left[{u}_{x}\right]=-[m{\ddot{u}}_{gx}\left(t\right)]$ is the traditional basic equation of motion used for obtaining the seismic response and lateral translation ${u}_{x}$ of the multistoried building along the x direction. Similarly, the second and third lines of Eq. ( 1.3 ) represent the traditional basic equation of motion utilized for obtaining the lateral translation ${u}_{y}$ along the y direction and torsional rotation about the vertical axis, respectively.

The calculated values of the parameters mentioned in Eq. (1) are displayed for the ‘L’-shaped building. Its orientation of frames about the center of gravity is delineated in Fig. 3 . Translation stiffness of each column is $\frac{12EI}{{l}^{3}}$ and is equal to $39.919\times {10}^{3} kN/m$ . It consists of 45 columns and hence translation stiffness of each story is equal to $1.796\times {10}^{6 } kN/m$ . ${k}_{xx}={k}_{yy}$ and is equal to $1.8\times {10}^{6}kN/m$ . ${k}_{yx}$ = ${k}_{xy}$ and is equal to 0. ${k}_{\theta x}$ equals to $-0.62\times {10}^{6}kN/m$ and ${k}_{\theta y}$ equals to $0.62\times {10}^{6}kN/m$ . ${k}_{\theta \theta }$ equals to $369.86\times {10}^{6}kN/m$ . The masses of floors and roof are 686 t and 366 t, respectively. The value of $\underline{y}=\underline{x}$ and is equal to $0.3392b$ .

Orientation of frames about center of gravity

4 Response spectrum analysis

Seismic response quantities like base shear, base moment, torsion, roof displacement, and rotation of the unsymmetrical buildings along with the square-shaped buildings of varying heights subjected to six main Indian ground accelerations have been calculated using response spectrum analysis [ 1 ]. The selected ground accelerations from Center for Engineering Strong Motion Data (CESMD) along the x as well as y directions are shown in Figs. 4 and 5 . The results were compared to that due to design response spectra given in IS 1893 (part 1):2016 [ 41 ]. First of all, structural properties of the building, mass as well as stiffness matrices, were defined. Eqs. ( 2 ) and ( 3 ) have respectively provided the mass and stiffness matrices of the ‘U’-shaped 5-story building, unsymmetrical about the y axis, subjected to ground motion along the y direction. Since the buildings considered are reinforced concrete structures, the damping ratio ( ${\zeta }_{n})$ of all the modes are taken as 5%. The selected earthquakes are Bhuj earthquake, Uttarkashi earthquake, Chamba earthquake, Chamoli earthquake, NE-INDIA earthquake (India Burma), and NE-INDIA earthquake, along with the IS 1893:2016 (rocky soil). For these earthquake ground motions, Prism software forms the elastic response spectrum. Table 3 presents the peak ground motions in the y direction.

Various ground accelerations in x direction

Various ground accelerations in y direction

The natural frequencies ${(\omega }_{n})$ and mode shapes ( ${\phi }_{n})$ of the Eigen value problem are determined by solving the characteristic equation utilizing MATLAB tool. The corresponding natural time periods are calculated using the relation ${T}_{n}=2\pi /{\omega }_{n}$ . It is followed by the computation of the peak response in the every ${n}^{th}$ mode, where n = 1, 2,…, N for the square-shaped building, and n = 1, 2,…, 2N for the ‘T’ and ‘U’-shaped buildings, and n = 1, 2,…, 3N for the ‘L’-shaped buildings. Spectral deformation $({D}_{n})$ and pseudo spectral acceleration ${(A}_{n})$ , corresponding to the natural time period ${T}_{n}$ and damping ratio ${\zeta }_{n}$ each mode is read out from each ground acceleration's deformation and acceleration response spectra. The lateral deformations and rotations of the floors due to each mode are computed employing Eqs. ( 4 ) and ( 5 ).

The equivalent static forces, which are lateral forces ${f}_{yn}$ and ${f}_{\theta n}$ , are calculated by Eqs. ( 6 ) and ( 7 ), respectively. Subsequently, the base shear ${(V}_{bn})$ , base moment ( ${M}_{bn})$ , and base torsion ( ${T}_{bn})$ are calculated by static analysis of the structural frame subjected to external forces ${f}_{yn}$ and ${f}_{\theta n}$ utilizing Eqs. ( 8 ), ( 9 ), and ( 10 ), respectively.

where, ${A}_{h}=\frac{{S}_{a}}{g}\frac{I}{R}\frac{Z}{2}$

where, ${M}_{n}^{*}$ is the effective modal mass of mode ‘n’ and ${h}_{n}^{*}$ is the effective modal height mode ‘n’. The complete quadratic combination (CQC) model combination rule was adopted, since the natural time periods of the modes are closely spaced. The total seismic response due to all the significant modes are calculated employing Eq. ( 11 ). Even though all the modes' contributions were considered in calculating the seismic responses, only the first few modes noticeably contributed.

where, ${\rho }_{in}=\frac{{\zeta }^{2}{\left(1+{\beta }_{in}\right)}^{2}}{{\left(1-{\beta }_{in}\right)}^{2}+4{\zeta }^{2}{\beta }_{in}}$

5 Pushover analysis

With pushover analysis, a type of nonlinear static analysis, a building’s seismic performance may be essentially determined by simply applying incremental lateral force until the structure collapses. The pushover curve is a crucial tool for determining damage limit states and obtaining seismic behavior. A pushover curve is plotting a deflection parameter dependent on strength. Based on the performance of the structure, a plot versus plastic rotation may be created to indicate the strength level attained in specific members to the lateral displacement at the top of the structure or bending moment. Pushover study findings provide the load level, deflection ductile capacity, and structural system mechanism for failure. An element (or group of elements) reaching a lateral deformation level at which significant strength degradation begins then performance level can be measured, as illustrated in Fig. 6 .

Performance level

6 Results and discussion

The results based on base shear, base torsion, base moment, story displacement, inter-story drift, roof displacement, and roof rotation of buildings of unsymmetrical plan are discussed along with building of symmetrical plan. The center of the mass and stiffness matrices do not coincide with the center of gravity of buildings due to irregular planning.

6.1 Fundamental natural time period and mode shapes

Regarding the square-shaped building, its plan is symmetrical about both axes, therefore, the equation of motion, i.e., Eq. (1) can be detached in both the x and y axes. Moreover, torsional effects will not be there. These leads an ‘N’-story square-shaped building to have ‘N’ DOF. Meanwhile, the ‘T’ and ‘U’-shaped buildings are symmetrical about the x axis and unsymmetrical about the y axis. While uncoupled equation can be made along the x direction, both lateral translations along the y axis and torsional moment are coupled in the y direction. Therefore, DOF along the y direction will be 2N for an ‘N’-story ‘T’ as well as ‘U’-shaped building. Interestingly, the ‘L’-shaped building is unsymmetrical about both the x and y directions, consequently, the lateral translation along the x and y directions and torsional moment are coupled along both the x and y directions. Therefore, DOF of an ‘N’-story ‘L’-shaped building will be 3N in both the x and y directions. For example, DOF of the 5-story ‘U’ and ‘L’-shaped buildings are 10 and 15, respectively. Their characteristic equation is solved using MATLAB to get the natural frequencies and mode shapes after the formation of corresponding mass and stiffness matrices. Mass and stiffness matrices of the ‘U’-shaped building are provided in Eqs. ( 2 ) and ( 3 ). Table 4 presents natural time periods of all the buildings subjected to ground excitation along the y direction. It shows that when the number of stories of any building increases, natural time period gradually increases. For example, fundamental natural time periods of the 5th, 8th, 10th, and 12th stories of the ‘T’-shaped building are 0.395 sec, 0.629 sec, 0.786 sec, and 0.948 sec, respectively. While the ‘L’-shaped building demonstrates lowest fundamental natural time periods among all the buildings, it is the ‘U’-shaped building exhibiting highest fundamental natural time periods. Except the first few modes, remaining modes of all the buildings mark their corresponding natural time periods are highly closed. As a conclusion, the modal combination rule, CQC, is used instead of square root of summation of squares for calculating the total seismic responses from the individual modal responses.

6.2 Spectral acceleration and spectral displacement

PRISM software constructed the response spectrum for all the above ground accelerations. The spectral acceleration coefficient was obtained from the above response spectrum for a particular value of natural time period and damping ratio, in addition to the elastic response spectrum from IS 1893 (part 1):2016. The acceleration spectrum decreases as natural time period lengthens, and the displacement spectrum increases proportionally to natural time period. For example, natural time periods of the five modes of the 5-story square building are 0.416 sec, 0.143 sec, 0.092 sec, 0.073 sec, and 0.065 sec. The corresponding values of spectral displacement are 7.564 mm, 1.013 mm, 0.370 mm, 0.235 mm, and 0.197 mm, respectively, and spectral accelerations are 0.173 g, 0.208 g, 0.177 g, 0.179 g, and 0.188 g, respectively. This indicates that spectral displacement is varying directly proportional to natural time period and vice versa to spectral acceleration. Acceleration as well as displacement response spectra for the various ground accelerations in the x and y directions are depicted in Fig. 7 a and b. Spectral acceleration response spectra for various ground acceleration have been matched with response spectra for rocky soil from IS 1893:2016, as shown in Fig. 7 .

Response spectra from IS 1893:2016 (rocky soil)

6.3 Base shear

Base shear is an estimate of maximum expected lateral force that will occur due to seismic ground motion at the base of the structure. Base shear is affected by the unsymmetrical plan of the building, in addition to weight of the structure and ground acceleration. The total seismic response of base shear is obtained by multiplying both dynamic and static responses. Static response is proportional to seismic weight of the building and dynamic response is nothing but the spectral acceleration (Sa/g) from the response spectrum of each ground acceleration. Seismic weights of the 5, 6, 7, and 8-story buildings are respectively equal to 6042 kN, 9918 kN, 12502 kN, and 15086 kN, irrespective of the shape of the buildings. Static response is linearly increasing from 5 to 12 stories of a particular building. For example, model static responses of the 5-story square building subjected to Bhuj ground acceleration are 5336.726 kN, 520.090 kN, 138.621 kN, 39.506 kN, and 7.125 kN, respectively, and dynamic responses, i.e., design horizontal acceleration seismic coefficients, are 0.091, 0.110, 0.094, 0.095, and 0.100, respectively. Design horizontal acceleration seismic coefficient ( ${A}_{n})$ is obtained from spectral acceleration $\left(\frac{{S}_{a}}{g}\right)$ , in which, the values of the zone factor (Z), importance factor (I), and response reduction factor (R) are taken as 0.36, 1.5, and 5, respectively. After multiplying these two responses, base shears are achieved for the five individual modes as 487.982 kN, 57.298 kN, 12.962 kN, 3.736 kN, and 0.709 kN. Total base shear is calculated using the CQC modal combination rule and is equal to 492.319. Total base shears of other 5-story buildings are delineated in Table 5 , and the comparison of base shears of all the buildings having different stories are displayed in Fig. 8 . In all different-story buildings, the square-shaped building is giving maximum base shear when compared to other shaped buildings. Base shears of the 5th, 8th, 10th, and 12th stories of the square-shaped buildings subjected to Bhuj ground acceleration are respectively 8.15%, 8.55%, 11.85%, and 9.11% of seismic weight. From the 5th story to 10th story, base shear increases, however, it decreases toward the 12th story. Even though the static response of the 12-story square-shaped building is maximum, its dynamic response, i.e., spectral acceleration, of the first two modes is significantly less than that of a 10-story building. This is the reason behind the reduced base shear of the 12-story building; the same issue is valid for remaining buildings of different shapes. After the square-shaped building, it is the ‘U’-shaped building providing maximum base shear almost in all the story levels. Even though the ‘L’-shaped building is unsymmetrical about both axes, it demonstrates less value of base shear, and base shears of both the ‘L’ and ‘T’-shaped buildings are tantamount approximately. As far as modal contribution is concerned, the first mode contributes nearly 99% of total response for the ‘U’, ‘T’, and square-shaped buildings, and it is the first two modes giving the same amount for the ‘L’-shaped building.

Gopeshwar ground motion provided higher base shear than Bhatwari, Bhuj, and Bokajan ground motions. Fig. 8 illustrates that Chamba and Ummulong ground motions provide less seismic response than the one given as per IS 1893:2016. On comparing the overall performance, it is Gopeshwar’s ground motion exhibiting maximum base shear in the 10-story square-shaped building, which is equal to 3590.041 kN. It is 28.716% of seismic weight. Fig. 8 indicates that there is no considerable increment in base shear based on increment in the number of stories due to certain ground motion, such as Bokajan, Ummulong, and IS code. The reason is that the increased static response is balanced by reduced dynamic response, mainly due to highly randomly distributed spectral acceleration, which depends on natural time period for a fixed damping ratio. Therefore, it is determined that square building is highly vulnerable among all the considered and out of the unsymmetrical buildings. It is the ‘U’-shaped building highly susceptible to earthquake for the 5th and 8th stories, and almost all the unsymmetrical buildings perform well for the 10th and 12th stories. It is also depicted that the ‘L’, ‘T’, and ‘U’-shaped buildings are alternatively sensitive for varying earthquakes. Base shear in the ‘L’, ‘T’ and ‘U’-shaped buildings decreases by 30%, unlike the square-shaped building where base shear decreases by 40%.

Base shears for ground accelerations in y direction

6.4 Base moment

Base moment of each mode is obtained by multiplying the corresponding base shear with its center of gravity distance from the structure base. The variation of base moment of all models is almost very similar to that of base shear as these two are linearly proportional. Base moment of almost all the buildings due to Gopeshwar ground motion attains highest value among all the considered ground accelerations. IS 1893:2016 and Ummulong give least value. The 10-story square-shaped rectangular building subjected to Gopeshwar ground motion attains highest value of base moment and is equal to 81165.200 kN.m. Almost same value of base moment, i.e., 81005.653 kN.m, was attained in the same shaped building of 12-story subjected to same ground acceleration. The variations of base moments for ground accelerations in the y direction are presented in Fig. 9 .

Base moments for ground accelerations in y direction

6.5 Base torsion

Earthquake induces torsion in building due to the eccentricity of masses and stiffness, in addition to the unsymmetrical plan. Accidental torsion is typically used to describe the torsional motion of buildings with ostensibly symmetrical plans, such as the square building. A small portion of the structure's overall seismic forces are produced by this motion. Unintentional torsion provided around 4% of the overall force for the structure and earthquake under consideration, while other buildings' seismic responses have marked bigger contributions. Because (1) the rotational base motion is not defined and (2) it is impractical to identify and analyze the impact of each source of asymmetry in a building with a nominally symmetrical plan, the structural response associated with accidental torsion cannot be calculated in structural design. For this reason, in this research, the square buildings are considered free of torsion, as indicated in Table 5 . Figure 10 shows variation of base torsions based on the type of buildings, ground accelerations, and number of stories. Gopeshwar ground acceleration provides highest value of base torsion, comparing all the ground accelerations. Base torsion was calculated according to IS 1893:2016, and Ummulong gives the least value. The ‘U’-shaped building having 12 stories subjected to Gopeshwar ground acceleration provides high value of base torsion, and the value is equal to 6971.374 kN.m. The ‘T’-shaped building displays less torsion among unsymmetrical buildings. The 5th, 8th, 10th, and 12th stories of the ‘U’-shaped buildings subjected to Gopeshwar ground acceleration provide base torsions of 6096.483 kN.m, 7907.421 kN.m, 7700.633 kN.m, and 6971.374 kN.m, respectively. It clearly points out that base torsion increases as the number of stories increases from 5 to 8, while it then decreases from 8 to 12 stories. Therefore, it attains the second maximum torsion value at the 5-story building. It is mainly due to the lower dynamic response in the 10 and 12-story buildings owing to the reduced spectral accelerations corresponding to the natural time periods. The base torsions of the ‘T’ and ‘L’-shaped buildings are 65% to 70% less than that of the U-shaped building. The results obtained from Khanal and Chaulagain [ 4 ] state that the torsional irregularity increases as the plan irregularity increases. In the present study, base torsions in the ‘U’-shaped building are 70% to 75% greater than those in the ‘T’ and ‘L’-shaped buildings.

Base torsions of various unsymmetrical buildings of different stories

6.6 Inter-story drift

The story drifts in any story subjected to a horizontal design force should not exceed 0.004 times the height of the story, as mentioned in IS 1893:2016 (part 1). The permissible drift ratio is 0.004 (100%) and it is clear that from the first floor to the fourth floor, the inter-story drift values are more than 0.004. This demonstrates that it exceeds the permissible limit. As the first floor displays the maximum drift ratio, it has been compared in all the 12-story buildings subjected to Gopeshwar ground acceleration. The inter-story drift ratios in the ‘L’, ‘T’, ‘U’, and square-shaped buildings are 153.62%, 153.77%, 211.52%, and 151.6%, respectively. Figure 11 displays that the irregular building provides 50% to 110% more inter-story drift than the permissible limit mentioned by IS 1893:2016. While comparing the results obtained from Khanal and Chaulagain [ 4 ], it is clear that the inter-story drifts in irregular buildings are 30% more than that in the reference model.

Inter-story drifts of unsymmetrical multi-story buildings of different stories

6.7 Roof rotation

In all the irregular buildings, the maximum roof rotation is due to Gopeshwar ground acceleration among the considered ground accelerations. In the 5-story building, Bhatwari ground acceleration leads to other ground accelerations, inducing maximum roof rotation in all the irregular buildings. While considering Gopeshwar ground acceleration in the 12-story buildings, roof rotations for the ‘L’, ‘T’, and ‘U’-shaped buildings are 1.322 rad, 1.470 rad, and 1.871 rad, respectively. Since the square-shaped building is symmetrical about both the x and y axes, it will not induce any rotation. Different ground accelerations, mainly Gopeshwar, Bhuj, along with Bhatwari, induce maximum roof rotations in the 5, 8, 10 and 12-story buildings. It is owing to the high randomly distributed spectral acceleration against the natural time period for different ground accelerations.

While comparing roof rotations among all the 5, 8, 10, and 12-story buildings, the ‘U’-shaped building provides 30% to 70% maximum rotation than the ‘L’ and ‘T’-shaped buildings, and the ‘L’-shaped building has the least roof rotation. Comparing the results obtained from Khanal and Chaulagain, [ 4 ], it is revealed that roof rotation in irregular buildings increases 12% more than the reference models. In this study, roof rotations in the ‘U’-shaped building are 30% to 70% greater than those in the ‘L’ and ‘T’-shaped buildings, as depicted in Fig. 12 .

Story drift in $\theta$ direction

6.8 Roof displacement

Roof displacement increases linearly based on the increment of the number of stories of all types of the buildings subjected to all the considered ground accelerations. The ‘U’-shaped buildings attain maximum roof displacement among all the buildings. Meanwhile, roof displacements in the ‘L’ and ‘T’-shaped building are lower than those in the reference building; the square-shaped building is taken as the reference building. The maximum roof displacements at the 12-story square, ‘L’, ‘T’, and ‘U’-shaped buildings due to Gopeshwar ground motion are 134.045 mm, 133.341 mm, 134.089 mm, and 164.801 mm, respectively.

The ‘T’-shaped building yielded 13% less roof displacement than the square buildings. Thus, the ‘T’-shaped buildings lie within safer side when compared to other buildings. Meanwhile, the ‘U’-shaped building displays 50% to 100% more roof displacement than the square-shaped building, hence, it is vulnerable to all other buildings. Comparing the results obtained from Khanal and Chaulagain, [ 4 ], it is found that roof displacements in irregular buildings are 20% more than that in the reference model. In this study, roof displacement in the ‘U’-shaped building is 50% to 100% greater than the square-shaped buildings, as shown in Fig. 13 for different ground motions.

Roof displacements of various buildings for ground accelerations in y direction

6.9 Performance level

ATC40 [ 44 ] guideline was studied before conducting the pushover analysis on the selected multi-story buildings using ETABS software. The pushover analysis results have been checked to ensure that the nonlinearity is accurately captured. It is possible that the current results appear lightly beyond elastic due to conservative modeling assumptions or an underestimation of plastic hinge properties. In addition, fixation of target displacement as 0.8% of total height of the building, i.e., pushover analysis was not extended until the collapse of the building. But performance points were achieved for all types of the buildings except the ‘L’-shaped 5-story and ‘U’-shaped 12-story buildings. All the buildings crossed the elastic status. The attainment of the performance point for the ‘U’-shaped 10-story building from ETABS software is depicted in Fig. 14 .

Performance point for ‘U’-shaped 10-story building

The location of hinges in various stages can be obtained from pushover curve. The range AB is elastic range, B to IO is the range of IO, IO to LS is the range of LS, and LS to CP is the range of CP mentioned by ATC 40. If all the hinges are within the CP limit, then the structure is said to be safe. However, depending upon the importance of structure, the hinges after the IO range may also need to be retrofitted. Here, when comparing the performance point of all buildings, the ‘U’-shaped buildings perform to the maximum shear force. Ruggieri and Uva [ 40 ] highlighted the significant impact that the choice of control node can have on the pushover analysis results. The conventional choice is to place the control node at the center of mass of the last story, but this can lead to non-conservative results, particularly for buildings with in-plan irregularities.

On comparing the performance level, base shears in the 10-story buildings such as the square, ‘L’, ‘T’ and ‘U’-shaped buildings are 100%, 47.21%, 47%, and 65.38%, respectively, i.e., base shear of the square-shaped building is taken as 100 % after assuming it as the reference one. The above discussion indicated that the ‘U’-shaped building has 20% to 25% more performance than the ‘L’ and ‘T’-shaped buildings. The performance of symmetrical building is better than unsymmetrical building. The ‘L’-shaped building with 5 stories and ‘U’-shaped building with 12 stories do not reach their performance points. While comparing the results of Palagala and Singhal [ 3 ] with the current study, the performance of infilled reinforced concrete frame increases the seismic performance level than bare-framed buildings. Dalal and Dalal [ 6 ] suggested that PBPD-IO does not achieve its performance level whereas in this study the ‘L’-5 and ‘U’-12-story buildings do not achieve their performance levels. Dalal and Dalal [ 6 ] reported that the FBD frame is found to be vulnerable to damage whereas in this study, the ‘L’-shaped buildings are highly vulnerable. Hareen and Mohan [ 7 ] discussed that while considering the ‘L’, ‘T’ and ‘U’-shaped buildings, performance points are obtained at peak ground accelerations of 0.16 g, 0.24 g, and 0.36 g, respectively. In this study, for the 10-story buildings of the ‘L’, ‘T’ and ‘U’-shaped plans, the performance points are achieved at peak ground accelerations of 0.585 g, 0.582 g, and 0.572 g, respectively, as listed in Table 6 . Figure 15 illustrates the capacity curves for the 5, 8, 10 and 12-story buildings.

Capacity curves for various multi-story buildings

Based on the plastic hinge formation status, it is found that the ‘L’-8 story, ‘T’-8 story, and ‘T’-12 story buildings perform well, as their performance lies within LS in the nonlinear static analysis. The nonlinear performance of the buildings is presented in Table 6 .

7 Conclusions

This article presented and discussed the seismic performance of different unsymmetrical buildings such as ‘L’, ‘T’, and ‘U’-shapes along with square-shaped buildings with varying stories, i.e., 5, 8, 10, and 12 stories. Initially, 6 ground accelerations of various earthquakes from zone V and IS 1893:2016 (rocky soil) data were selected to frame an elastic response spectrum utilizing PRISM software. Response spectrum analysis was carried out for all the buildings to calculate base shear, base moment, base torsion, roof displacement, roof rotation, and story drift. Seismic response of all the buildings was investigated. The following conclusions can be made:

Even though the square-shaped buildings are symmetrical about both axes, their seismic responses such as base shear and base moment, are greater than those of unsymmetrical plan buildings, such as the ‘L’ and ‘T’-shaped buildings, because seismic weights of the square-shaped buildings are approximately twice those of the ‘L’ and ‘T’-shaped buildings. Total story drift response exceeds the allowable limit as per IS 1893:2016 (part 1) for all types of the buildings, and it reaches the maximum value for the ‘U’-shaped building. It is around 110% higher for the ‘U’-shaped building and 50% for all other buildings. Regarding roof displacement, the ‘U’-shaped building of 12 stories attains maximum value of 165 mm. Therefore, concerned with the shape of the irregular buildings, the ‘U’-shaped building is more vulnerable than all other irregular buildings.

The seismic responses given by the x component ground accelerations are less than those by the y component ground accelerations. This is the case for all the buildings, except the square-shaped building which is unsymmetrical about the y axis. On comparing the ground accelerations, Gopeshwar ground acceleration provides maximum seismic responses compared to any other ground accelerations because natural time periods of the first few models of all the buildings are located in the acceleration-sensitive region of this ground acceleration.

It is known from the nonlinear static analysis that all the 12-story buildings achieve the hinge status of greater than CP, and this hinge state occurs in maximum number of the ‘U’ and ‘L’-shaped buildings, followed by the ‘T’-shaped building. It delineates that the ‘U’-shaped building is highly susceptible to earthquakes.

Even though the static response of the 12-story square-shaped building is maximum, its dynamic response, i.e., spectral acceleration, of the first two modes is considerably less when compared to that of a 10-story building. As a result of high randomly distributed spectra acceleration, the increased static response is balanced by the reduced dynamic response. Therefore, base shears as well as base moments of some buildings of 12-story, mainly the square-shaped building, are less than those of the same buildings of 10-story.

Fundamental natural time periods gradually increase when the number of story increases from 5 to 12 for all the buildings. Fundamental natural time periods of the 12-story ‘U’-shaped building is maximum among all the buildings and is equal to 1.233 sec. Therefore, it is concluded that the shape and the number of stories of the buildings influence natural time periods which, in turn, affect their spectral accelerations.

Base torsions in the ‘T’ and ‘L’-shaped buildings are 65% to 70% less than that in the ‘U’-shaped building. Due to the less amount of dynamic response in the 10 and 12-story buildings beacuse of the reduced spectral accelerations corresponding to the natural time periods, base torsions of all the unsymmetrical buildings decrease from 8 to 12 stories.

Data availability

The authors declare that the data supporting the findings of this study are available within the article.

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Department of Civil Engineering, St. Xavier’s Catholic College of Engineering, Nagercoil, Tamil Nadu, 641062, India

Antony Vimal Paul Pandian

Departamento de Ciencias de La Construcción, Facultad de Ciencias de La Construcción Ordenamiento Territorial, Universidad Tecnológica Metropolitana, Dieciocho 161, Santiago, Chile

Krishna Prakash Arunachalam & Siva Avudaiappan

Department of Building Engineering, Energy Systems and Sustainability Science, Faculty of Engineering and Sustainable Development, University of Gävle, 801 76, Gävle, Sweden

Alireza Bahrami

Department of Civil Engineering, Universidad César Vallejo, Lima, Peru

Lenin Miguel Bendezu Romero

Department of Civil Engineering, Prince Mohammad Bin Fahd University, Dhahran, 34754, Saudi Arabia

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Antony Vimal Paul Pandian-Conceptualization, methodology, investigation, software, data curation, validation, formal analysis, visualization, writing—original draft preparation, writing—review and editing. Krishna Prakash Arunachalam-Conceptualization, methodology, investigation, software, data curation, validation, formal analysis, visualization, writing—original draft preparation, writing—review and editing. Alireza Bahrami-Conceptualization, methodology, investigation, software, data curation, validation, formal analysis, visualization, writing—original draft preparation, writing—review and editing. Lenin Miguel Bendezu Romero-Methodology, investigation, software, data curation, validation, formal analysis, writing—original draft preparation, writing—review and editing. Siva Avudaiappan-Conceptualization, investigation, software, data curation, validation, formal analysis, writing—original draft preparation, writing—review and editing. Paul O. Awoyera-Conceptualization, methodology, validation, formal analysis, writing—original draft preparation, writing—review and editing.

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Pandian, A.V.P., Arunachalam, K.P., Bahrami, A. et al. Unsymmetricity effects on seismic performance of multi-story buildings. Discov Appl Sci 6 , 476 (2024). https://doi.org/10.1007/s42452-024-06099-3

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Report on the 2010 Chilean earthquake and tsunami response
In July 2010, in an effort to reduce future catastrophic natural disaster losses for California, the American Red Cross coordinated and sent a delegation of 20 multidisciplinary experts on earthquake response and recovery to Chile. The primary goal was to understand how the Chilean society and relevant organizations responded to the magnitude 8.8 Maule earthquake that struck the region on February
Case study: Chile (2010) and Nepal (2015) Earthquake
Chile: Primary Effects. •Occured on the coast. •Magnitude was 8.8. •5th largest earthquake ever to be recorded by a seismograph. •500 people lost their lives and 12,000 injured and 800,000 poeole affected. •GDP in 2010 (12681.77) •56 hospitals, 220,000 houses, 4,500 schools, 53 ports. •Lost power, water supplies and communications ...
Nepal Earthquake 2015
A map to show the location of Nepal in Asia. At 11.26 am on Saturday, 25th of April 2015, a magnitude 7.9 earthquake struck Nepal. The focus was only eight kilometres deep, and the epicentre was just 60 kilometres northwest of Kathmandu, the capital city of Nepal. At the time of the earthquake, Kathmandu had 800,000+ inhabitants.
AQA Geography GCSE Lessons
Primary effects; Secondary effects; Immediate response; Long-term response; ... is a natural hazard * Global distribution of plate boundaries * Physical processes at plate boundaries * Chile & Nepal earthquake case studies * Chile & Nepal Earthquake comparing earthquakes * Reducing the risk of tectonic activity * Living near a volcano This ...
Case study
Start studying Case study - Chile Earthquake. Learn vocabulary, terms, and more with flashcards, games, and other study tools. ... (Primary effect) 4,500 schools. How many schools were destroyed? ... (Airport) Much of Chile lost power. Other primary effects? (Power) 1500km. How many km of roads were destroyed? (Secondary effects) Evacuation ...
Unsymmetricity effects on seismic performance of multi-story buildings
The unsymmetrical configurations in buildings lead to non-uniform distributions in their strength, mass, and stiffness, and they are consequently prone to damage during seismic hazards. In this study, the seismic performance of multi-story buildings with 5, 8, 10, and 12 stories of square, 'L', 'T', and 'U'-shaped buildings have been investigated. The research deals with the ...
Chile vs Nepal Case study- primary and secondary effects of ...
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Case Study: CHILE EARTHQUAKE Flashcards
Study with Quizlet and memorize flashcards containing terms like (Primary effects) How many homes were destroyed?, (Primary effects) How many schools were destroyed?, (Primary effects) How many ports were destroyed? and more.