Seismic risk or earthquake risk is the potential impact on the built environment and on people's well-being due to future earthquakes. Seismic risk has been defined, for most management purposes, as the potential economic, social and environmental consequences of hazardous events that may occur in a specified period of time. A building located in a region of high seismic hazard is at lower risk if it is built to sound seismic engineering principles. On the other hand, a building located in a region with a history of minor seismicity, in a brick building located on fill subject to liquefaction can be as high or higher risk.
Peak ground acceleration (PGA) is equal to the maximum ground acceleration that occurred during earthquake shaking at a location. PGA is equal to the amplitude of the largest absolute acceleration recorded on an accelerogram at a site during a particular earthquake. Earthquake shaking generally occurs in all three directions. Therefore, PGA is often split into the horizontal and vertical components. Horizontal PGAs are generally larger than those in the vertical direction but this is not always true, especially close to large earthquakes. PGA is an important parameter for earthquake engineering, The design basis earthquake ground motion (DBEGM) is often defined in terms of PGA.
Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on structures and with recent experiences with large earthquakes near urban centers, the need of seismic retrofitting is well acknowledged. Prior to the introduction of modern seismic codes in the late 1960s for developed countries and late 1970s for many other parts of the world, many structures were designed without adequate detailing and reinforcement for seismic protection. In view of the imminent problem, various research work has been carried out. State-of-the-art technical guidelines for seismic assessment, retrofit and rehabilitation have been published around the world – such as the ASCE-SEI 41 and the New Zealand Society for Earthquake Engineering (NZSEE)'s guidelines. These codes must be regularly updated; the 1994 Northridge earthquake brought to light the brittleness of welded steel frames, for example.
Seismic analysis is a subset of structural analysis and is the calculation of the response of a building structure to earthquakes. It is part of the process of structural design, earthquake engineering or structural assessment and retrofit in regions where earthquakes are prevalent.
Earthquake engineering is an interdisciplinary branch of engineering that designs and analyzes structures, such as buildings and bridges, with earthquakes in mind. Its overall goal is to make such structures more resistant to earthquakes. An earthquake engineer aims to construct structures that will not be damaged in minor shaking and will avoid serious damage or collapse in a major earthquake. A properly engineered structure does not necessarily have to be extremely strong or expensive. It has to be properly designed to withstand the seismic effects while sustaining an acceptable level of damage.
Seismic base isolation, also known as base isolation, or base isolation system, is one of the most popular means of protecting a structure against earthquake forces. It is a collection of structural elements which should substantially decouple a superstructure from its substructure that is in turn resting on the shaking ground, thus protecting a building or non-building structure's integrity.
National Center for Research on Earthquake Engineering is an organisation in Da'an District, Taipei, Taiwan.
Nabih Youssef, S.E., F.A.S.C.E was an American structural engineer, most recognized for his work in seismic engineering.Youssef is recognized for translating academic structural engineering concepts into practical applications, most notably through the base isolation technique employed in the Los Angeles City Hall renovations. His significant achievements also include advancements in Performance-based building design and the use of a Steel plate shear wall in areas of high seismic risk.
A soft story building is a multi-story building in which one or more floors have windows, wide doors, large unobstructed commercial spaces, or other openings in places where a shear wall would normally be required for stability as a matter of earthquake engineering design. A typical soft story building is an apartment building of three or more stories located over a ground level with large openings, such as a parking garage or series of retail businesses with large windows.
An unreinforced masonry building is a type of building where load bearing walls, non-load bearing walls or other structures, such as chimneys, are made of brick, cinderblock, tiles, adobe or other masonry material that is not braced by reinforcing material, such as rebar in a concrete or cinderblock. The term is used in earthquake engineering as a classification of certain structures for earthquake safety purposes, and is subject to minor variation from place to place.
Earthquake-resistant or aseismic structures are designed to protect buildings to some or greater extent from earthquakes. While no structure can be entirely impervious to earthquake damage, the goal of earthquake engineering is to erect structures that fare better during seismic activity than their conventional counterparts. According to building codes, earthquake-resistant structures are intended to withstand the largest earthquake of a certain probability that is likely to occur at their location. This means the loss of life should be minimized by preventing collapse of the buildings for rare earthquakes while the loss of the functionality should be limited for more frequent ones.
The Earthquake Engineering Research Institute (EERI) is a leading technical society in dissemination of earthquake risk and earthquake engineering research both in the U.S. and globally. EERI members include researchers, geologists, geotechnical engineers, educators, government officials, and building code regulators. Their mission, as stated in their 5-year plan published in 2006, has three points: "Advancing the science and practice of earthquake engineering; Improving understanding of the impact of earthquakes on the physical, social, economic, political, and cultural environment; and Advocating comprehensive and realistic measures for reducing the harmful effects of earthquakes".
The following is a summary of significant earthquakes during the 21st century. In terms of fatalities, the 2004 Indian Ocean earthquake was the most destructive event with 227,898 confirmed fatalities, followed by the 2010 Haiti earthquake with about 160,000 fatalities, the 2008 Sichuan earthquake with 87,587 fatalities, the 2005 Kashmir earthquake suffered by Pakistan with 87,351 fatalities, and the 2023 Turkey–Syria earthquakes with at least 59,488 fatalities.
The Van Norman Dams, also known as the San Fernando Dams, were the terminus of the Los Angeles Aqueduct, supplying about 80 percent of Los Angeles' water, until they were damaged in the 1971 San Fernando earthquake and were subsequently decommissioned due to the inherent instability of the site and their location directly above heavily populated areas.
The National Society for Earthquake Technology – Nepal (NSET) is a Nepali non-governmental organization working on reducing earthquake risk and increasing earthquake preparedness in Nepal as well as other earthquake-prone countries.
Miyamoto International is a global structural engineering and disaster management firm best known for its work in California earthquake design for new and existing buildings as well as in the reconstruction of Port-au-Prince, Haiti and Christchurch, New Zealand following earthquakes in 2010 and 2011. Based in West Sacramento, California, the company has 25 offices in 12 countries worldwide.
Medhat Haroun was an Egyptian-American expert on earthquake engineering. He wrote more than 300 technical papers and received the Charles Martin Duke Lifeline Earthquake Engineering Award (2006) and the Walter Huber Civil Engineering Research Prize (1992) from the American Society of Civil Engineers.
Andrew Stuart Whittaker is an American structural engineer who is currently a SUNY Distinguished Professor in the Department of Civil, Structural and Environmental Engineering at the University at Buffalo, State University of New York.
Jack Moehle is the Ed and Diane Wilson Presidential Professor of Structural Engineering at the University of California, Berkeley.
Gilbert Arthur Hegemier is an American engineer and academic known for his work in structural and aerospace engineering, as well as applied physics. He is a Distinguished Professor Emeritus at the Jacobs School of Engineering at the University of California, San Diego (UCSD), and is recognized as one of the founding faculty members of the institution. Hegemier's research has focused on enhancing public safety through the development of retrofitting techniques for structures in earthquake-prone areas, as well as on protective technologies against blast and ballistic threats. His contributions have been acknowledged by his involvement with professional organizations such as the American Institute of Aeronautics and Astronautics, the Earthquake Engineering Research Institute, and the American Society of Mechanical Engineers, where he has been a fellow since 1997.
