 | The examples and perspective in this article may not represent a worldwide view of the subject.(December 2010) |
Urban seismic risk is the risk of earthquakes damaging or destroying people and things in towns and cities. [1] Even if a big earthquake is likely urban seismic risk can be minimized with good earthquake construction, and seismic analysis. One of the best ways to deal with the issue is through an earthquake scenario analysis. Earthquake engineering can reduce the risk.
The IDNDR secretariat launched the RADIUS (risk assessment tools for diagnosis of urban areas against seismic disasters) initiative in 1996 to promote worldwide activities for the reduction of urban seismic risk, which experienced rapid growth particularly in developing countries, by helping to raise public awareness. [2]
One of the disaster risk reduction themes set forth by the United Nations International Strategy for Disaster Reduction project PreventionWeb, is urban risk and planning. This theme refers to the measurement and management of urban hazards and vulnerability in order to improve awareness and local capacity to effectively reduce disaster risk. [3]
In earthquake-prone areas, all buildings built to 20th century standards may be dangerous, [4] but shortly after the 1999 İzmit earthquake, which killed over 17 thousand people, a new seismic code was brought into force to protect against earthquakes in Turkey. [5] [6] Also following that earthquake a so-called earthquake tax was raised during the government of Bülent Ecevit. [7] Initially thought as a temporary tax, it became permanent. [5] In 2007 the seismic code was strengthened. [8] [9] However, it is alleged that builders often ignored the rules due to corruption. [10] After the 2011 Van earthquakes Prime Minister Recep Tayyip Erdoğan said: "Municipalities, constructors and supervisors should now see that their negligence amounts to murder." [11] In 2018, a zoning law gave amnesties to some unlicensed buildings and some with unlicensed floors. [11]
Further resilience over the 2007 code was mandated in the 2018 Turkish Seismic Code, which took effect on 1 January 2019. [8] [12] Improvements included design supervision and site specific hazard definitions, [13] and for new buildings in vulnerable regions required rebar in high quality concrete. [14] Beams and columns in those buildings must be in the right place to properly absorb shaking. [14] The code is said by foreign experts to be very modern and similar to US codes. [15] However, these 21st century building codes were not very well enforced. [4]
In a bid to shore up support going into the 2018 Turkish presidential election, the government offered amnesties for violations of the building code, allowing non-compliance to continue with the payment of a fee. [16] This poor enforcement of seismic codes was a contributing factor to the devastation of the 2023 Turkey–Syria earthquakes in which over 42,000 people died in Turkey. [6] There were high incidences of support column failure leading to pancake collapses, which complicated rescue efforts. Experts lamented the practice would turn cities into graveyards. [17] The 2023 Turkey–Syria earthquakes collapsed many older buildings and some recent ones: [18] the Environment and Urbanization Ministry is assessing the damage. [19]
Unreinforced masonry buildings are vulnerable. [20] Many older buildings in Istanbul are vulnerable to pancake collapses. [21] Retrofitting old buildings is possible but expensive. [21] Although over 3 million housing units nationwide were strengthened in the 2 decades before 2023, as of that year many apartment blocks do not meet 21st century standards. [18] Building with wood has been suggested. [22]
Cities are a mixture of old and new construction as in this picture. Note the old brick building mixed in with the new highrises, and the famous Toronto CN Tower. Similar to methodologies used in nuclear reactors, [23] a seismic walkdown of the city is the best way to identify vulnerabilities and possible places for improvement.
Toronto is located on the shores of Lake Ontario, the site of much microseismicity. [24] Toronto was struck by a 5.0 magnitude earthquake on June 23, 2010, [25] and a 5.1 magnitude earthquake on May 17, 2013. [26]
There are many places where the risk of seismic damage to older buildings is quite high. Old brick buildings on poor soils are highly vulnerable to earthquake damage, particularly when the mortar holding the bricks together has decayed. Problems increase if there is the possibility for soil or soil liquefaction.[ citation needed ]
Even in buildings which are capable of withstanding an earthquake without structural failure there may be risk to people due to interior hazards. Items such as suspended ceilings and light fixtures have almost no seismic ruggedness. Warehouse stores where heavy merchandise is stacked are a particular hazard.[ citation needed ]
A disaster is an event that causes serious harm to people, buildings, economies, or the environment, and the affected community cannot handle it alone. Natural disasters like avalanches, floods, earthquakes, and wildfires are caused by natural hazards. Human-made disasters like oil spills, terrorist attacks and power outages are caused by people. Nowadays, it is hard to separate natural and human-made disasters because human actions can make natural disasters worse. Climate change also affects how often disasters due to extreme weather hazards happen.
A natural disaster is the very harmful impact on a society or community after a natural hazard event. Some examples of natural hazard events include avalanches, droughts, earthquakes, floods, heat waves, landslides, tropical cyclones, volcanic activity and wildfires. Additional natural hazards include blizzards, dust storms, firestorms, hails, ice storms, sinkholes, thunderstorms, tornadoes and tsunamis. A natural disaster can cause loss of life or damage property. It typically causes economic damage. How bad the damage is depends on how well people are prepared for disasters and how strong the buildings, roads, and other structures are. Scholars have been saying that the term natural disaster is unsuitable and should be abandoned. Instead, the simpler term disaster could be used. At the same time the type of hazard would be specified. A disaster happens when a natural or human-made hazard impacts a vulnerable community. It results from the combination of the hazard and the exposure of a vulnerable society.
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.
Earthquake insurance is a form of property insurance that pays the policyholder in the event of an earthquake that causes damage to the property. Most ordinary homeowners insurance policies do not cover earthquake damage.
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.
Induced seismicity is typically earthquakes and tremors that are caused by human activity that alters the stresses and strains on Earth's crust. Most induced seismicity is of a low magnitude. A few sites regularly have larger quakes, such as The Geysers geothermal plant in California which averaged two M4 events and 15 M3 events every year from 2004 to 2009. The Human-Induced Earthquake Database (HiQuake) documents all reported cases of induced seismicity proposed on scientific grounds and is the most complete compilation of its kind.
The architecture of Turkey includes heritage from the ancient era of Anatolia to the present day. Significant remains from the Greco-Roman period are located throughout the country. The Byzantine period produced, among other monuments, the celebrated Hagia Sophia in Constantinople. Following the arrival of the Seljuk Turks in the 11th century, Seljuk architecture mixed Islamic architecture with other styles of local architecture in Anatolia. The Ottoman Empire ushered in a centuries-long tradition of Ottoman architecture up until the early 20th century.
An earthquake occurred at 08:50:39 Pakistan Standard Time on 8 October 2005 in Azad Jammu and Kashmir, a territory under Pakistan. Its epicenter was 19 km northeast of the city of Muzaffarabad, and 90 km north north-east of Islamabad, the capital city of Pakistan, and also affected nearby Balakot in Khyber Pakhtunkhwa and some areas of Jammu and Kashmir, India. It registered a moment magnitude of 7.6 on the Richter scale and had a maximum Mercalli intensity of XI (Extreme). The earthquake was also felt in Afghanistan, Tajikistan, India and the Xinjiang region. The severity of the damage caused by the earthquake is attributed to severe upthrust. Although not the largest earthquake to hit this region in terms of magnitude it is considered the deadliest, surpassing the 1935 Quetta earthquake. Sources indicate that the official death toll in this quake in Pakistan was between 73,276 and 87,350, with some estimates being as high as over 100,000 dead. In India, 1,360 people were killed, while 6,266 people were injured. Three and a half million people were left without shelter, and approximately 138,000 people were injured in the quake.
The architecture of Istanbul describes a large mixture of structures which reflect the many influences that have made an indelible mark in all districts of the city. The ancient part of the city is still partially surrounded by the Walls of Constantinople, erected in the 5th century by Emperor Theodosius II to protect the city from invasion. The architecture inside the city proper contains buildings and structures which came from Byzantine, Genoese, Ottoman, and modern Turkish sources. The city has many architecturally significant entities. Throughout its long history, Istanbul has acquired a reputation for being a cultural and ethnic melting pot. As a result, there are many historical mosques, churches, synagogues, palaces, castles and towers to visit in the city.
An earthquake struck the Kerman province of southeastern Iran at 01:56 UTC on December 26, 2003. The shock had a moment magnitude of 6.6 and a maximum Mercalli intensity of IX (Violent). The earthquake was particularly destructive in Bam, with the death toll amounting to at least 34,000 people and injuring up to 200,000. The effects of the earthquake were exacerbated by the use of mud brick as the standard construction medium; many of the area's structures did not comply with earthquake regulations set in 1989.
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 Global Earthquake Model (GEM) is a public–private partnership initiated in 2006 by the Global Science Forum of the OECD to develop global, open-source risk assessment software and tools. With committed backing from academia, governments and industry, GEM contributes to achieving profound, lasting reductions in earthquake risk worldwide by following the priorities of the Hyogo Framework for Action. From 2009 to 2013 GEM is constructing its first working global earthquake model and will provide an authoritative standard for calculating and communicating earthquake risk worldwide.
A hazard is a potential source of harm. Substances, events, or circumstances can constitute hazards when their nature would potentially allow them to cause damage to health, life, property, or any other interest of value. The probability of that harm being realized in a specific incident, combined with the magnitude of potential harm, make up its risk. This term is often used synonymously in colloquial speech.
A hazard map is a map that highlights areas that are affected by or are vulnerable to a particular hazard. They are typically created for natural hazards, such as earthquakes, volcanoes, landslides, flooding and tsunamis. Hazard maps help prevent serious damage and deaths.
Seismic codes or earthquake codes are building codes designed to protect property and life in buildings in case of earthquakes. The need for such codes is reflected in the saying, "Earthquakes don't kill people—buildings do." Or in expanded version, "Earthquakes do not injure or kill people. Poorly built manmade structures injure and kill people".
GeoHazards International (GHI) is a 501(c)(3) non-profit organization dedicated to ending preventable death and suffering caused by natural disasters in the world's most vulnerable communities. Founded in 1991, GHI is the first non-profit, nongovernmental organization dedicated to mitigating earthquake, tsunami, and landslide risks in the world's poorest and most at-risk regions. Its solutions emphasize preparedness, mitigation, and building local capacity in order to manage risk.
Dr. Hideki "Kit" Miyamoto is a Japanese American structural engineer known for being the founder-CEO of Miyamoto International, a global structural engineering and disaster risk reduction organization. He is also the chairman of California's Alfred E. Alquist Seismic Safety Commission, which investigates earthquakes and recommends policies for risk reduction.
Omar-Darío Cardona Arboleda is a civil engineer, academic, and author. He is a Titular Professor of integrated disaster risk management and climate change adaptation in the Institute of Environment Studies at the National University of Colombia, Co-founder, and CEO of Ingeniar: Risk Intelligence.
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