Urban seismic risk is a subset of the general term
seismic risk
Seismic risk refers to the risk of damage from earthquake to a building, system, or other entity. Seismic risk has been defined, for most management purposes, as the potential economic, social and environmental consequences of hazardous events th ...
which describes the problems specific to centers of population when they are subjected to
earthquake
An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, fr ...
s. Many risks can be minimized with good
earthquake construction
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 ear ...
, and
seismic analysis
Seismic analysis is a subset of structural analysis and is the calculation of the response of a building (or nonbuilding) structure to earthquakes. It is part of the process of structural design, earthquake engineering or structural assessment ...
. One of the best ways to deal with the issue is through an
earthquake scenario analysis.
Toronto
Toronto
Toronto ( ; or ) is the capital city of the Canadian province of Ontario. With a recorded population of 2,794,356 in 2021, it is the most populous city in Canada and the fourth most populous city in North America. The city is the anch ...
,
Ontario
Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central C ...
, Canada is used as an example city in this article. The general issues are common to all cities subject to earthquakes.
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
The CN Tower (french: Tour CN) is a concrete communications and observation tower in downtown Toronto, Ontario, Canada. Built on the former Railway Lands, it was completed in 1976. Its name "CN" referred to Canadian National, the railway c ...
. Similar to methodologies used in
nuclear reactor
A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat fr ...
s, a seismic walk down of the city is the best way to identify vulnerabilities and possible places for improvement.
Toronto is located on the shores of
Lake Ontario
Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north, west, and southwest by the Canadian province of Ontario, and on the south and east by the U.S. state of New York. The Canada–United States border ...
, the site of much microseismicity. Historic records indicate that energetic earthquakes occur infrequently in the region, as with many other cities in the world, though Toronto was struck by a
5.0 magnitude earthquake on June 23, 2010, and a 5.1 magnitude earthquake on May 17, 2013.
Most new construction complies with strict building codes, and buildings designed for loads that go beyond seismic. For example, Toronto's highrises are, for the most part, firmly situated on bedrock (for settlement reasons), and are designed for
hurricane
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...
wind loads. They are not expected to have any problems structurally during an earthquake, although they may sway noticeably.
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. This picture shows an elevated expressway on filled land. Although there may not be total collapse, there will be sufficient damage to incapacitate the structure. Problems increase if there is the possibility for soil or
soil liquefaction.
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.
International projects
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.
Urban risk & planning
One of the disaster risk reduction themes set forth by the
projec
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.
References
External links
Realistic seismic appraisal of New York CityInfrastructure Risk Research Project at The University of British Columbia, Vancouver, CanadaPreventionWeb
{{DEFAULTSORT:Urban Seismic Risk
Earthquake and seismic risk mitigation