An earthquake is ground shaking caused by a sudden movement of rock in the earth's crust. Such movements usually occur along faults, which are thin zones of crushed rock separating blocks of crust. When one block suddenly slips and moves relative to the other along a fault, the energy released creates vibrations called seismic waves that radiate up through the crust to the Earth's surface, causing the ground to shake.
Earthquakes may last only a few seconds or may continue for up to several minutes. They can occur at any time of the day or night and at any time of the year. They are caused by stress that builds up over time as blocks of crust attempt to move but are held in place by friction along a fault. (The earth's crust is divided into large plates that continually move over, under, alongside or apart from one another atop the partly molten outer layer of the earth's core.) When the pressure to move becomes stronger than the friction holding them together, adjoining blocks of crust can suddenly slip, rupturing the fault and creating an earthquake.
In addition to ground shaking, earthquakes can also generate secondary hazards such as landslides, avalanches, surface faulting, tsunamis, liquefaction and flash floods. For more information on secondary hazards, visit How Do Earthquakes Affect People? on the FEMA website.
To learn more about the science of earthquakes, visit the U.S. Geological Survey (USGS) Earthquake Hazards Program.
Vertical Slice Through a Subduction Zone
One of the many tectonic plates that make up earth's outer shell descends or "subducts," under an adjacent plate. This kind of boundary between plates is called a "subduction zone." When the plates move suddenly in an area where they are usually stuck, an earthquake happens (Source: www.usgs.gov).
Thousands of earthquakes occur in the United States each year; most are too small to significantly affect businesses and communities. However, large and very damaging earthquakes have occurred in the past and could happen again at anytime. Unlike other natural hazards such as hurricanes, floods and others, an earthquake is a no-notice event that cannot be predicted. Therefore, it is more important for the private sector and the communities to understand their risks, make a mitigation project plan and take earthquake mitigation actions to ensure safety and stay in business.
|Did You Know?|
|Small businesses alone account for more than 99 percent of all companies with employees, employ 50 percent of all private sector workers, and provide nearly 45 percent of the Nation's payroll.|
Today, businesses of all types and sizes serve as the backbone of every community and the nation's economic strength. Small businesses alone account for more than 99 percent of all companies with employees, employ 50 percent of all private sector workers and provide nearly 45 percent of the nation's payroll. If businesses are unable to continue operations after an earthquake event, this could impact effective flow of critical products and services (i.e. food, medicine, utilities, financial, etc.), limit individual and community livelihood and significantly delay disaster recovery.
In general, many businesses have invested in emergency management and continuity of operations planning. However, most businesses have not conducted earthquake mitigation measures to protect their assets, staff and business operations. During an earthquake, buildings—or their components or contents— can be collapsed, toppled, broken apart, tossed around or rendered inoperable or unusable. The same can happen to lifeline infrastructure systems and their components, including those related to transportation, such as roads, bridges, railways, ports and airports, and those related to utilities, such as distribution lines for water, wastewater, electric power, telecommunications, natural gas and liquid fuels. Damage incurred from these hazards, such as broken gas or water pipes, can itself be hazardous, generating further damage by igniting fires or flooding buildings.
|Did You Know?|
|Most businesses have not conducted earthquake mitigation measures to protect their assets, staff and business operations.|
Hazards such as structure failure, falling, collapsing or airborne objects, earthquake- induced fires or flooding and others can also cause serious casualties. In addition to casualties, individuals can incur direct economic losses, either personal or business- related, resulting from damage to existing property. Businesses can temporarily lose the ability to generate income, due to other business and employment interruptions or terminations brought about by damage to private property or public infrastructure.
Many businesses understand the concept of emergency management and continuity planning. But these could be complex issues depending on their particular industry, size and scope as well as their level of risks from natural and man-made hazards. All businesses must account for all of their exposed, relevant hazards in order to reasonably stay in business. Guidance to all-hazards, business preparedness and continuity exist via Ready.gov, Open for Business®, and Disaster Resistant Business Toolkit.
As part of addressing all-hazards, it is critical for businesses to also incorporate actionable earthquake mitigation solutions into their planning and business decisions. By doing so, businesses protect the organization's assets (people, property, operations); sustain the capability to provide goods and/or services to customers and/or its supply chain; maintain cash flow; preserve competitive advantage and reputation and provide the ability to meet legal, regulatory, financial and contractual obligations.
Businesses in and around Seattle, WA were damaged by the February 2001 earthquake (FEMA NEWS Photo).