An earthquake is a sudden, rapid shaking of the ground caused by the breaking and shifting of rock beneath the Earth's surface. This shaking can cause damage to buildings and bridges; disrupt gas, electric, and phone service; and sometimes trigger landslides, avalanches, flash floods, fires, and huge, destructive ocean waves (tsunamis). Buildings with foundations resting on unconsolidated landfill, old waterways, or other unstable soil are most at risk. Buildings or trailers and manufactured homes not tied to a reinforced foundation anchored to the ground are also at risk since they can be shaken off their mountings during an earthquake. All 50 states, five U.S. territories and the District of Columbia are at some risk for earthquakes. Earthquakes can occur at any time of the year.
For millions of years, the forces of plate tectonics have shaped the earth, as the huge plates that form the earth’s surface slowly move over, under and past each other. At times, the movement is gradual. At other times, the plates are fused together, unable to release accumulated energy. When the accumulated energy grows great enough, the plates break free.
When an earthquake occurs in a populated area, it may cause deaths and injuries as well as extensive property damage. Ground movement during an earthquake is seldom the direct cause of death or injury. Most earthquake-related injuries result from collapsing walls or floors, flying glass, and falling objects as a result of the ground shaking or people trying to move more than a few feet during the shaking. Much of the damage in earthquakes is predictable and preventable.
The video of the Great Alaska Earthquake of 1964 shows the destruction that can occur. During earthquakes liquefaction can occur. During the Alaska Earthquake of 1964, a landslide also occurred in the Turnagain Heights area. The landslide is believed to have been caused by liquefaction. Liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is entirely filled with water. This water exerts a pressure on the soil particles that affects how tightly the particles themselves are pressed together. Prior to the earthquake, the water pressure is relatively low. Earthquake shaking can cause the water pressure to increase to the point where the soil particles can readily move with respect to each other.The highest hazard areas are concentrated in regions of man-made landfill, especially fill that was put in place many decades ago in areas that were once submerged. These types of areas are found in San Francisco, Oakland and Alameda Island, as well as other places around San Francisco Bay. Other potentially hazardous areas include larger stream channels, which produce the loose young soils that are particularly susceptible to liquefaction.
These webpages provide information on hazards that earthquakes cause, earthquake preparedness, and precautions that workers and employers should take after an earthquake has occurred.
The Preparedness page discusses ways for employers and workers to prepare for an earthquake by developing an emergency response plan and conducting workplace training. Preparedness includes planning for an earthquake before it occurs, equipping workers with information and emergency supply kits, training, and implementing preparedness plans.
The Response/Recovery page provides useful details on the hazards to avoid after an earthquake. This includes areas to avoid when using a vehicle, and safety and health hazards arising from collapsing walls, falling objects and debris, for example.
Each employer is responsible for providing a safe and healthful workplace for its workers. Employers are required to protect workers from the anticipated hazards associated with the response and recovery operations that workers are likely to conduct. For additional information on Workers' Rights, Employer Responsibilities, and other services OSHA offers, visit OSHA's Employers Page, Workers Page and Publications.
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