Earthquakes are a Part of Life in California
One of the most frightening and destructive phenomena of nature is a severe earthquake and its terrible aftereffects. To those of us who live and work in Orange County, earthquakes and other natural emergencies are a reality. In order to deal with this situation, emergency preparedness must become a way of life. In the event of a major earthquake or disaster, freeways and surface streets may be impassable and public services could be interrupted or taxed beyond their limits. Therefore, everyone must know how to provide for their own needs for an extended period of time, whether at work, home or on the road.
An earthquake is a sudden movement of the earth, caused by the abrupt release of strain that has accumulated over a long time. For hundreds of 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.
Sometimes, the movement is gradual. At other times, the plates are locked together, unable to release the accumulating energy. When the accumulated energy grows strong enough, the plates break free. If the earthquake occurs in a populated area, it may cause many deaths and injuries, and extensive property damage.
Familiarize yourself with these terms to help identify an earthquake hazard.
A sudden slipping or movement of a portion of the earth's crust, accompanied and followed by a series of vibrations.
An earthquake of similar or lesser intensity that follows the main earthquake.
The fracture across which displacement has occurred during an earthquake. The slippage may range from less than an inch to more than 10 yards in severe earthquakes.
The place on the earth's surface directly above the point on the fault where the earthquake rupture began. Once fault slippage begins, it expands along the fault during the earthquake and can extend hundreds of miles before stopping.
Vibrations that travel outward from the earthquake fault at speeds of several miles per second. Although fault slippage directly under a structure can cause considerable damage, the vibrations of seismic waves cause most of the destruction during earthquakes.
The amount of energy released during an earthquake, which is computed from the amplitude of the seismic waves. A magnitude of 7.0 on the Richter Scale indicates an extremely strong earthquake. Each whole number on the scale represents an increase of about 30 times more energy than the previous whole number represents. Therefore, an earthquake measuring 6.0 is about 30 times more powerful than an earthquake measuring 5.0.
How to Prepare
The following documents have been created by the California Governor's Office of Emergency Services. These documents have been designed to help you prepare your family, your work and your neighborhood for an earthquake.