Earthquake Preparedness

What is an earthquake?

An earthquake is a sudden shaking of the earth caused by the breaking and shifting of rock beneath the earth's surface. 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 move slowly 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 causing the ground to shake. Most earthquakes occur at the boundaries where the plates meet; however, some earthquakes occur in the middle of the plates. Earthquakes strike suddenly, without warning; they can occur at any time of the year and at any time of the day or night.

To learn more about earthquakes, aftershocks, foreshocks, and faults, read the "Earthquake Basics" at

More information about earthquakes in Southern California may be found at

What are some of the effects of an earthquake?

Ground shaking from earthquakes can collapse buildings and bridges; disrupt gas, electric, water, and phone services; and sometimes trigger landslides, avalanches, flash floods, fires, and huge destructive ocean waves called tsunamis. When an earthquake occurs in a populated area, it may cause deaths, injuries, and extensive property damage. Most earthquake-related injuries result from collapsing walls, flying glass, and falling objects as the result of ground shaking, or people trying to move more than a few feet during the shaking. Buildings with foundations resting on unconsolidated landfill and other unstable soil, and trailers or homes not tied to their foundations, are at risk because they can be shaken off their mountings during an earthquake.

What to do before an earthquake happens:

Get prepared before an earthquake strikes! Listed below are some steps that you can take to prepare now:

1. Create an emergency plan for your family or business.

Click on these links for additional information on creating an emergency plan: Family Emergency Plan or Business Preparedness.

2. Prepare emergency supply kits.

Click here for more information on how to build an emergency supply kit.

3. Secure household items and strengthen your home.

To increase your earthquake safety, begin identifying hazards in your home and begin fixing them. By securing household items and strengthening your home, you can prevent damage and reduce injury. Below are a few on-line resources that will provide you with some recommended actions for making your home a safer place:

Secure Your Building

Step No. 1: Identifying Hazards in your Home

Step No. 4: Identifying and Fixing your Home’s Weaknesses

4. Conduct a "Drop, Cover, and Hold On" drill with your family or coworkers.

Visit for resources to assist you in planning your drill.

What to do during an earthquake:

The most important thing you can do when an earthquake occurs is protect yourself!

If you are indoors when an earthquake occurs, "Drop, Cover, and Hold On." Drop to the floor, take cover under a sturdy desk or table, and hold on to it firmly. Be prepared to move with the desk or table until the shaking stops. If you are not near a desk or table, drop to the floor against an interior wall and protect your head and neck with your arms. Avoid exterior walls, windows, hanging objects, mirrors, tall furniture, large appliances, and kitchen cabinets with heavy objects or glass. Do not go outside!

Click on the link below for more information on how to protect yourself during an earthquake. This website will provide you with information on what to do if you are outdoors, in bed, driving, in a high-rise, in a stadium, or below a dam when an earthquake occurs:

What to do after an earthquake:

1. Check for injuries and damage.

When the shaking stops, assess your situation. If you are safe, help others and check for damage. If people are injured, you may need to perform first-aid measures or administer rescue breathing. When checking for damage, you may need to extinguish small fires, shut off a gas valve if you suspect a gas leak, shut off the power to your house if there is damage to electrical wiring, and so on. For more detailed information about checking for injuries and damage, please visit the following website:

2. Follow your emergency plan.

Once your situation has stabilized continue to follow the emergency plan you prepared before the earthquake occurred. Aftershocks may continue to occur, so always be ready to drop, cover, and hold on. Click on the following link for more information about what to expect in the first days and weeks after an earthquake:

Did you know?

Personal experiences of the effects of an earthquake are very valuable to scientists. When you feel a quake (and it is safe to do so), report your observations by using the quick survey found on the U.S. Geological Survey, "Did you feel it?" website at

The Richter scale was developed by Charles F. Richter in 1935. It is a logarithmic measurement of the amount of energy released by an earthquake. Earthquakes with a magnitude of at least 4.5 are strong enough to be recorded by sensitive seismographs all over the world. For more information about how earthquakes are measured, visit here for earthquake measuring site.

The effects of earthquakes are also measured by the Modified Mercalli Intensity scale. The intensity of a quake is evaluated according to the observed severity of the quake at specific locations. The Mercalli scale rates the intensity on a Roman numeral scale that ranges from I to XII.

Additional sources of information on earthquakes and ways you can prepare:

California Earthquake Authority

California Integrated Seismic Network

Dare to Prepare

Drop, Cover, and Hold On

Earthquake Country Alliance - English – Spanish

Southern California Earthquake Center

The Great California Shake Out

U.S. Geological Survey

California Geological Survey (State of California, Department of Conservation)

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