One of the most frightening and destructive phenomena of nature is a severe earthquake and its terrible aftereffects. 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 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.
Know the Terms Familiarize yourself with these terms to help identify an earthquake hazard:
Earthquake A sudden slipping or movement of a portion of the earth's crust, accompanied and followed by a series of vibrations.
Aftershock An earthquake of similar or lesser intensity that follows the main earthquake.
Fault 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 a severe earthquake.
Epicenter 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.
Seismic Waves 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.
Magnitude 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 released than the previous whole number represents. Therefore, an earthquake measuring 6.0 is about 30 times more powerful than one measuring 5.0.
Take Protective Measures
Before an Earthquake The following are things you can do to protect yourself, your family, and your property in the event of an earthquake:
Repair defective electrical wiring, leaky gas lines, and inflexible utility connections. Get appropriate professional help. Do not work with gas or electrical lines yourself.
Bolt down and secure to the wall studs your water heater, refrigerator, furnace, and gas appliances. If recommended by your gas company, have an automatic gas shut-off valve installed that is triggered by strong vibrations.
Place large or heavy objects on lower shelves. Fasten shelves, mirrors, and large picture frames to walls. Brace high and top-heavy objects.
Store bottled foods, glass, china, and other breakables on low shelves or in cabinets that fasten shut.
Anchor overhead lighting fixtures.
Be sure the residence is firmly anchored to its foundation.
Install flexible pipe fittings to avoid gas or water leaks. Flexible fittings are more resistant to breakage.
Locate safe spots in each room under a sturdy table or against an inside wall. Reinforce this information by moving to these places during each drill.
Hold earthquake drills with your family members: Drop, cover, and hold on!
During an Earthquake Minimize your movements during an earthquake to a few steps to a nearby safe place. Stay indoors until the shaking has stopped and you are sure exiting is safe.
If you are
Take cover under a sturdy desk, table, or bench or against an inside wall, and hold on. If there isn't a table or desk near you, cover your face and head with your arms and crouch in an inside corner of the building.
Stay away from glass, windows, outside doors and walls, and anything that could fall, such as lighting fixtures or furniture.
Stay in bed - if you are there when the earthquake strikes - hold on and protect your head with a pillow, unless you are under a heavy light fixture that could fall. In that case, move to the nearest safe place.
Use a doorway for shelter only if it is in close proximity to you and if you know it is a strongly supported, loadbearing doorway.
Stay inside until shaking stops and it is safe to go outside. Most injuries during earthquakes occur when people are hit by falling objects when entering into or exiting from buildings.
Be aware that the electricity may go out or the sprinkler systems or fire alarms may turn on.
DO NOT use the elevators.
Move away from buildings, streetlights, and utility wires.
In a moving vehicle
Stop as quickly as safety permits and stay in the vehicle. Avoid stopping near or under buildings, trees, overpasses, and utility wires.
Proceed cautiously once the earthquake has stopped, watching for road and bridge damage.
Trapped under debris
Do not light a match. Do not move about or kick up dust.
Cover your mouth with a handkerchief or clothing.
Tap on a pipe or wall so rescuers can locate you. Use a whistle if one is available. Shout only as a last resort - shouting can cause you to inhale dangerous amounts of dust.
After an Earthquake
Be prepared for aftershocks. These secondary shockwaves are usually less violent than the main quake but can be strong enough to do additional damage to weakened structures.
Open cabinets cautiously. Beware of objects that can fall off shelves.
Stay away from damaged areas unless your assistance has been specifically requested by police, fire, or relief organizations.
Be aware of possible tsunamis if you live in coastal areas. These are also known as seismic sea waves (mistakenly called tidal waves). When local authorities issue a tsunami warning, assume that a series of dangerous waves is on the way. Stay away from the beach.
Knowledge Check Check your knowledge about what to do during an earthquake. For each question, choose answer A or B and circle the correct response. When you have finished, check your responses using the answer key.
What action should you take during an earthquake? The answer varies by where you are when an earthquake strikes. For each situation, pick the best course of action from the choices given.
Go out to the street
Stand by a window to see what is happening
Stay in bed and protect your head with a pillow
In any building:
Stand in a doorway
Crouch in an inside corner away from the exterior wall
On the upper floor of an apartment building:
Take the elevator to the ground floor as quickly as possible