One of the most frightening and destructive phenomena of nature is a severe earthquake and its terrible aftereffects. An earthquake is the sudden, rapid shaking of the earth, caused by the breaking and shifting of subterranean rock as it releases 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 accumulated 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.
From the lifetime of the Greek philosopher Anaxagoras in the 5th century BCE to the 14th century CE, earthquakes were usually attributed to “air (vapors) in the cavities of the Earth.Thales of Miletus, who lived from 625–547 (BCE) was the only documented person who believed that earthquakes were caused by tension between the earth and water.Other theories existed, including the Greek philosopher Anaxamines’ (585–526 BCE) beliefs that short incline episodes of dryness and wetness caused seismic activity. The Greek philosopher Democritus (460–371 BCE) blamed water in general for earthquakes. Pliny the Elder called earthquakes “underground thunderstorms.”
Did You Know?
Doorways are no stronger than any other part of a structure so don’t rely on them for protection! During an earthquake, get under a sturdy piece of furniture and hold on. It will help shelter you from falling objects that could injure you during an earthquake.
Prepare for an Earthquake
-Become aware of fire evacuation and earthquake safety plans for all of the buildings you occupy regularly.
-Pick safe places in each room of your home, workplace and/or school. A safe place could be under a piece of furniture or against an interior wall away from windows, bookcases or tall furniture that could fall on you.
-Practice “drop, cover and hold on” in each safe place. If you do not have sturdy furniture to hold on to, sit on the floor next to an interior wall and cover your head and neck with your arms.
-Keep a flashlight and sturdy shoes by each person’s bed in case the earthquake strikes in the middle of the night.
-Make sure your home is securely anchored to its foundation.
-Bolt and brace water heaters and gas appliances to wall studs.
-Bolt bookcases, china cabinets and other tall furniture to wall studs.
-Hang heavy items, such as pictures and mirrors, away from beds, couches and anywhere people sleep or sit.
-Brace overhead light fixtures.
-Install strong latches or bolts on cabinets. Large or heavy items should be closest to the floor.
-Learn how to shut off the gas valves in your home and keep a wrench handy for that purpose.
-Learn about your area’s seismic building standards and land use codes before you begin new construction.
-Keep and maintain an emergency supplies kit in an easy-to-access location.
If You Are Inside When the Shaking Starts
-Drop, cover and hold on. Move as little as possible.
-If you are in bed, stay there, curl up and hold on. Protect your head with a pillow.
-Stay away from windows to avoid being injured by shattered glass.
-Stay indoors until the shaking stops and you are sure it is safe to exit. When it is, use stairs rather than the elevator in case there are aftershocks, power outages or other damage.
-Be aware that fire alarms and sprinkler systems frequently go off in buildings during an earthquake, even if there is no fire.
If You Are Outside When the Shaking Starts
-Find a clear spot (away from buildings, power lines, trees, streetlights) and drop to the ground. Stay there until the shaking stops.
-If you are in a vehicle, pull over to a clear location and stop. Avoid bridges, overpasses and power lines if possible. Stay inside with -your seatbelt fastened until the shaking stops. Then, drive carefully, avoiding bridges and ramps that may have been damaged.
If a power line falls on your vehicle, do not get out. Wait for assistance.
If you are in a mountainous area or near unstable slopes or cliffs, be alert for falling rocks and other debris. Landslides are often triggered by earthquakes.
What to Do After an Earthquake
-After an earthquake, the disaster may continue. Expect and prepare for potential aftershocks, landslides or even a tsunami. Tsunamis are often generated by earthquakes.
-Each time you feel an aftershock, drop, cover and hold on. Aftershocks frequently occur minutes, days, weeks and even months following an earthquake.
-Check yourself for injuries and get First Aid, if necessary, before helping injured or trapped persons.
-Put on long pants, a long-sleeved shirt, sturdy shoes and work gloves to protect against injury from broken objects.
-Look quickly for damage in and around your home and get everyone out if your home is unsafe.
-Listen to a portable, battery-operated or hand-crank radio for updated emergency information and instructions.
-Check the telephones in your home or workplace to see if you can get a dial tone. Make brief calls to report life-threatening emergencies.
-Look for and extinguish small fires. Fire is the most common hazard after an earthquake.
-Clean up spilled medications, bleach, gasoline or other flammable liquids immediately.
-Open closet and cabinet doors carefully as contents may have shifted.
-Help people who require special assistance, such as infants, children and the elderly or disabled.
-Watch out for fallen power lines or broken gas lines and stay out of damaged areas.
-Keep animals under your direct control.
-Stay out of damaged buildings.
-If you were away from home, return only when authorities say it is safe to do so. Use extreme caution and examine walls, floors, doors, staircases and windows to check for damage.
-Be careful when driving after an earthquake and anticipate traffic light outages.
-Let Your Family Know You’re Safe
Know the Terms
Familiarize yourself with these terms to help identify an earthquake hazard:
Aftershock – An earthquake of similar or lesser intensity that follows the main earthquake.
Earthquake – A sudden slipping or movement of a portion of the earth’s crust, accompanied and followed by a series of vibrations.
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.
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.
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.
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.