Earthquakes

I used to sleep nude - until the earthquake. - Alyssa Milano

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. While earthquakes are sometimes believed to be a West Coast occurrence, there are actually 45 states and territories throughout the United States that are at moderate to high risk for earthquakes.


Terminology

  • 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.

Earthquake Magnitude Scale


MagnitudeEarthquake EffectsEstimated Number Each Year
2.5 or lessUsually not felt, but can be recorded by seismograph.900,000
2.5 to 5.4Often felt, but only causes minor damage.30,000
5.5 to 6.0Slight damage to buildings and other structures.500
6.1 to 6.9May cause a lot of damage in very populated areas.100
7.0 to 7.9Major earthquake. Serious damage.20
8.0 or greaterGreat earthquake. Can totally destroy communities near the epicenter.One every 5 to 10 years


Before an Earthquake

  • To begin preparing, you should build an emergency kit and make a family communications plan.
  • Fasten heavy items such as shelves, pictures and mirrors securely to walls and away from beds, couches and anywhere people sit.
  • Install flexible pipe fittings to avoid gas or water leaks. Flexible fittings are more resistant to breakage.
  • Secure your water heater, refrigerator, furnace and gas appliances by strapping them to the wall studs and bolting to the floor. If recommended by your gas company, have an automatic gas shut-off valve installed that is triggered by strong vibrations.
  • Hold earthquake drills with your family members.
  • Locate safe spots in each room under a sturdy table or against an inside wall.

During an Earthquake

  • If indoors:
    • Drop to the ground; take cover by getting under a sturdy table or other piece of furniture. 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 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.
    • Do not use a doorway except if you know it is a load-bearing doorway and it is close to you. Many inside doorways are lightly constructed and do not offer protection.
    • Do not exit a building during the shaking. Research has shown that most injuries occur when people attempt to move to a different location inside the building or try to leave.
  • If 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.
  • If outdoors:
    • Move away from buildings, streetlights, and utility wires.
    • Once in the open, stay there until the shaking stops. The greatest danger exists directly outside buildings, at exits and alongside exterior walls.
  • If trapped in 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

  • Listen to a battery-operated radio or television for the latest emergency information.
  • Expect aftershocks. These secondary shockwaves are usually less violent than the main quake but can be strong enough to do additional damage to weakened structures and can occur in the first hours, days, weeks, or even months after the quake.
  • Be aware of possible tsunamis if you live in coastal areas.
  • After it is safe to return, your safety should be your primary priority inspect utilities.
    • Check for gas leaks. If you smell gas or hear blowing or hissing noise, open a window and quickly leave the building. Turn off the gas at the outside main valve if you can and call the gas company, police and fire departments.
    • Look for electrical system damage. If you see sparks or broken or frayed wires, or if you smell hot insulation, turn off the electricity at the main fuse box or circuit breaker.
    • Check for sewage and water lines damage. If you suspect sewage lines are damaged, avoid using the toilets. If water pipes are damaged, contact the water company and avoid using water from the tap.
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