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Physical attributes of an earthquake

Fractures in the earth's crust in which sections of rock have slipped past each other are called faults. The release of energy is in the form of low-frequency sound waves called seismic waves. There are thousands of earthquakes occurring annually, but most are very weak and cannot be detected by human beings. They are, however, recorded by seismographs, which are instruments designed to detect the planet's vibrations and movements. The seismic focus is the point where the earthquake originates. Directly above it, on planet's surface, is the epicenter.

Types of waves that accompany earthquakes:


• Primary (P) waves have a "push/pull" vibration.

• Secondary (S) waves have a "side-to-side" vibration.
• Surface (L) waves, named after the nineteenth-century British mathematician A.E.H. Love, travel along the surface of the planet's surface, and cause the major damage in an earthquake.

Note: P and S waves travel deep into planet, and reflect off the surfaces of its various geologic layers. S waves are unable to penetrate the liquid outer core of the planet


The sum total of the energy released by an earthquake is measured on the Richter scale. The Richter scale is as follows: Each increase by a factor of one corresponds to a 10X increase in the strength of a quake. Those above a factor of seven on the Richter scale are considered to be severe earthquakes.


Surviving an earthquake


To survive an earthquake in one of these areas, you should acquaint yourself with the causes and preparedness in the event of an earthquake. You cannot stop the earthquake from coming but you can understand and ACT!


Precautions

Duck And Cover
• Stay away from glass and hanging objects, large furniture such as china cabinets and bookcases

• Shield your face and head from falling debris
• Take cover under a heavy desk or table that can provide you with airspace
• Inner walls and door frames are the least likely to collapse
• Don’t use candles, matches or lighters if the lights go out – there may be a gas leak
• If you are in a high rise building get under a desk, stay away from windows and outside walls. Remain in the building and DO NOT use the elevators.
• If you are in a crowded public place, do not rush for the doorways.
• If you are outside, move away from utility wires and buildings
• If you are driving in your care, stop, move to the shoulder or curb away from overhead wires, under or over passes, utility poles. Stay in the vehicle, set parking brake and turn on radio to emergency broadcast information