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
• 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!
• 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
• 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