• 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 displacements
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 slipping.
• 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.