Earthquakes:
Vibrations of the Earth’s crust.
Usually occur when rocks under stress shift suddenly along a fault.
Focus....
Focus: The area along a fault where the slippage first occurs
Epicenter: The point on the Earth’s surface directly above focus.
Earthquake waves:
When an earthquake occurs, energy is released in the form of vibrations, called seismic waves.
3 types of waves:
1) P waves
2) S waves
3) Surface waves
Foreshock: Small earthquakes that preceed a large earthquake.
Aftershocks: Small earthquakes that occur after a large earthquake.
Primary waves--P waves
Primary waves
Move fastest
Reaches seismic station first
Moves through solids, liquids & gases
The more rigid the material, the faster the
p wave travels
Secondary waves--S waves
Secondary waves
Reach the seismic stations second (after the P waves)
Can only travel through solid material
Cannot be detected on other side of Earth
because they cannot
travel through liquid
outer core
Surface waves--Rayleigh & Love
Love waves travel
perpendicular to P
waves
Rayleigh waves are
rotating waves
Surface waves are what
cause all the destruction
to buildings.
These occur when P
waves and S waves
transfer energy to
surface
Richter Scale--Measure of energy released by an earthquake
Lag Time....
The differences in arrival times of P waves and S waves to the seismic station
Richter vs. Mercalli Scale
Richter Scale--Measure of
energy released by an
earthquake
Modified Mercalli Scale: A
measure of intensity of an
earthquake or the amount of
damage it causes