EARTHQUAKE

A movement or trembling of the ground that is caused by a sudden release of energy when rocks along a fault move is an

Elastic or Plastic Deformation  –  Stretching and bending out of shape

Applied stress cause rocks to bend and stretch.  Once their elastic limit is passed the rocks snap and break, moving along the cracks faults.

Faults    Cracks in the tectonic plates where movement in different directions occurs

Force & Faults

Tension – pulls apart         Normal fault

If you were hiking, you could keep walking normally in one direction as you went up the fault and keep going.

Compression – pushes together      Reverse fault

If you were hiking you would have to stop, reverse directions to up the fault, and then reverse again

Shear – slides sideways.    Strike-slip fault

Most of the movement is sideways

Focus    The point on the fault in the interior where the energy release occurs from the earthquake.   

“F” for the point on the Fault
Epicenter   The point on the Earth’s surface, directly above an earthquake’s focus.  “E” for on the Earth surface

Locating the epicenter

     Three stations are needed to
     determine the epicenter location

Types of Earthquake/Seismic waves

P-Waves   PRIMARY Waves     Push – Pull

•      Compression Force.   
•      Waves that move through the
             Earth by causing  particles to
             move forward and back
•      Move the fastest
•      Move through liquid, solid & gas

S-Wave    SECONDARY Waves     Side to Side

• Shear Force
• “Snake” like motion
• Waves that move through the Earth by causing            particles to move at right angles
• Arrives second
• Moves only through solids 

SURFACE waves

Rayleigh waves: ground moves with  an elliptical, rolling motion

Love Waves: rock moves side-to-side and perpendicular

Surface waves cause the most destruction!

Seismograph

The instrument used to record seismic waves

Seismogram

The paper record the earthquake motion. Shows the time the P-wave arrives and then the time the S-wave arrives.    P wave at 11:01 am  and then the S-wave at 11:05 am

Richter Scale    1 to 9 scale of the energy released

Measures the ground motion (up and down or back and forth) from an earthquake to find the Earthquake’s strength

Mercalli Scale   I  to XII  scale of damage description it caused

Intensity expressed through Roman numerals and provides a description of the effects of earthquake intensity
 

San Andreas Fault

• Located in southern California
• Transform plate boundary and fault

Tsunami

• Ocean waves generated by earthquakes
• Can be as high as 100 feet
• Can travel as fast as 450 mph
• States most at risk are Hawaii, Alaska, and west coast – Washington, Oregon, and California