Causes of Earthquakes

• The crust of our earth is made up of many different “Tectonic Plates”.

• When these plates move, the ground we live on shakes.

Seismic Waves• There are three kinds of

Seismic Waves

• Primary or “P” waves.

• Secondary or “S” waves.

• Surface waves.

Primary Waves•Faster than S waves.

•Side to side motion.

Secondary Waves• Slower than P waves.

• Move at 90 degree angles to the ground.

Surface Waves• A complex combination

of P and S waves.

• Looks like waves on water

Types of Faults1. A NORMAL FAULT: • Also called a tension fault.

• Footwall up = Normal (FUN)

2. A REVERSE FAULT

• Footwall down.• Footwall down = Reverse (FDR)

3. STRIKE-SLIP FAULT.

•Two pieces slide past each other.

•San Andreas Fault in California.

Moment Magnitude Scale• The old scale was the Richter Scale.

• Moment Magnitude is more accurate because it accounts for energy released.

• MM uses:– How much the fault moved.

– How strong the rock was that broke.

– Seismic readings.

Strongest Quake Recorded

•May 22, 1960

•Chile

•Magnitude 9.5.

Triangulation•To tell where an earthquake happened and how strong it was, you need 3 seismographs.

• (S wave – P wave = Distance)

CSUFRCC

FCC

CSUFRCC

FCC