GEOL 100: Earthquakes

Earthquakes are the result from what? Which theory explains this?

1. rapid release of energy (stored in rocks)

2. Elastic rebound theory

Where is energy released at? Where does most of the damage occur?

1. Focus (hypocenter)

2. Epicenter or along the Fault Plane

What are faults?

They are large fractures in the Earth’s crust that may form during an earthquake

What kind of faults are defined by the vertical movement of the hanging wall and the footwall?

Dip slip

• If hw goes DOWN and fw goes UP = Normal Fault

• If hw goes UP and fw goes DOWN = Reverse fault 

Strike slips are defined by what?

By left or right horizontal movement

What kind of fault is the San Andreas Fault?

Right lateral strike-slip fault

What kind of form does earthquake energy travel in?

Seismic waves

P-waves are…

compressional body wave that cause forward and backward ground movement (like a slinky)

S waves are…

a shear body wave that cause up and down ground movement (like a rope)

L- waves (love waves) are…

a slow tranverse surface wave that cause side-to-side ground movement (like a snake)

R-waves are…

a slow rolling surface wave that causes horizontal and vertical ground movement

What records seismic waves on a seismogram?

a Seismic

What scale is used to describe the severity of ground shaking based on observed damage?

The Modified Mercalli Intensity Scale 

The Richter Scale measures what? What is it based on?

The Local Magnitude (ML) and is based on the amplitude and travel times of seismic waves

What does the Moment Magnitude determine?

The size of an earthquake based on the area of fault rupture, the average amount of fault rupture, and the force required to cause the rupture

Earth’s largest earthquakes occur where?

at Subduction Zones and may result in Tsunami