What is an Earthquake?

Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip.

Caused by volcanic or magamitic activity.

Caused by other sudden stress changes in the Earth.

Strike Slip- causes worst earthquakes (transform)

Thrust- hit each other and one goes under (convergent)

Normal- pull away (divergent)

Tectonic plates move past each other causing stress. Stress causes the rock to deform.

Plastic Deformation- does not cause earthquakes.

Elastic Deformation- rock stretches then reaches a breaking point, releasing energy.

Deformed rock goes back to its original shape.

Focus and Epicenter

definitions

Focus- point inside the Earth where an earthquake begins.

Epicenter- point on Earth's surface above focus.

Primary Waves

(P waves)

A type of seismic waves that compresses and expands the ground.

The first wave to arrive from an earthquake.

(pushing slinky forward)

Secondary waves

(S waves)

A type of seismic wave that moves the ground up and down or side to side.

(shaking a jump rope)

Move along Earth's surface.

Produces motion in the upper crust.

   -Motion can be up & down

   -Motion can be around

   -Motion can be back & forth

Travel more slowly.

More destructive.

Scientists calculate the difference between arrival times of the P waves and S waves.

The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves.