What is an Earthquake?

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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.

What are the 3 types of faults and definitions?

Strike Slip- causes worst earthquakes (transform)

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

Normal- pull away (divergent)

What causes earthquakes?

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

What are the Plastic and Elastic Deformation definitions?

Plastic Deformation- does not cause earthquakes.

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

Elastic Rebound

Deformed rock goes back to its original shape.

Focus and Epicenter


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)

Comparing P waves and S waves
Surface Waves

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.

How do Scientists calculate how far a location is from the epicenter of an earthquake?

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.