Describe how earthquakes occur. Compare and contrast the different types of seismic waves. What are seismic waves? 03/02/2015

Can earthquakes occur in Chicago?

Forces within the Earth Tectonic plates are not smooth along their boundaries. They do not slide easily past one another. Rocks in the plates resist movement, resulting in stress buildup.

Earthquake Sudden slip on a fault Results in ground shaking and radiating seismic energy Causes – Volcanic activity – Tectonic plate movement

Faults A fracture in the Earth Normal, Reverse, Strike-slip – Strike-slip faults are most destructive Normal ReverseStrike-slip

Faults

Earthquake Sudden slip on a fault Results in ground shaking and radiating seismic energy Causes – Volcanic activity – Sudden stress changes in the Earth

Diagram of an Earthquake Hypocenter/Focus: point underground where the waves originate Epicenter: point on Earth’s surface directly above the focus. Seismic Waves: energy radiating around from the focus in wave form.

Seismic Energy 3 types of waves – Primary, Secondary, Surface

1. Primary wave (P-wave)

Causes rocks to be squeezed and pushed parallel to the direction of the wave. Fastest wave.

2. Secondary waves (S-waves)

2. Secondary Wave (S-wave) Causes rocks to move perpendicular to the wave direction Slower than P-waves

P-waves and S-waves are both BODY waves because they pass through Earth’s interior.

3. Surface Wave Travel only along Earth’s surface Cause the ground to move sideways and up and down Most destructive

3. Surface Wave

Seismic Energy