Seismicity

What is, by definition, an earthquake?

a violent shaking of the Earth's crust

Where do 90% of earthquakes occur?

at plate boundaries

What is the main primary hazard of earthquakes?

shock waves

What are some secondary hazards of earthquakes?

• tsunamis

• liquefaction

• landslides

What are seismic waves (shock waves)?

movements of energy that travel out from the focus of an earthquake

What are the two types of seismic waves (shock waves)?

• body waves

• surface waves

What are the characteristics of body waves?

• travel through the Earth

• P (primary) waves - 3-5km/s

• S (secondary) waves - 2-3km/s

What are the characteristics of surface waves?

• travel along the Earth's surface

• Rayleigh waves - up and down

• Love waves - sideways

What is liquefaction?

The space between the grains of soil contains air and water. During an earthquake, the shaking causes particles of soil to clump together, which forces water to quickly rise upwards. As the water breaks through to the surface, it floods large areas with wet, sticky sludge.