Do Now – In Notebooks

What are some effects of earthquakes?

Why is intensity not always the same as magnitude for an earthquake?

EARTHQUAKE HAZARDSHow can earthquakes affect society?

Structural Failure

Stone and concrete Easily damaged

Wooden structures Withstand

Earthquakes Better Steel-framed

buildings High rises are

reinforced to make them earthquake resistant

Structural Failure

“Pancaking” Supporting walls of a building fail and an

intact level above falls

Aftershocks

A ground tremor caused by the repositioning of rocks after an earthquake

Land and Soil Failure

Massive landslides Earthquakes

liquefy surface materials which then behave like quicksand

Greatest damage in soft soil

Earthquake Evidence

Fault scarps Areas of great vertical offset

Tsunami

A tsunami is a series of water waves generated by a disturbance in the ocean.

How do Tsunamis form?

Tsunami sources displace water in the ocean

Gravity then acts to restore displaced water

A wave is generated that travels as an expanding ring across the ocean’s surface

Earthquake Forecasting

Calculating the probability of an earthquake

Done by following: History of Earthquakes in an area Rate at which strain builds up in the

rocks

Where do Earthquakes Occur? Earthquakes are not randomly

distributed Majority of earthquakes occur along

seismic belts (Almost 80% at Circum-Pacific Belt)

Seismic gaps Place along an active fault that has not

experienced an earthquake for a long time