6.4 Earthquake safety Key concepts: How do geologists determine earthquake risk? What kinds of damage does an earthquake cause? What can be done to increase earthquake safety and reduce earthquake damage? Key terms: Liquefaction Aftershock Tsunami Base-isolated building

Earthquake risk Geologists can determine earthquake risk by locating where faults are active and where past earthquakes have occurred. Look at figure 18 (page 187) In the US, the risk is highest along the pacific coast. Plates meet along there, causing many active faults. Eastern US has fewer earthquakes because it lies farther away from plate boundaries.

Earthquake damage Causes of earthquake damage include shaking, liquefaction, aftershocks, and tsunamis.

Shaking Shaking produced by seismic waves can trigger landslides or avalanches. Shaking an also damage or destroy buildings and bridges, topple utility poles, and fracture gas and water mains. The types of rock and soil determine where and how much the ground shakes. Loose soil shakes more violently than solid rock, so the most damage may occur far away from the epicenter.

Liquefaction Occurs when an earthquake’s violent shaking suddenly turns loose, soft soil into liquid mud. It is likely where the soil is full of moisture.

Aftershocks Aftershocks are earthquakes that occur after a larger earthquake in the same area

Tsunamis A large wave from the displacement of water Sometimes occur after earthquakes because the earthquake jolts the ocean floor and water gets pushed out of the way

Earthquake safety The best way to protect yourself (your book says) is to drop, cover, and hold. Really the best way is to hover way up in the air like superman and just not deal with any of the bidness below. But, short of that, I guess drop cover and hold. Or whatever.

Designing safer buildings To reduce earthquake damage, new buildings must be made stronger and more flexible. Older buildings may be modified to withstand stronger quakes. New homes are anchored below the soil. Bridges are built on supports that go through soft soil to firmer ground.

Base isolated buildings Designed to reduce the amount of energy that reaches the building during an earthquake. A base isolated building rests on shock absorbing rubber pads. The pads smooth out the bumpy ride.

Making utilities safer Flexible joints can be installed so gas and power lines don’t break Automatic shut off valves keep da peeps safe