Earthquake Destruction & Dangers

The major causes of earthquake damage

• Soil conditions

• Aftershocks

• Tsunamis

Soil Conditions

• Layers of loosely packed soil, high in moisture can lead to–Liquefaction

–Landslides

Liquefaction• Loosely

packed soil turns into mud.

• Most likely to occur in soil saturated with water.

Can occur…

• when filled land is shaken violently.

• where steep slopes are found.

Landslides

Aftershocks

• An earthquake that occurs after a larger earthquake in the same area.

• They can occur hours, days, or even months later.

• Buildings already weak from the original earthquake can topple due to aftershocks.

Tsunamis • Earthquake jolts the ocean floor, it

pushes water out of the way.• This displaced water forms large

waves called tsunamis.– In the open ocean, the height of the

tsunami wave is not high at all.

– As the wave gets closer to land and the water gets shallower, it pushes up into a tall wall of about 30 meters (100 ft).

YouTube:CBS News

Asian Tsunami

YouTube:Tsunami Animation

TsunamisHawaii Tsunami

How do we prepare for earthquake damage?

• Base-isolated buildings

–Buildings designed to absorb energy from earthquakes.

–Rest on shock absorbing springs which cause the building to move back and forth without violently shaking.

Protecting Structures

Monitoring Faults

Instruments for short-range predictions

• creep meter

• laser-ranging

• tiltmeter

• satellites

Creep meter• measures HORIZONTAL movement

along a fault line. (Transform boundary – strike-slip fault)

• a wire is placed across the fault – it is attached to a weight that can slide if

the fault moves.– Geologists measure how much the weight

has moved.

Faults & Earthquakes

Laser-ranging device• measures HORIZONTAL movement.• The laser is on one side of the fault and a reflector is

on the other side of the fault.• Any change in the time needed for the laser beam to

travel across to the reflector and back indicates fault movement.

• The more time it takes, the farther the reflector is getting as the fault moves.

Tiltmeter• measures VERTICAL

movement • It consists of two bulbs that

are filled with a fluid and connected by a hollow tube.

• If the land rises or falls, fluid will flow from one bulb to the other.

• Each bulb contains a scale to measure the depth of the fluid.

Satellite monitoring• A satellite measures VERTICAL

movement.• It bounces waves off the ground and back

into space measuring the distance between the satellite and the ground.

• If the distance from the satellite to the ground changes, then geologists can detect changes in elevation.

YouTube:Monitoring Himalayas

Why can’t scientists predict the exact time and place an

earthquake is going to occur?

Even though a fault can be monitored, it is still impossible for geologists to know exactly WHERE on the fault the stress

will be released.