8.3 Earthquakes

Earthquake HazardEarthquake HazardEarthquake hazard - is a

measurement of how likely an area is to have damaging earthquakes in the future.◦Determined by past and present

seismic activity.

Earthquake HazardEarthquake Hazard

Earthquake ForecastingEarthquake ForecastingSeismologists are not able to

predict when earthquakes are going to occur.◦seismologists have discovered

patterns in earthquakes which allow them to predict when they may occur.

Strength and FrequencyStrength and FrequencyThe strength of an earthquake is

related to how often they occur. Stronger = Less Frequent More Frequent = Weaker

Strength and FrequencyStrength and Frequency

The Gap HypothesisThe Gap HypothesisGap hypothesis – a hypothesis

that states that sections of active faults that have had relatively few earthquakes are likely to be the sites of strong earthquakes in the future.

Seismic Gap – areas along a fault where relatively few earthquakes have occurred.

Earthquakes and BuildingsEarthquakes and BuildingsRetrofitting – the

process of making older structures more earthquake resistant.

A common way to retrofit an older home:◦ Securely fasten it to

its foundation.◦ Steel can be used

to strengthen structures made of brick.

Earthquake – Resistant Earthquake – Resistant BuildingsBuildings

Preparing for an Preparing for an EarthquakeEarthquakeBefore the Shaking Starts

◦Safeguard your home against earthquakes. Put heavier objects on lower shelves. Have your home strengthened.

◦Find safe places within each room of your home and outside.

◦Plan a safe meeting space after the earthquake.

◦Store water, food, fire extinguisher, flashlight, radio, medicines, and a first aid kit in a place you can access after the quake.

When the Shaking StartsWhen the Shaking StartsIndoors

◦Crouch or lie face down under a table or desk in the center of a room.

Outdoors◦Lie face down away from buildings,

power lines, and trees and cover your head with your hands.

Car◦Stop the car and remain inside the

car.

After the Shaking StopsAfter the Shaking StopsRemove your self from

immediate danger.◦Calm down and get your bearings as

quickly as possible.Only return home when you are

told that it is safe to do so by someone in authority.◦aftershocks may cause more

damage to structures.

End of Chapter 8End of Chapter 8