8.3 Earthquakes

Earthquake Hazard Earthquake 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 Hazard

Earthquake Forecasting Seismologists 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 Frequency The strength of an earthquake is related to how often they occur.  Stronger = Less Frequent  More Frequent = Weaker

Strength and Frequency

The Gap Hypothesis Gap 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 Buildings Retrofitting – 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 Buildings

Preparing for an Earthquake Before 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 Starts Indoors ◦ 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 Stops Remove 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 8