2. III. Earthquakes and Society A. Earthquake Hazard 1. Different levels a.Measurement of how likely an area is to have damaging earthquakes in the future b. Determined by past and present seismic activity c. Variation caused by differences in seismic activity d. Greater the seismic activity, higher the hazard level e. West coast very high hazard level

3. B. Earthquake Forecasting 1. Strength and Frequency b. Scientists use statistics to forecast strength, location and frequency a. Strength related to how often they occur 2. The Gap Hypothesis a.Sections of faults with few earthquakes likely to have. strong one b. Seismic gaps – few earthquakes

4. 3. Using the Gap Hypothesis a.Not all scientists believe its accuracy in predicting b. 1988 predicted gap in Loma Prieta fault had 30% chance of 6.5 c. Earthquake in 1989 filled seismic gap; 6.9 d. Aftershocks – weaker earthquakes follow stronger eq

6. C. Earthquakes and Buildings 1. Older structures a.being made more earthquake resistant - retrofitting b. Securely fasten structure to foundation c. Steel used to strengthen structures made of brick 2. Earthquake resistant buildings a.Mass damper (1) Weight in roof of building (2) Motion sensors detect movement (3) Controls in roof shift mass damper to counteract movement

7. b. Active tendon system (1) Sensors notify computer building is moving (2) Computer activates devices to shift large weight to counteract c. Base isolators (1) Shock absorbers absorb seismic waves (2) Rubber and steel d. Cross braces (1) Placed between floors (2) Counteract side-to-side pressure

8. e. Flexible pipes (1) Help prevent water and gas lines from breaking (2) Flexible joints

10. D. Are you Prepared for an Earthquake? 1. Before the shaking starts a. Safeguard home against earthquakes b. Heavy objects near floor c. Find safe places within each room and outside of home d. make plan to meet after earthquake e. Store necessary items 2. When the Shaking starts a. Crouch or lie down under table or desk b. Outside lie face down away from building, power line, trees – cover head c. Remain in car

11. 3. After the Shaking Stops a. Try to calm down and get bearings b. Remove yourself from immediate danger d. Be aware of aftershocks c. Stay out of damaged buildings