1. Earthquakes and Related Phenomena

2. Earthquake Web Resources http://earthquake.usgs.gov/

3. Deadliest Earthquakes on Record

4. Introduction to Earthquakes ~ 1 million earthquakes a year Change of 1 M w = ~30 X energy Great earthquakes; M s >8 Major earthquakes; M s =7-7.9 (widespread damage) Moderate earthquakes: M s =6 (considerable damage) Population factors: density, land use, and building construction M s Earthquakes/year 8.5 - 8.9 0.3 8.0 - 8.4 1.1 7.5 - 7.9 3.1 7.0 - 7.4 15 6.5 - 6.9 56 6.0 - 6.4 210

5. Where do earthquakes occur? Plate boundaries, but not only – intraplate earthquakes are also common

6. Earthquake Occurrence Most occur along plate boundaries. –Loma Prieta (1989) –North Ridge (1994) Intraplate earthquakes –Can be large and quite damaging. New Madrid zone is a foundered rift zone Salt Lake City and south into New Mexico Charleston, S.C.

7. Largest US Earthquakes

8. Relationship of Earthquakes to Faults

9. Earthquake Processes Faults, Folds & Concealed Faults, and Movement –Fractures Faults are fractures or systems along which rocks have been displaced –Model: brick -bungee cord on a winch; sand paper Joints are fractures and fractures systems along with rocks have NOT been displaced Slip rate aver. long-term rate of movement ( mm/yr or m/1000 yrs); risky measurement Seismic waves produced by rupture Faults-seismic sources; used to evaluate the earthquake risk in a given area

10. Earthquake Processes Fault types Strike-slip faults only have horizontal displacement (right- or left-lateral)Strike-slip faults Normal faults occur where the hanging wall moves down with respect to the foot wall; results in crustal extension Reverse faults occur when the hanging wall moves up with respect to the foot wall; results in crustal shortening; low fault plane angle ( less than 45°)= thrust fault Oblique faults have both horizontal and vertical components Buried faults may cause earthquakes and have to surface expression

11. Faults – Understanding Strike and Dip