1. Earthquakes I-880, Oakland, CA (October 1989)

3. Magnitude 5+ earthquakes 1980 - 1990

4. Earthquake Basics The elastic rebound theory is an explanation for how energy is spread during earthquakes.

7. Normal fault

10. Earthquake Basics  Elastic Rebound Theory: –Due to plate motion, rocks on each side of a fault are moving slowly. If the fault is “locked”, stress in the rock increases. Once they are stressed past a certain point, they fracture at their weakest point and spring back to their original shape (rebound) –Aftershocks—this release of energy often puts stress on other rocks and cause them to break and rebound too

11. Earthquake focus and epicenter

12. Types of Earthquake Waves  P (primary) waves –Compressional (push-pull) –Fastest waves (first to arrive at seismograph) –Move through all materials

13. Evidence of P-wave motion

14. Types of Earthquake Waves  S (secondary) waves –Move perpendicular to P wave –Second fastest waves (next to arrive at seismograph) –Move ONLY through solids

15. Types of Earthquake Waves  Surface waves –Rolling motion –Slowest waves (arrive last at seismograph) –Cause most damage

16. Seismometer

17. A seismogram records wave amplitude vs. time

18. Locating an Epicenter Locating an Epicenter 1.View Seismograms 2.Measure P and S wave arrivals 3.(cont’d on next slides)

19. PS

20. Locating an Epicenter 1.View Seismograms 2.Measure P and S wave arrivals 3.Measure S-wave “lag” time ( = S - P) 4.Use Travel-Time graph to correlate distance.

21. 14.7 Locating an Epicenter 1.View Seismograms 2.Measure P and S wave arrivals 3.Measure S-wave “lag” time ( = S - P) 4.Use Travel-Time graph to correlate distance. 5.Triangulate Distances

22. PRACTICE TIME!!

25. Seismogram

26. http://seismo.berkeley.edu/seismo/faq/iup/eq_local.html

32. Shadow Zone  P-waves reflect between 0-104  P-waves refract between 104-150  S-waves only reflect  Proves outer core is LIQUID!

34. Measuring Strength  Earthquake Magnitude Charles Richter designed first scaleCharles Richter designed first scale Based on height of the largest seismic waveBased on height of the largest seismic wave Every 1 increase in magnitude = 10x increase in strengthEvery 1 increase in magnitude = 10x increase in strength

35. Measuring Intensity  Earthquake Intensity A measure of earthquake shaking based on the amount of damageA measure of earthquake shaking based on the amount of damage Most often measured by the Modified Mercalli Intensity Scale (I-XII)Most often measured by the Modified Mercalli Intensity Scale (I-XII) Human basedHuman based Why needed?Why needed? Example: Central Michigan Quake 9/2/94Example: Central Michigan Quake 9/2/94

36. Earthquake Destruction  Earthquake can trigger Volcanic EruptionsVolcanic Eruptions Tsunami (seismic sea waves)Tsunami (seismic sea waves) Mass MovementsMass Movements Liquefaction of the groundLiquefaction of the ground Saturated material turns fluidSaturated material turns fluid Underground objects may float to surfaceUnderground objects may float to surface FiresFires

38. Earthquake Damage: Liquifaction

41. Tsunami Formation

42. Tsunami travel time (hours; simulation) NOAA

43. Dec. 2004 Sumatra Tsunami http://staff.aist.go.jp/kenji.satake/animation.gif

44. Current Seismic Events  Earthquakes http://earthquake.usgs.gov/recenteqs/  Tsunami http://wcatwc.arh.noaa.gov/tsunami.htm

45. References Used  http://science.howstuffworks.com/earthquake6.htm http://science.howstuffworks.com/earthquake6.htm  http://www.data.scec.org/chrono_index/bigbear.ht ml http://www.data.scec.org/chrono_index/bigbear.ht ml http://www.data.scec.org/chrono_index/bigbear.ht ml  http://pubs.usgs.gov/dds/dds- 29/web_pages/los_gatos.html http://pubs.usgs.gov/dds/dds- 29/web_pages/los_gatos.html http://pubs.usgs.gov/dds/dds- 29/web_pages/los_gatos.html  http://earthquake.usgs.gov/bytopic/photos.html http://earthquake.usgs.gov/bytopic/photos.html  http://earthquake.usgs.gov/4teachers/ http://earthquake.usgs.gov/4teachers/  http://earthquake.usgs.gov/recenteqs/ http://earthquake.usgs.gov/recenteqs/