1. Earthquakes

2. Quake Damage

4. Car sunk into liquefied ground, New Zealand

5. Quake Damage Videos Japan liquefaction March 2011 Japan swimming pool Japanese Tsunami, March 2011

6. Earthquakes What is an Earthquake? Seismology Locating Earthquake Epicenters Measuring Earthquake Intensity

7. Terms Fault –Break in rock along which there has been significant movement Failure –Sudden movement on a fault that releases seismic energy Magnitude –Energy released by an earthquake

8. Terms Propagation –Movement of a wave through a medium Medium –Material through which a wave passes

9. What is an Earthquake?

10. Earth vibration –Usually caused by movement on a fault Seismic energy propagates through planet’s interior in all directions GEOL131: Earthquakes

11. What is an Earthquake? Strain energy is stored up along a fault over time Fault failure –sudden movement releases accumulated strain as seismic waves GEOL131: Earthquakes

12. Strain and Failure GEOL131: Earthquakes: What is an Earthquake?

13. What is an Earthquake? Foreshocks and aftershocks –Smaller movements before and after a large earthquake –Aftershocks can cause as much or more damage as main quake Structures already weakened People not prepared GEOL131: Earthquakes

14. Seismology

15. Study of earthquake waves Main tool: seismograph –Measures seismic wave magnitudes GEOL131: Earthquakes

16. Seismology GEOL131: Earthquakes -Platform with rolling drum moves with ground -Height of trace indicates wave strength -Weight with stylus stays in place due to inertia

17. Types of Seismic Waves GEOL131: Earthquakes: Seismology P-waves: compressional motion; fastest S-waves: transverse motion; don’t move through fluids Surface waves: orbital motion, slowest, most damaging P-waves S-waves Surface waves

18. Seismograph Traces GEOL131: Earthquakes: Seismology P-waves arrive first Delay between P- and S-wave arrivals is a function of distance from epicenter Longer delay = further from epicenter

19. Locating Earthquake Epicenters

20. Epicenter Triangulation GEOL131: Earthquakes: Locating Epicenters S-P interval: delay between P- and S- wave arrivals S-P = 5 min. S-P = 7 min. S-P = 11 min.

21. Epicenter Triangulation GEOL131: Earthquakes: Locating Epicenters If S-P = 5 mins, distance to epicenter is 3500 km Repeat for other two stations Travel-time curve

22. Epicenter Triangulation GEOL131: Earthquakes: Locating Epicenters Plot distances on globe as circles Point where circles intersect is epicenter Epicenter Travel-time curve

23. Measuring Earthquake Intensity

24. Mercalli Intensity Scale GEOL131: Earthquakes

25. Richter Magnitude Scale GEOL131: Earthquakes

26. Richter Magnitude Scale GEOL131: Earthquakes For every increase of 1, ten-fold increase in energy released Richter magnitude 4 releases 1,000 times as much energy as magnitude 1 –10x10x10

27. Moment Magnitude Scale GEOL131: Earthquakes Preferred by seismologists –Most accurate for large earthquakes Uses the following factors: –Total movement on fault –Depth of movement on fault –Rock strength

28. Hawaiian lava threatens homes

29. End of Chapter