Body Waves: S wave

1. Body Waves: S wave

2. Surface Waves Rayleigh waves Love waves Free body oscillations >

3. From IRIS Free Body Oscillations Torroidal Modes Spherical Modes

10. h USGS Foreshocks, Aftershocks

11. USGS

13. Bolivar Peninsula, Texas

14. Bolivar Peninsula, Texas

17. Earthquake Magnitude

18. Richter Scale, ML

19. Each increment in log scale implies 10-fold change in linear scale

20. ML is logarithmic inamplitude of shaking • i.e., if A = 2 cm for ML = 5, what is A for ML = 6?

21. ML is logarithmic inamplitude of shaking • i.e., if A = 2 cm for ML = 5, what is A for ML = 6?A = 20 cm

22. ML is logarithmic inamplitude of shaking • i.e., if A = 2 cm for ML = 5, what is A for ML = 6?A = 20 cm • i.e., ifA = 10 μm for ML = 3.7,what is A for ML = 1.7?

23. ML is logarithmic inamplitude of shaking • i.e., if A = 2 cm for ML = 5, what is A for ML = 6?A = 20 cm • i.e., ifA = 10 μm for ML = 3.7,what is A for ML = 1.7?A = 0.1 μm

24. ML is logarithmic to base 32 for energy of earthquake • i.e., how much more energy does ML = 5 earthquake have than ML = 4? M=5 E M=4

25. ML is logarithmic to base 32 for energy of earthquake • i.e., how much more energy does ML = 5 earthquake have than ML = 4?32 × more energy! M=5 E M=4

26. ML is logarithmic to base 32 for energy of earthquake • i.e., how much more energy does ML = 5 earthquake have than ML = 4?32 × more energy! • i.e., how much more energy does ML = 6.5 earthquake have than ML = 4.5?

27. ML is logarithmic to base 32 for energy of earthquake • i.e., how much more energy does ML = 5 earthquake have than ML = 4?32 × more energy! • i.e., how much more energy does ML = 6.5 earthquake have than ML = 4.5?32 × 32 ~ 1,000 × more energy! • Rule: energy increases by order of 1,000 for every increment of 2 in Magnitude

28. Frequency Spectrum of Waves

29. Analogy: Music

31. Analogy: Music • Earthquake waves = mixture of S, P, surface waves of various frequencies • Music = mixture of P waves of various frequencies • Bass = low frequency • Midrange = medium frequency • Treble = high frequency • Most important point: big earthquakes make different music than small earthquakes

32. Bass Midrange Treble

33. Problem with measuring large earthquakes

34. Richter scale tuned to these earthquakes Small earthquake Big earthquake Louder Longer Lower frequency

35. Saturation

36. Moment Magnitude Scale, MW Energy ~ Rupture Area × Slip Distance × Rock Strength

37. Gutenberg-Richter • Plots LOG(frequency) or LOG(RI) vs. magnitude RI (years) Magnitude M

38. Gutenberg-Richter RI (years) Magnitude M

39. Magnitude vs. Intensity

40. Earthquake Intensity

42. 1811 New Madrid (M=7.5) 1906 San Francisco(M = 8.3)

43. Epicenter

44. S waves Close L waves R waves Far Auroville Earth Institute

45. Amplification Sedimentary basin forming

46. Amplification from wave slowing Energy depends on: Speed Amplitude

47. Amplification from focusing

48. Amplification from reflection

49. Example: 1989 Loma Prieta earthquake, California Fort Mason built on solid bedrock Marina district built on fill

50. Amplification damage, Marina District, San Francisco