Introduction to Earthquakes and Tsunamis Eldridge Moores Distinguished
- Slides: 10
Introduction to Earthquakes and Tsunamis Eldridge Moores Distinguished Professor Emeritus of Geology, UC Davis California Senate Energy Committee Senator Alex Padilla, Chair, April 14, 2011
Fig. 1 -2 Fig. 1 -1 Folds EM Page 1 Coast Ranges LA region San Andreas Divergent margin Transform margin Plate tectonics of the Earth Moores & Twiss, 1995 Tahoe V. , Death Valley. San Andreas F. Faults and plate margins California examples LA basin, Cascade “megathrust”, C. Ranges Convergent/subduction margins (After Google Images)
EM Page 2 Faults: • Shaking depends on size of e. q. , distance, and nature of ground--greatest in loose sediments, less on bedrock Tsunamis: • Result from change in ocean bottom shape and depth. • Involve entire water column, not just near-surface. • Velocities about 500 mph in deep ocean, 30 -60 mph near shore, where water bunches up. • Near shore: may be focused or dispersed depending on the shape of the sea floor. • Principal Causes: • Earthquakes • Landslides • Explosive volcanic eruptions in shallow ocean
EM Page 3 Fig. 3 -1 Fig. 3 -2 Fig. 3 -3 After Atwater et al. (2005) USGS Prof. Pap. 1707
Fig. 4 -1 Fig. 4 -2 “Megathrust” EM Page 4 M 9, 1700 Ca sc ad e M 9 2011 Vancouver I. HB M 7. 9 1906 M 71989 DC M 7. 9 1857 SO (After Moores & Twiss, 1995)
Fig. 5 -1 1700 EM Page 5 HB 1906 -Hosg regorio San G 1857 DC ri SO (Moores & Twiss, ibid)
EM Page 6 Fig. 7 -1 HB Atwater et al, 2005 Cascade tsunami model Fig. 7 -2 (Atwater et al, 2005) After NRC Can.
EM Page 7 World’s largest Landslide Possible landslide locations that may cause tsunamis: • Hawaii • Basins off southern CA Hawaiian Islands Tsunami in Australia? Santa Barbara 1812 eq & “waves” Fig. 8 -2 ACTIVE: 10 cm/yr Fig. 8 -1 After Moore et al. , (1989) LA SO faults Cliffs on ridges=landslides?
EM Page 8 CONCLUSIONS: • California is on an tectonic plate margin that has been active for millions of years, and will likely continue for millions of years. • Active plate margins involve infrequent unpredictable events with large consequences. • As Californians, we can expect a future earthquake/tsunami event as large as the recent Japan, event, possibly in our lifetime. • We need to prepare present and future structures and emergency procedures accordingly. • We still have much to learn about Earth processes, and there may well be geologic surprises in our future.
EM Page 9 “Civilization exists by geologic consent-subject to change without notice. ” -Attributed to Will Durant