Introduction to Earthquakes and Tsunamis Eldridge Moores Distinguished

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Introduction to Earthquakes and Tsunamis Eldridge Moores Distinguished Professor Emeritus of Geology, UC Davis

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

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,

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

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

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

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

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: •

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

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

EM Page 9 “Civilization exists by geologic consent-subject to change without notice. ” -Attributed to Will Durant