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Magnitude 8.9 (9.0) earthquake near Sendai,

Magnitude 8.9 (9.0) earthquake near Sendai, east coast of Honshu, Japan Friday, March 11, 2011 at 05:46:23 UTC .

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Magnitude 8.9 (9.0) earthquake near Sendai,

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  1. Magnitude 8.9 (9.0) earthquake near Sendai, east coast of Honshu, JapanFriday, March 11, 2011 at 05:46:23 UTC Japan was struck by a magnitude 8.9 (9.0) earthquake off its northeastern coast last Friday. This the largest earthquake that Japan has experienced since measurements began. Part of houses swallowed by tsunami burn in Sendai, Miyagi Prefecture (state) after Japan was struck by a strong earthquake off its northeastern coast Friday, March 11, 2011. New York Times

  2. This is about the 5th largest earthquake since 1900 9.6 9.4 9.2 9.0 8.8 8.6 8.4 8.2 8.0 Chile 1960 Sumatra 2004 Alaska 1964 Russia 1952 Ecuador 1906 Japan 2011 Chile 2010 magnitude Alaska 1965 1900 1920 1940 1960 1980 2000 2020 year

  3. Japan is one of the most seismically active areas in the world

  4. The event occurred where the Pacific and North American plates converge at a rate of 8.3 cm/year Japan Trench USGS

  5. The seismicity of the plate boundary outlines a subduction zone Seismicity Cross Section across the subduction zone showing the relationship between color and earthquake depth. Images courtesy of the US Geological Survey

  6. 371 aftershocks, M > 5, in the first two days after the event outline the fault area ERI, Univ. Tokyo

  7. The focal mechanism was a thrust fault Looking from the side 10 - 15 Looking from below ERI first motion sense of motion USGS centroid (average) sense of motion

  8. A slip model The maximum slip was about18 m The vertical movement of the ocean bottom was up to 2 m and distributed over a 450 km x 150 km fault ERI, Univ. Tokyo

  9. The event was complete in 2.5 minutes The rupture took about 30 seconds in each point but took 150 seconds to propagate from the focus to other parts of the fault. USGS centroid solution Moment release rate (dyne cm/s) time (seconds)

  10. Initiation of tsunami We model the vertical movement of the ocean bottom due to the event (2 m). The water mass is lifted up by 2 m in 2-3 minutes over an area of 500x150 km and does not have time to flow down the slopes on the sides

  11. Initial propagation of tsunami Pacific Japan The initial water bulge expands. The sea level depression on the landward side draws water from the coast. The surface deflection propagates as a gravity surface wave . The wave speed is: H = water depth, g = gravity The shallower the water, the lower the speed. Therefore, as the tsunami enters shallow waters the wave “piles up”. The non-linear effects of shallow water magnification are difficult to model. Also, complex focussing effects occur in sounds and bays.

  12. Calculated tsunami timing and maximum amplitude In the deep ocean we can model the timing and amplitude distribution of the tsunami with precision. NOAA

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