Tsunami generation by horizontal displacement of ocean bottom

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95068/1/grl9126.pd

Fault parameters of the 1896 Sanriku Tsunami Earthquake estimated from Tsunami Numerical Modeling

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95213/1/grl9350.pd

The Sanriku‐Oki, Japan, Earthquake of December 28, 1994 (M w 7.7): Rupture of a different asperity from a previous earthquake

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95083/1/grl9251.pd

Unusual rupture process of the Japan Sea earthquake

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94722/1/eost9791.pd

The great Kurile Earthquake of October 4, 1994 tore the slab

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94905/1/grl8448.pd

What controls the lateral variation of large earthquake occurrence along the Japan Trench?

The lateral (along trench axis) variation in the mode of large earthquake occurrence near the northern Japan Trench is explained by the variation in surface roughness of the subducting plate. The surface roughness of the ocean bottom near the trench is well correlated with the large-earthquake occurrence. The region where the ocean bottom is smooth is correlated with‘typical’large underthrust earthquakes (e.g. the 1968 Tokachioki event) in the deeper part of the seismogenic plate interface, and there are no earthquakes in the shallow part (aseismic zone). The region where the ocean bottom is rough (well-developed horst and graben structure) is correlated with large normal faulting earthquakes (e.g. the 1933 Sanriku event) in the outer-rise region, and large tsunami earthquakes (e.g. the 1896 Sanriku event) in the shallow region of the plate interface zone. In the smooth surface region, the coherent metamorphosed sediments form a homogeneous, large and strong contact zone between the plates. The rupture of this large strong contact causes great under-thrust earthquakes. In the rough surface region, large outer-rise earthquakes enhance the well-developed horst and grabens. As these structure are subducted with sediments in the graben part, the horsts create enough contact with the overriding block to cause an earthquake in the shallow part of the interface zone, and this earthquake is likely to be a tsunami earthquake. When the horst and graben structure is further subducted, many small strong contacts between the plates are formed, and they can cause only small underthrust earthquakes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73990/1/j.1440-1738.1997.tb00176.x.pd

Fault parameters and tsunami excitation of the May 13, 1993, Shumagin Islands earthquake

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95362/1/grl7531.pd

Frequency dispersion amplifies tsunamis caused by outer-rise normal faults

Although tsunamis are dispersive water waves, hazard maps for earthquake-generated tsunamis neglect dispersive effects because the spatial dimensions of tsunamis are much greater than the water depth, and dispersive effects are generally small. Furthermore, calculations that include non-dispersive effects tend to predict higher tsunamis than ones that include dispersive effects. Although non-dispersive models may overestimate the tsunami height, this conservative approach is acceptable in disaster management, where the goal is to save lives and protect property. However, we demonstrate that offshore frequency dispersion amplifies tsunamis caused by outer-rise earthquakes, which displace the ocean bottom downward in a narrow area, generating a dispersive short-wavelength and pulling-dominant (water withdrawn) tsunami. We compared observational evidence and calculations of tsunami for a 1933 Mw 8.3 outer-rise earthquake along the Japan Trench. Dispersive (Boussinesq) calculations predicted significant frequency dispersion in the 1933 tsunami. The dispersive tsunami deformation offshore produced tsunami inundation heights that were about 10% larger than those predicted by non-dispersive (long-wave) calculations. The dispersive tsunami calculations simulated the observed tsunami inundation heights better than did the non-dispersive tsunami calculations. Contrary to conventional practice, we conclude that dispersive calculations are essential when preparing deterministic hazard maps for outer-rise tsunamis