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GEOPHYSICAL RESEARCH LETTERS,
VOL. 32,
L08305,
doi:10.1029/2004GL022320,
2005
Contiguous rupture areas of two Nankai Trough earthquakes revealed by high-resolution tsunami waveform inversion
Toshitaka Baba
Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
Phil R. Cummins
Minerals and Geohazards Division, Geoscience Australia, Canberra, A. C. T., Australia
Abstract
We have developed a new method for inverting tsunami waveforms that reveals considerable detail in megathrust slip during
subduction zone earthquakes. Previous methods have ensured compliance with the shallow-water theory used to compute tsunami
waveforms by using large subfaults that generate only long-wavelength seafloor deformation. We show that a better approach
is to use small subfaults coupled with a smoothing criterion that ensures compliance with the shallow-water approximation.
In an application of the method to historical earthquakes in the Nankai Trough, southwestern Japan, we find that the areas
with slip > 1 m for the earthquakes of 1944 and 1946, which ruptured adjacent segments of the subduction zone, are separated
by a sharp, non-overlapping boundary. This establishes that interseismic accumulation of strain energy extends very close
to the boundary between rupture zones, and strongly suggests that this boundary is associated with a physical barrier to rupture.
Received 27
December
2004;
accepted 22
March
2005;
published 19
April
2005.
Index Terms: 4564 Oceanography: Physical: Tsunamis and storm surges; 7209 Seismology: Earthquake dynamics (1242); 7240 Seismology: Subduction zones (1207, 1219, 1240).
Read Full Article (file size: 517785 bytes) Cited by
Citation: Baba, T., and P. R. Cummins
(2005),
Contiguous rupture areas of two Nankai Trough earthquakes revealed by high-resolution tsunami waveform inversion,
Geophys. Res. Lett.,
32,
L08305,
doi:10.1029/2004GL022320.
Copyright 2005 by the American Geophysical Union.
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