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Poster Abstracts | Group 2 – FARM
2-102
INVERSION OF STRONG MOTION DATA FOR THE 2004 CHUETSU NIIGATA
EARTHQUAKE Masson J, and Archuleta RJ
The October 23, 2004, M 6.8 Chuetsu mid Niigata thrust earthquake occurred on a reactivated
normal fault. The hypocenter is at 37.307N, 138.839E and at a depth of 10.6 km. The fault strikes 212
degrees with a dip of 47 degrees. This earthquake was widely recorded by KiK-net, KNET and
JMA stations. Using the method of Liu and Archuleta (2004), we inverted 3-component bandpassed
(0.1–1.0 Hz) velocity time series from 20 stations that were well distributed in azimuth.
Because of known velocity changes, we used two different anelastic velocity structures for stations
to the northwest and southeast. We computed a suite of inversions. In general, we find that the
maximum slip (~2 m) occurs updip from the hypocenter with relatively small slip near the
hypocenter. The rupture velocity is between 2.5 km/s and 3.0 km/s. We also did a number of
different tests to examine the spatial resolution of the stations we were using. The results indicate
that the misfit in the data can grossly underestimate the resolution of the model. In our simple
models we checked for how well slip in the hypocentral region might be resolved. If slip were
concentrated at the hypocenter, the stations apparently would partly resolve the slip. However,
there are cases where the slip is more distributed in space that indicate the stations have relatively
poor resolution of the slip near the hypocenter. There are more stations that can be added that
might improve the resolution.
196 | Southern California Earthquake Center