HR: 0800h
AN: G51C-0848    [Abstracts]
TI: A Fault Model of the 1993 Klamath Falls Earthquakes Estimated From SAR Interferometry
AU: * Yarai, H
EM: hyarai@usgs.gov
AF: Geographical Survey Institute of Japan, Kitasato 1, Tsukuba, 305-0811 Japan
AU: * Yarai, H
EM: hyarai@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AU: Wicks, C
EM: cwicks@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AB: Two M6 class normal fault earthquakes struck near Klamath Falls, Oregon, on September 20, 1993. Many mapped normal faults exist in the Klamath Falls area, but no surface ruptures related to the earthquakes were found. There are no existing traditional geodetic measurements of displacement derived from the earthquakes, so we have estimated source parameters for the earthquakes through InSAR data. Interferograms of the Klamath Falls area were generated from European Space Agency ERS-1 and ERS-2 satellite data. In addition, for more efficient modeling, we applied quad-tree partitioning to reduce the number of interferogram data points. At first, we assumed a uniform slip fault in homogeneous and isotropic elastic half-space. Our estimated fault model parameters are 13km length, 11km width, 3.5km depth (to the top of the fault), and a strike and dip of 332° and 49° (east dipping), respectively. These values of strike and dip are consistent with CMT solutions (eg. Braunmiller et al, 1995). The estimated down dip slip is 0.34m. The moment derived from estimated fault parameters is 1.5*10¹⁸ Nm (Mw6.1) and it is equal to about 70% of the sum of moments of the two main shocks derived from CMT solutions. The stress drop calculated from the fault parameters is 0.8MPa, which is smaller than usual intraplate earthquakes. A more detailed study of the Klamath Falls earthquakes is needed and additional constraints on models should be provided using ascending satellite data.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1243 Space geodetic surveys
DE: 6924 Interferometry (1207, 1209, 1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Geodesy [G]
MN: Fall Meeting 2005