HR: 11:35h
AN: S12A-06    [Abstracts]
TI: Rupture Characteristics of the 2002 Denali Fault Earthquake from Surface Waves Observed at Regional Distances by 1-Hz GPS
AU: * Bodin, P
EM: pbodin@memphis.edu
AF: CERI, University of Memphis, Memphis, TN 38152 United States
AU: Bilich, A
EM: Andria.Bilich@colorado.edu
AF: Dept. of Aerospace Engineering Sciences, University of Colorado, Boulder, Boulder, CO 80309 United States
AU: Larson, K
EM: Kristine.Larson@colorado.edu
AF: Dept. of Aerospace Engineering Sciences, University of Colorado, Boulder, Boulder, CO 80309 United States
AU: Gomberg, J
EM: gomberg@usgs.gov
AF: US Geological Survey, University of Memphis, Memphis, TN 38152 United States
AU: Dragert, H
EM: hdragert@nrcan.gc.ca
AF: Pacific Geoscience Centre, Geological Survey of Canada, Sidney, BC V8L 4B2 Canada
AB: The 2002 Denali Fault earthquake, Mw=7.9, generated large surface waves throughout the western Cordillera of North America. The seismic radiation pattern and rupture directivity effects from the ~300 km long, shallow, and dominantly strike-slip rupture combined to produce large horizontal ground motions. Local and near-regional strong ground motion observations (although rather sparse) and more distant broadband recordings have led to models of the rupture process initiating with a small (M~6.5) dip-slip sub-event at the northwest end of the rupture, then propagating as nearly vertical strike-slip to the southeast and south-southeast. These previous studies have identified several areas of particularly intense slip and energy release, but differ in details and as to whether the velocity of rupture propagation may have exceeded the shear wave velocity at times. In this study we use 23 3-component 1-hz GPS displacement seismograms from western Canada and the Pacific Northwest, at epicentral distances from 700 to 2760 km to study the Denali source zone. At these distances broadband seismometer recordings are usually clipped, whereas the GPS surface wave displacement seismograms are on-scale but contain high noise levels relative to inertial seismograph data. We model the GPS displacement waveforms using locked mode traveling wave synthetics and published velocity models. To verify our Earth structure model we first match the velocity waveforms from the Mt. Nenana M6.7 earthquake recorded at regional broadband seismic stations. We have also studied the noise budget of the GPS observations in order to know what represents modelable signal. In our preliminary modeling results the initial dip-slip sub-event and the smaller strike slip sub-events are not seen in the GPS data. However, the large asperities and southeastward rupture propagation in the high-slip middle of the rupture are clearly revealed.
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1244 Standards and absolute measurements
DE: 7215 Earthquake source observations (1240)
DE: 7255 Surface waves and free oscillations
DE: 7294 Seismic instruments and networks (0935, 3025)
SC: Seismology [S]
MN: Fall Meeting 2005