Rupture process of the 2004 Parkfield earthquake from near-fault seismic waveform and geodetic records

Abstract

The 28 September 2004 Parkfield earthquake, arguably the best recorded earthquake even allows for detailed investigation of finite-source models and their resolution. We have developed finite-source models using GPS and interferometric synthetic aperture radar geodetic data and seismic strong motion waveform data (f ≤ 0.5 Hz) both independently and combined. The preferred model shows that the rupture is predominantly unilateral to the NW with a small component to the SE. Slip is concentrated into two primary patches, one near the hypocenter and the other between 10 and 23 km to the NW within a narrow depth range (5-13 km). The scalar seismic moment is 1.3 × 1018 N m (Mw 6.0), the overall rupture length is 23 km, the peak slip is 0.45 m, and the rupture velocity is 2.6 km/s. The average static stress drop obtained from the spatially distributed slip model is 2.3 MPa, and peak values are 10 MPa. A detailed sensitivity and resolution analysis shows that the recovered slip, the average rupture velocity, risetime, and slip velocity are well resolved. Copyright 2008 by the American Geophysical Union.