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 ever, 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.