GPS source solution of the 2004 Parkfield earthquake

TL;DR

This study uses 1 Hz GPS data to analyze the 2004 Parkfield earthquake's fault slip, confirming shallow slip contributions, GPS saturation effects, and consistency with strong motion data, providing detailed rupture models.

Contribution

It introduces a GPS-based finite-source inversion method that accurately estimates slip distribution even with GPS station limitations.

Findings

GPS waveforms constrain slip at depth without stations directly above rupture.

GPS saturation occurs near the fault but still allows velocity estimation.

Slip amplitudes are around 55 cm with rupture velocities of 2-5 km/s.

Abstract

We compute a series of finite-source parameter inversions of the fault rupture of the 2004 Parkfield earthquake based on 1 Hz GPS records only. We confirm that some of the co-seismic slip at shallow depth (<5 km) constrained by InSAR data processing results from early post-seismic deformation. We also show 1) that if located very close to the rupture, a GPS receiver can saturate while it remains possible to estimate the ground velocity (~1.2 m/s) near the fault, 2) that GPS waveforms inversions constrain that the slip distribution at depth even when GPS monuments are not located directly above the ruptured areas and 3) the slip distribution at depth from our best models agree with that recovered from strong motion data. The 95th percentile of the slip amplitudes for rupture velocities ranging from 2 to 5 km/s is, 55 +/- 6 cm.