Geodetic observations of the 2004 Parkfield earthquake and associated slip on the creeping section of the San Andreas

Offsets of five campaign sites (0508 05QJ SHAD 0510 05SK) between June, 2004 and Sep. 30 - Oct. 3, 2004 relative to continuous station VNDP (Vandenburg). Offsets for continuous sites (PKDB LOWS CRBT) as pseudo-campaign measurements are shown for reference. Campaign sites 05SH and 05RH did not have observations during June 2004, but were observed immediatly after the Parkfield earthquake.

Project Summary The Parkfield segment of the San Andreas is bounded on the north by the ³creeping section²; a freely slipping fault segment, which terminates near the town of San Juan Bautista. The creeping section is highly sensitive to input stresses, as evidenced by the transient slip events associated with the 1989 Loma Prieta and the 2003 San Simeon earthquakes. We investigate whether the Parkfield earthquake was similarly accompanied by transient slip in the creeping section. We present observations from GPS and InSAR of the 2004 Parkfield earthquake and associated slip on the San Andreas creeping section. In January 2003, we began surveying several sites near the San Andreas fault creeping section. They were re-surveyed immediately after the 2003 San Simeon earthquake, and then again in June of 2004. Following the Parkfield earthquake, seven benchmarks were re-occupied within 48 hours of the event. All sites were north of the rupture and experienced between 0 - 20 mm of coseismic offset. In addition to these campaign observations, we plan to incorporate continuous and campaign GPS data from other networks, as available. We will further supplement the GPS with high spatial resolution InSAR data. The European Space Agency satellite ENVISAT acquired data on an ascending track over Parkfield just two days after the earthquake. A descending track scene was acquired after eight days. There are a handful of pre-earthquake scenes, so the likelihood is good that a suitable interferometric pair can be found. We perform a joint inversion of GPS and InSAR data for slip on dislocations in an elastic half-space model. We present results for coseismic slip on the rupture plane and associated aseismic slip within the creeping section.
2004 AGU Fall Meeting abstract #10920

Tools Global Positioning Satellites (GPS)
Interferometric Synthetic Aperture Radar (InSAR)

Geographic Location Central California

Group Members Involved Ingrid Johanson <Email> <Personal Web Site>
Frederique Rolandone, Dennise Templeton, Roland Bürgmann


Data Access For access to the rinex files used in this project before the 2004 AGU meeting, please email Ingrid at the address above. All data will be archived with UNAVCO.


7/3/2003 - 9/30/2004 with fault traces overlaid

7/3/2003 - 9/30/2004 with Parkfield aftershocks and San Simeon model fault plane.