Abstract
This study focuses on the shallow deformation that occurred during the 5 years following the Parkfield earthquake (28/09/2004, Mw 6, San Andreas Fault, California). We use Synthetic Aperture Radar interferometry (InSAR) to provide precise measurements of transient deformations after the Parkfield earthquake between 2005 and 2010. We propose a method to combine both ERS2 and ENVISAT interferograms to increase the temporal data sampling. Firstly, we combine 5 years of available Synthetic Aperture Radar (SAR) acquisitions including both ERS-2 and Envisat. Secondly, we stack selected interferograms (both from ERS2 and Envisat) for measuring the temporal evolution of the ground velocities at given time intervals. Thanks to its high spatial resolution, InSAR could provide new insights on the surface fault motion behavior over the 5 years following the Parkfield earthquake. As a complement to previous studies in this area, our results suggest that shallow transient deformations affected the Creeping-Parkfield-Cholame sections of the San Andreas Fault after the 2004 Mw6 Parkfield earthquake.
Highlights
During the time period from 1992–2004, the creep rate spatially decreased along the SAF: from about 2 cm/yr at the Creeping section, to 1.4 ± 0.3 cm/yr at the Northwestern Parkfield section, to 0.6 ± 0.3 cm/yr at the southeastern Parkfield section, and to ~0 cm/yr at the Cholame-Carrizo section[2,3,11]
We highlight that some sub-period stacks are more affected by atmospheric bias and noise because they are constructed from a lower number of interferograms
By combining ERS2 and Envisat interferograms, we could improve the spatio-temporal sampling of the surface creep evolution for the Creeping-Parkfield-Cholame sections of the SAF, between 2005 and 2010
Summary
During the time period from 1992–2004, the creep rate spatially decreased along the SAF: from about 2 cm/yr at the Creeping section, to 1.4 ± 0.3 cm/yr at the Northwestern Parkfield section, to 0.6 ± 0.3 cm/yr at the southeastern Parkfield section, and to ~0 cm/yr at the Cholame-Carrizo section[2,3,11]. Two–colored electronic distance meters and InSAR time series analysis have revealed a temporal change of the creep rate along the Parkfield section during the same time period (notably an episodic creep acceleration between 1999 and 2000 at the location of the PKEQ epicenter[11]). The PKEQ has triggered non-volcanic tremors (NVTs, Fig. 1) at the transition between the Parkfield and Cholame sections[17,18,19], which are associated with slow slip events occurring at 20 km depth[17], or viscoelastic relaxation of the lower crust in response to the PKEQ18 These studies show that the PKEQ induced long-term perturbations of crustal properties in the SAF zone at depth[17,18,19,20]. In complement to previous studies in this area, here we intend to better characterize the spatio-temporal distribution of the shallow fault displacement field after the PKEQ between 2005 and 2010
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
