05/06/2016 - 3:30pm
Please join us for the GP Seminar
Friday, May 6, 3:30 pm
IGPP Conference Room (Munk 303)
(Coffee and snacks at 3:00 pm in the Reading Room!)
Is there a "blind" strike-slip fault at the southern end of the San Jacinto Fault system?
The San Jacinto Fault Zone has been recognized as an important part of the San Andreas Fault system, accommodating a significant portion of the plate-boundary slip, and representing a considerable seismic hazard. At its southern end, the Coyote Creek fault is currently believed to be the main strand of the San Jacinto fault system. However, geodetic and geologic studies have identified anomalous deformation to the east of the Coyote Creek fault, indicating the possibility of a “blind” continuation of the Clark Fault, which was previously believed to end at the Santa Rosa mountains. We present a study of this area using a combination of geodetic measurements from InSAR and GPS.
We have developed a method to reduce the errors due to the atmospheric noise in InSAR data, allowing for greater accuracy in investigating low-amplitude interseismic deformation. We have applied our method to the study of the deformation at the southern end of the San Jacinto Fault system, using a combination of ascending and descending InSAR tracks collected between the years 2003 and 2010 by the European satellite ENVISAT. We combined average velocities from different look angles to isolate the fault-parallel velocity field, and used fault-parallel velocities to compute strain rate. We filtered the data over a range of wavelengths prior to numerical differentiation, to reduce the effects of noise and to investigate both shallow and deep sources of deformation. We observe strain rate anomalies east of the Coyote Creek Fault at both long and short wavelengths, likely corresponding to deep and shallow creep on a “blind” continuation of the Clark Fault that accommodates a significant portion of the deformation on the southern end of the San Jacinto.
To complement the InSAR data, we have used measurements of continuous GPS velocities from the PBO network. In addition, we have conducted four campaign-style GPS surveys of 19 benchmarks along Highway 78, and processed the campaign data using GAMIT to obtain horizontal velocities. The GPS data show high velocity gradients to the east of the Coyote Creek fault, in good agreement with the results from InSAR.
For more information on this event, contact:
8610 Kennel Way La Jolla, CA 92037, US