SCEC Award Number 14189 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Improving the density of GPS velocities in southern California by resurveying single occupation sites
Investigator(s)
Name Organization
Gareth Funning University of California, Riverside
Other Participants John Conrad (Graduate student), Michael Floyd (Collaborator)
SCEC Priorities 4a, 1a, 1d SCEC Groups Geodesy, SDOT, Transient Detection
Report Due Date 03/15/2015 Date Report Submitted N/A
Project Abstract
 GPS survey campaigns are a cost-effective way to increase the density of deformation velocities. In particular, ‘single occupation’ sites, locations that have only been surveyed (occupied) once with GPS equipment, are particularly appealing targets for such campaigns, as a single new occupation will yield a new velocity estimate. For this project, we targeted single occupation sites in three specific areas: (i) the Western Transverse Ranges, including the Ventura basin – a SCEC Special Fault Study Area that has limited existing GPS data coverage; (ii) the Elsinore fault, a structure capable of sustaining large earthquakes about which comparatively little is known; and (iii) the northern Mojave desert, where signatures of the Garlock fault and Eastern California Shear Zone may be measured. In all, we found 37 benchmarks and occupied 23 of them. Each occupation was for a minimum of eight hours. In total, nine new velocities were produced through our efforts, and 12 velocities were updated. Preliminary results of elastic dislocation modeling of the new velocity data in the Ventura Basin imply slip of 10-12 mm/yr on a 50° northward-dipping fault. The new data will be included in the GPS processing effort for the SCEC Community Geodetic Model.
Intellectual Merit GPS velocities permit the estimation of the rates of interseismic strain accumulation, and are therefore important inputs to seismic hazard assessments such as the Uniform California Earthquake Hazard Forecast (UCERF). In total, nine new GPS velocities were produced through our efforts, and 12 velocities were updated. Preliminary results of elastic dislocation modeling of the new velocity data in the Ventura Basin (A SCEC Special Fault Study Area) imply slip of 10-12 mm/yr on a 50° northward-dipping fault.
Broader Impacts The study involved the training of a SCEC/SURE summer intern, Lisa Jose, under the supervision of the PI and graduate student John Conrad. The new data will be included in the GPS processing effort for the SCEC Community Geodetic Model, an effort to produce a comprehensive, integrated geodetic data set that can be used by modelers and other nonspecialists.
Exemplary Figure Figure 4: Updated velocity information from the Ventura Basin area. Top: enlarged map showing new velocity estimates (red) with those from continuous sites (black). Bottom: preliminary results of elastic dislocation modeling of the new velocity data, showing that a layered elastic model can achieve a similar fit to a half space model, but require a lower slip rate.