Annual Meeting - SCEC.org

Report | SCEC Research Accomplishments
Zhao, P., Z. Peng, Z. Shi, M. A. Lewis, and Y. Ben-Zion (2010), Variations of the velocity contrast and rupture properties of M6
earthquakes along the Parkfield section of the San Andreas Fault, Geophys. J. Int., 180, 765–780, doi:10.1111/j1365-
246X.2009.04436.x.
Crustal Deformation Modeling
The goal of the SCEC Crustal Deformation Modeling (CDM) focus group is gaining an understanding of how faults work
mechanically, during the interseismic interval and over geological time. This provides insights on absolute stresses and
stressing rates in the Earth’s crust (and along active faults in particular). We also use our deformation models to estimate fault
slip rates and other parameters from surface velocity data (e.g. the SCEC GPS velocity field), for the UCERF rupture
forecasting process. For 2010, forty SCEC proposals were flagged by the PI’s as fitting into the CDM Focus Area, though
perhaps half of these related directly to modeling static deformation of the Earth’s crust. Our activities for 2010 may be
divided loosely into four categories (there is some overlap): (i) conducting workshops, (ii) block and boundary-element
modeling, (iii) modeling long-term deformation (at the regional scale or within individual fault systems), and (iv) modeling
earthquake-cycle deformation. Developing earthquake simulators is a joint undertaking with EFP, so we will summarize just
the workshop here.
Figure 37. Second invariant of the 2D horizontal strain rate tensor, derived from GPS velocity measurements using a variety of approaches.
The original references may be found in the following URL: http://sceccore.usc.edu/proposalfiles/2010reports/Thatcher_10082_report.pdf. The
area shown here is limited to the union of the coverage of all 15 strain rate maps that were submitted by GPS-UCERF workshop participants.
For comparison purposes only, the area distribution of the earthquake probability P of the UCERF-2 earthquake forecast ("UCERF, bottom
right panel) was scaled into strain rate using the following ad-hoc formula: dε/dt = 10P + 3.4 . The 3.4 factor was selected so the variance on
the UCERF2 strain rate matched the median variance of the 15 strain rate maps. From David Sandwell.
68 | Southern California Earthquake Center