SCEC Award Number 12204 View PDF
Proposal Category Individual Proposal (Data Gathering and Products)
Proposal Title Postseismic deformation following the 2010 Sierra El Mayor-Cucapah earthquake measured using campaign GPS
Investigator(s)
Name Organization
Gareth Funning University of California, Riverside
Other Participants Floyd, Michael
Undergraduate student (TBA)
SCEC Priorities 1b, 1d, 1e SCEC Groups Geodesy, SDOT
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
 Ongoing GPS campaign surveys in the epicentral region of the El Mayor-Cucapah earthquake have highlighted several postseismic deformation processes. Horizontal component time series of the processed campaign data show a prominent component of right-lateral shear in the near-field of the earthquake, consistent with afterslip on an extension of the fault system responsible for the event, decaying with a characteristic time scale Joint inversions of these GPS data with the available InSAR data from the first five months following the mainshock show that the observed displacements can be explained by a combination of afterslip and fault-normal contraction. The longer term deformations, as measured by farther-field sites on the west side of Laguna Salada, require another deformation mechanism, most likely viscoelastic relaxation in the lower crust and upper mantle.
Intellectual Merit Our observations and results place constraints on the rheologic and frictional properties of the El Mayor-Cucapah fault system and the rocks that surround it. Postseismic deformation studies are one of the few means available to us to constrain these properties, which control how the lithosphere responds to stress.
Broader Impacts The processes and conditions identified here can be treated as an analogy for the plate boundary fault system in comparable geological conditions in the Salton Trough region of southern California. Our results will therefore inform models of earthquake recurrence and seismic hazard that in term inform estimates of seismic risk in southern California. This project also has helped foster collaboration between groups of researchers in the US and Mexico.
Exemplary Figure Figure 2: Horizontal component time series for selected campaign GPS sites in the near field of the El Mayor-Cucapah earthquake. Sites MXCT, LASA and PUAS are located to the southwest of the rupture, LPUR is located to the northeast of the rupture. Overall, the relative sense of motion is of right-lateral shear, consistent with afterslip. Best-fitting exponential, logarithmic and hyperbolic cotangent fits to the time series are represented by dashed, dotted and solid red lines, respectively; characteristic relaxation times (𝜏) are also included. From Gonzalez-Ortega et al. (2014).
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