Project Abstract
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The work performed was to extract from continuous and survey-mode GPS timeseries the linear velocities at the sites along with parameters that describe co-seismic slip and afterslip of recent earthquakes (1992-2014). The time series from 550 sites in the CMM4 velocity field (Shen et al., 2011), from ~800 PBO sites and from ~300 sites from the Pacific Northwest velocity field (McCaffrey et al. 2013) were inverted simultaneously to estimate the source parameters for 13 earthquakes and afterslip for 10 of them. The linear velocities estimated were then used in a block model for California and vicinity to estimate slip rates on faults and to test whether or not the method used improves the agreement of the geodetic velocities with the geological slip rates. When the predicted fault slip rates at 13 well-determined locations are constrained to be within 1 mm/yr of the geologic rate, the new CMM4 survey-mode velocities give a normalized rms (Nrms) misfit of about 10% better for the same model and constraints. The improvement may be due to the longer time series providing better representations of the afterslip than was available for the original CMM4 estimates but other factors are likely involved. Eleven of the 13 geologic slip rates agree with the geodetic rates when the geologic rates are allowed to vary by 5 mm/yr. |
