Source Parameters of the Shallow 2012 Brawley Earthquake, Imperial Valley
Resolving earthquake parameters, especially depth, is difficult for events occurring within basins because of issues involved with separating source properties from propagational path effects. Here, we demonstrate some advantages of using a combination of teleseismic and regional waveform data to improve resolution following a bootstrapping approach. Local SS‐S differential arrivals from a foreshock are used to determine a local layered model which can then be used to model teleseismic depth phases: pP, sP, and sS. Using the cut‐and‐paste (CAP) method for which all strike (θ), dip (δ), rake (λ), and depth variations are sampled for several crustal models. We find that regional data prove the most reliable at fixing the strike, whereas the depth is better constrained by teleseismic data. Weighted solutions indicate a nearly pure strike‐slip mechanism (θ=59°±1°) with a centroid depth of about 4.0 km and an M_w of 5.4 for the mainshock of the 2012 Brawley earthquake.
Additional Information© 2013 Seismological Society of America. Manuscript received 1 November 2012. We thank Associate Editor Cezar I. Trifu and an anonymous reviewer for the valuable comments that greatly improved the manuscript. We thank Egill Hauksson for providing his relocated earthquake hypocenters. This work is partially supported by the Gordon and Betty Moore Foundation through the Tectonics Observatory at California Institute of Technology. Additional support came from USGS through Award Number G12AP20072. This is Contribution Number 10084 of Seismological Laboratory, California Institute of Technology.
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