Electronic Supplement to
Source Parameters of the Shallow 2012 Brawley Earthquake, Imperial Valley

by Risheng Chu and Don V. Helmberger

This supplement includes 4 figures. The first figure shows some examples of waveform fits for regional CAP inversion using velocity model SC. The second figure shows the comparison of synthetic teleseismic waveforms for a basin structure near the earthquake using different grid sizes in the FD calculation. The effect of soft sediment on teleseismic Green's functions is illustrated in the third figure. The last figure demonstrates the sensitivity of regional and teleseismic data on the focal mechanisms.

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Figures

Figure S1. Regional Cut-and-Paste inversion of the Brawley earthquake. The waveforms are arranged according to their azimuths. The P_nl and surface waves are filtered using corner frequencies of 0.02-0.2 Hz and 0.01-0.05 Hz, respectively. The station names are given on the right along with the distance in km. The best-fit mechanism is a strike-slip faulting at the depth of 5.5 km. The velocity model used here is SC. Observed and synthetic displacement waveforms are shown as black and red trace, respectively. The two numbers beneath each trace are its time shift relative to the synthetic segments generated from the 1D model to match the data and the cross-correlation coefficient. Note the low amplitude in the P nodal direction (WUAZ), and S nodal direction (IRM).

Figure S2. Synthetic teleseismic SH waveforms for a 2D basin structure using the 2D finite-difference algorithm. The velocity model is displayed in Figure 4. The red and black seismograms are for grid sizes of 1.0 km and 0.2 km, respectively.

Figure S3. Synthetic P-wave Green's functions for a strike-slip earthquake using velocity models SC (top), IV (middle), and ST (bottom). The station has a distance of 30°. The arrows indicate the direct P and the depth phases pP and sP. The calculations have different depths (numbers after the model names) to ensure the similar sP-P arrival times. The t^* for P and SH waves are 0.8 and 3.2 s, respectively [Chu et al., 2012].

Figure S4. Sensitivity of regional and teleseismic data on focal mechanisms. Comparison of synthetic (red) and observed data (black) for (A) regional Love waves and (B) teleseismic SH waves. For each dataset, synthetic waveforms are calculated using focal mechanisms from regional CAP solution (58/87/-7, left) and teleseismic CAP solution (59/90/1, right).

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