This electronic supplement includes tables of the locations and focal mechanisms for the earthquakes of the California Central Coast, and the seismic velocity model used to improve the absolute earthquake locations and focal mechanisms. It also includes validation of the location procedures, in the form of earthquake catalogs from each step of the relocation process, and checkerboard tests to validate the velocity model.
Table S1. Relocated earthquake catalog, shown in Figure 8 of the paper. Earthquakes inside the San Simeon aftershocks zone are relocated using the 3D velocity model of McLaren et al. [2008], and the relative locations refined using hypoDD [Waldhauser and Ellsworth, 2000]. Earthquakes inside the San Luis Obispo subregion are relocated using tomoDD [Zhang and Thurber, 2003]. Earthquakes outside of the two subregions are relocated using the regional 3D velocity model and refined using hypoDD. All relocations utilize waveform cross-correlation relative arrival times. Catalog is in standard hypoDD format, file has one header line giving the format.
Table S2. Single event focal mechanisms, shown in Figure 10 of the paper. Quality A-C as defined by Hardebeck and Shearer [2002]. Quality D are more poorly-constrained events deemed acceptable by inspection. Catalog in standard HASH [Hardebeck and Shearer, 2002] format, file has one header line giving the format.
Table S3. Composite focal mechanisms, shown in map view in Figure 11 of the paper. Location given is the average location of events used to form the composite. Quality A-C as defined by Hardebeck and Shearer [2002]. Quality D are more poorly-constrained events deemed acceptable by inspection. Catalog in standard HASH format, file has one header line giving the format.
Figure S1. Relocations with best 1D model, events shown are those with RMS < 0.3 sec.
Figure S2. Relocations in the regional 3D model, events shown are those with RMS < 0.1 sec.
Figure S3. Relocations in regional 3D model, then relative locations refined with hypoDD. Events shown are those with RMS < 0.3 sec for both absolute travel times and relative travel times (with the exception of the Queenie Structure cluster.)
Figure S4. First-motion plots for composite focal mechanisms, from Table S3 and shown in map view in Figure 11 of the paper. Red: first-motion up; Blue: first-motion down.
Table S4. Vp model, shown in Figure 6 of the paper. The model of McLaren et al. [2008] is given inside the San Simeon aftershocks zone, the San Luis Obispo tomoDD model is given inside the San Luis Obispo subregion, and the regional model is given everywhere outside of the two subregions. Format: lon lat depth Vp.
Table S5. Vs model, shown in Figure 7 of the paper. The model of McLaren et al. [2008] is given inside the San Simeon aftershocks zone, the San Luis Obispo tomoDD model is given inside the San Luis Obispo subregion, and the regional model is given everywhere outside of the two subregions. Format: lon lat depth Vs.
Figure S5. Results of a checkerboard test of the resolving power of the Vp model. The "true" model is the average 1D model with perturbations of ±5% in alternating 25 km by 25 km squares. The synthetic arrival time dataset was generating using ray-tracing through this "true" model and the source-station geometry of the real dataset. The inversion was carried out exactly as the inversion of the real arrival time data. The accuracy of the model is much better in the on-shore and near-shore regions, and is completely unresolved west of the Hosgri Fault. The resolution is best in the depth range of 4-8 km, and is best in the northern half of the model area. There is a little smearing, mainly in the NE-SW direction. In general, the "true" model is reproduced with reasonable accuracy where ray-coverage is adequate to constrain the velocity structure, while the starting model is retained where it is not (white areas.)
Figure S6. Results of a checkerboard test of the resolving power of the Vp/Vs model, as in Figure S5. The results are troubling, in that the Vp/Vs ratio is poorly resolved over most of the region, and instead of reverting to the starting model (white), the model Vp/Vs ratio is uniformly ~5% too high through the center of the model and ~2% too low elsewhere. The Vp/Vs model only appears to be at all reliable in the 4-10 km depth range in a strip along the coast between San Simeon and Point Buchon. The majority of S-wave picks are from CCSN stations along the coast.
Hardebeck, J. L. and P. M. Shearer (2002). A new method for determining first-motion focal mechanisms, Bull. Seism. Soc. Am., 92, 2264-2276.
McLaren, M. K., J. L. Hardebeck, N. van der Elst, J. Unruh, G. W. Bawden, J. L. Blair (2008). Complex faulting associated with the 22 December 2003 Mw6.5 San Simeon, California earthquake, aftershocks and postseismic deformation, Bull. Seism. Soc. Am. 98, 1659-1680.
Waldhauser, F. and Ellsworth, W. L. (2000). A double-difference earthquake location algorithm; method and application to the northern Hayward Fault, California, Bull. Seism. Soc. Am., 90, 1353-1368.
Zhang, H., and C. H. Thurber (2003). Double-difference tomography: the method and its application to the Hayward fault, California, Bull. Seism. Soc. Am., 93, 1875-1889.
