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Group 2 – Seismology | Poster Abstracts
broadband stations in California Integrated Seismic Network (CISN). Data were selected between
0.13-0.37 Hz for which S/N is high. In our analysis, ZH ratios show characteristic regional
behaviors, in particular for basins where ZH ratios show a minimum around 0.15-0.20 Hz. In fact,
this behavior of ZH ratio data helps discern whether a station is in a basin structure.
Phase velocity data were obtained from Green’s functions, generated by cross-correlations of
seismograms (hereafter correlograms). This data set in the frequency range, 0.13 to 0.20 Hz, is
sensitive to the upper 10-20 km, thus provides constraints on average S-wave velocity in the upper
crust. We used at least one-year to at most four-year length of CISN data. From pairs of about 140
stations, we selected about 1500 good S/N correlograms, which Rayleigh wave records, obtained
from vertical-vertical cross-correlations. Frequency range of 0.13 to 0.20 Hz was chosen where S/N
is high. This range could be extended slightly further but noise is high between 0.1 and 0.2 Hz for
Southern California. Thus, correlograms are analyzed within 0.13 to 0.20 Hz.
As the depth sensitivities of ZH ratios and phase velocity are complimentary, they can be inverted
simultaneously to resolve the entire upper crust. Our ultimate goal is to improve our predictive
capability of ground motions, in particular for urban areas which are typically in basin structures.
2008 SCEC Annual Meeting | 213