INVERSION FOR THE VELOCITY STRUCTURE OF THE SANTA CLARA VALLEY, CALIFORNIA

In our previous work we investigated teleseismic, local, and microseism data recorded by the 41-station seismic array in the Santa Clara Valley (SCV). We have found strong correlations between basin depth reported in the USGS 3D seismic velocity model (ver. 2) and different relative measures of ground motion parameters such as teleseismic arrival delays, P-wave amplitudes, wave energy, local earthquake S-wave amplitudes, and periods of microseism horizontal to vertical spectral ratio peaks. The teleseismic, local earthquake, and microseism observations were also found to be strongly correlated with one another. The results suggested that all three datasets are sensitive to the basin structure and could therefore be used to improve the 3D velocity model.

We started to develop a simultaneous inversion of the teleseismic, local, and microseism observations to refine the present seismic velocity model. We use a 3D elastic finite-difference code to simulate the teleseismic, local, and microseism wavefields. The inversions are performed in the 0.1 to 1.0 Hz passband in which the SCV seismic experiment observations had a good signal to noise ratio. We will present preliminary results that invert for the velocity structure within the basins, while the basin geometry as defined in the USGS velocity model is held fixed.