Imaging P and S attenuation in the Sacramento-San Joaquin Delta region, northern California

We obtain 3-D Qp and Qs models for the Delta region of the Sacramento and San Joaquin Rivers, a large fluvial-agricultural portion of the Great Valley located between the Sierra Nevada batholith and the San Francisco Bay - Coast Ranges region of active faulting. Path attenuation t* values have been obtained for P and S data from 124 distributed earthquakes, with a longer variable window for S based on the energy integral. We use frequency dependence of 0.5 consistent with other studies, and weakly favored by the t* S data. A regional initial model was obtained by solving for Q as a function of velocity. In the final model, the Great Valley basin has low Q with very low Q (