Three-dimensional compressional wave attenuation tomography for the crust and uppermost mantle of Northern and central California

I present a frequency-independent three-dimensional (3-D) compressional wave attenuation model (indicated by quality factor Q(p)) for the crust and uppermost mantle of Northern and central California. The tomographic inversion used t* values measured from amplitude spectra of 80,988 P wave arrivals of 3247 events recorded by 463 network stations through a 3-D seismic velocity model. The model has a uniform horizontal grid spacing of 15 km, and the vertical node intervals range between 2 and 10 km down to 45 km depth. In general, the resulting Q(p) values increase with depth and agree with the surface geology at shallow depth layers. The most significant features observed in the Q(p) model are the high Q(p) values in the Sierra Nevada mountains and low Q(p) anomalies in the western fault zones. Low Q(p) values are also imaged in Owens Valley and Long Valley at shallow depths and the Cape Mendocino region in the lower crust (similar to 25 km depth). An overall contrast of Q(p) values across the fault is observed in the creeping, Parkfield and Cholame-Carrizo sections of the San Andreas Fault. The new 3-D Q(p) model provides an important complement to the existing regional-scale velocity models for interpreting structural heterogeneity and fluid saturation of rocks in the study area.