I present a frequency-independent 3D seismic attenuation model (indicated by Q−1 P) for the crust of the Salton trough and the adjacent regions in southeastern southern California. The simul2000 tomographic algorithm was used to invert the frequency-independent attenuation operator t* values measured from amplitude spectra of 23,378 P-wave arrivals of 1203 events through a recently developed 3D velocity model. The QP model has a uniform horizontal grid spacing of 5 km, and the vertical-node intervals range between 2 and 5 km down to 27 km depth. In general, the QP values increase with depth and agree with the surface geology in the shallow depth layers. Low QP values are observed in the Imperial Valley, California, which are consistent with the sedimentary deposits and may also reflect the presence of pore fluid in the active fault zones, whereas greatly elevated QP values are shown in the surrounding crystalline ranges. The new QP model provides an important complement to the existing velocity models for interpreting structural heterogeneity and fluid saturation of rocks in the study area.
ASJC Scopus subject areas
- Geochemistry and Petrology