干旱区生态环境知识资源中心

We conducted a comparative analysis of the new deformable layer tomography (DLT) with the traditional fixed-in-space cell tomography along three 2-D crustal profiles of P-wave velocities in southern California using first arrivals from local earthquakes and two Los Angeles Regional Seismic Experiment (LARSE) seismic lines. The DLT method inverts for the depth-varying geometry of velocity interfaces, which include major velocity discontinuities near the top and bottom of the crust and boundaries between velocity layers in the middle crust. In regions characterized by large lateral velocity changes, the DLT method may improve the depth resolution of major velocity interfaces compared to traditional cell tomography using fixed-in-space cells or grids. We also tested the use of crustal thickness estimates from a receiver function study for constraining the depth range of the Moho geometry. Tests indicate that, in areas of sufficient ray coverage, the depth resolution of the DLT for major velocity interfaces is usually less than 1 km in the upper crust and less than 3 km in the lower crust. Our 2-D DLT models fit the first arrival data significantly better than three published 3-D cell tomography models along the profiles. The configurations of basin edges and undulating velocity discontinuities are well delineated in the DLT models and indicative of the crustal architecture of the region.