A comparative analysis of deformable layer tomography and cell tomography along the LARSE lines in southern California

Abstract

S U M M A R YWe 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.

A detailed image of the continent-borderland transition beneath Long Beach, California

“…The 1994 onshoreoffshore Los Angeles Region Seismic Experiment (LARSE) seismic survey gave an indication of this dip, but could not locate it accurately (Godfrey et al 2002;Nazareth and Clayton 2003). There have been regional-scale models (Richards-Dinger and Shearer 1997;Zhou et al 2010) that cross through the Long Beach area, but they lack the resolution to reveal the structure presented here. The Southern California Earthquake Center (SCEC) has developed two velocity models -CVM-H15 (Shaw et al 2015) and CVM-S4.26 (Lee et al 2014)-but these also do not have the structural detail presented here.…”

On the layering artifacts in seismic imageries

“…However, both methods produce de-mean artifact, and in this figure the finite-frequency solution appears to have more de-mean artifact than the ray-theoretical solution. Figure 10 shows another comparison between two methods, the deformable layer tomography (DLT) and the traditional cell tomography using the same data in a crustal study in California (Zhou et al, 2010). The DLT profile exhibits much better depth resolution and a higher level of geological plausibility than cell tomography because DLT directly inverts for the depths of velocity interfaces.…”

“…Unfortunately, most of the resolution tests are on the lateral velocity variations, and there is a lack of verification on the absolute velocity model. Figure 9 shows a checkerboard resolution test for a crustal study in California (Zhou et al, 2010). In additional to assess the lateral velocity variations in the checkerboard pattern, the resolvability for the layer average velocities was also evaluated.…”

Crustal and upper-mantle seismic reflectors beneath the Three Gorges Reservoir region

“…To overcome this obstacle, we applied a recently developed deformable layer tomography (DLT) method that is able to invert for the geometry of velocity interfaces directly (Zhou, 2006). The DLT method is more advantageous than the traditional cell tomography in crustal applications (Zhou et al, 2010). In this study, we apply the DLT along a west-east corridor which overlaps with the position of the seismic waveform profiles in Fig.…”