This article summarizes a passive surface-wave method that uses only two sensors and its application to the estimation of deep S-wave velocity structure.
Three-dimensional S-wave velocity structure to a depth of several kilometers has a large effect on long-period ground motion in tectonic basins, such as the Los Angeles (LA) Basin. Recent studies of long-period ground motion in the LA Basin (e.g., Hatayama and Kalkan, 2012) show that observed ground motion in some areas cannot be explained by the S-wave velocity models in current use. Most studies of basin velocity structure rely on geologic information, surface and borehole geophysical data, and observed earthquake records to deduce or measure seismic velocities. Geophysical data and seismic stations commonly used for velocity analysis are sparsely distributed and most well data are too shallow to characterize deep S-wave velocity structure. To establish more accurate basin velocity structure, there is a need for more densely distributed deep S-wave velocity data.