The hypocenter is shown in the lower right of the image and the recording station (DLA) is located at the upper left end of the banana-shaped kernel. Local contribution to the observed travel time anomaly is the product of the local seismic wavespeed perturbation and the amplitude seen here.
Frechet kernels such as this can be used to improve the seismic wavespeed model around the Los Angeles Basin. Studies in the past have assumed that the sensitivities are only concentrated on the geometrical ray paths. The results shown here were calculated on the USC HPCC system using a finite-difference method together with a three-dimensional seismic wavespeed reference model for Southern California (SCEC Community Velocity Model 3.0).
The image was produced using Grid Visualization Toolkit developed at USC's ISI Center for Grid Technology.