Local earthquake reflection tomography of the Landers aftershock area

A detailed tomographic image of the crust in the 1992 Landers earthquake (M 7.3) region in southern California is determined by using the first arriving S-waves and the reflected S-waves from the Moho discontinuity (SmS, sSmS) generated by the Landers aftershocks. These data were recorded by two seismic stations that are separated by about 200 km. The tomographic image obtained has a lateral resolution of 25–35 km (1 / 6 to 1 / 8 of the station spacing). This work indicates that crustal reflected waves are very useful to improve the spatial resolution of crustal tomography. Our results show a tendency for areas rich in seismicity to be associated with higher velocities, suggesting that earthquake occurrence is closely related to the in situ structural heterogeneities of the fault zone.