Depth of the Moho in northern Baja California using (Pg-Pn)travel times

Abstract

Mean Moho depths along the axis of the Peninsular Ranges in northern Baja California are obtained from refracted waves of events in northern Baja California recorded on an array of 9 broadband seismic stations across the northern Baja California Peninsula at about latitude 31°N. We used 35 events located with RESNOM (Red Sísmica del Noroeste de México) and RANM (Red de Acelerógrafos del Noroeste de México) local data. Focal depths range from 3 to 15 km and magnitudes from 2.1 to 3.9. A 1-D velocity model (Nava and Brune, 1982) was used to calculate theoretical travel times of Pg and Pn for different Moho depths. The differences between observed and theoretical (Pg-Pn) travel times was minimized in an iterative process in order to find the most likely Moho depth along the axis of the Peninsular Ranges between latitudes 31.3° and 31.7°N. It was found that the average Moho depth is approximately 42±3 km in the western Peninsular Ranges, diminishing to 31±3 toward the west along the Pacific Ocean and to 20±3 km toward the Gulf of California.