Crustal thickness estimates for Baja California, Sonora, and Sinaloa, Mexico, using disperse surface waves

Abstract

Dispersed surface waves of regional events recorded at Network of Autonomously Recording Seismographs (NARS)‐Baja and Red Sísmica de Banda Ancha (RESBAN) networks located over the Baja California Peninsula, Sonora, and Sinaloa, Mexico, were used to estimate shear wave elastic models and crustal thickness. We analyzed fundamental modes of surface waves with period between 10 and 40 s. Multiple filter analysis and the inversion method described by Herrmann and Ammon (2003) was used. Crustal thickness estimates for the Peninsular Ranges of Northern Baja California agree with those obtained by previous studies in the Peninsular Ranges of Northern Baja California. We analyzed dispersion of surface waves with northwest‐southeast travel paths along the east and west sides of the Baja California Peninsula as well as a northwest‐southeast travel path along the western sides of the Mexican states of Sonora and Sinaloa. It was found that the crustal structure east of the Baja California Peninsula is similar to the structure of Sonora and Sinaloa. The correlation between those two structures suggests dextral offset of the order of 275 ± 25 km if we consider Baja California Peninsula as a rigid body moving toward the northwest relative to the North America plate. This displacement between the structures is in agreement with the displacement determined by the dating of Miocene deposits located in San Felipe on the Baja California Peninsula (Pacific plate), and Isle Tiburon located west of Sonora (North America plate).