Surface wave tomography of the Gulf of California

We measured interstation fundamental mode Rayleigh wave phase velocities using data from the NARS‐Baja seismic network located around the Gulf of California. A region‐average, shear velocity model and a set of azimuthally anisotropic phase velocity maps are obtained from these data. The average shear velocity structure shows a strong low‐velocity zone underlying a thin lid and the data are suggestive of low velocities down into the transition zone. The phase velocity maps display signatures of sedimentary layers, crustal thickness variations, upwelling under the plate boundary, and the presence of the subducted Farallon microplate remnants beneath the Gulf. The upper mantle features inferred from this study provide new seismic evidence on the tectonic evolution of the region.