Shallow seismic structure of Mexico and vicinity from ambient noise tomography

Previous tomographic models for Mexico and surrounding regions based on surface waves have been obtained either for small local regions or are part of continental-scale or global studies. We present here the results of high-resolution Rayleigh and Love wave tomography for the entire Mexican territory and vicinity from correlations of seismic ambient noise. For this study we take advantage of the increasing number of broadband stations deployed in recent years in North and Central America. We use a total of 86 stations, including those of the National Seismological Service of Mexico (SSN), the USGS Caribbean network, and other permanent and temporary stations (e.g. USArray and PASSCAL experiments) available from the IRIS DMC, to obtain 30-month (2006-2008) stacked noise cross-correlations of vertical and horizontal component records. From these Green’s functions we measure fundamental-mode Rayleigh and Love wave group and phase velocities using the frequency-time analysis method (FTAN). We then invert these measurements to obtain group and phase velocity maps from 8 to 60 s period. Resolution is better than 200 km for most of the model region located inside the station distribution. The resulting images of Mexico’s crustal and upper mantle structure cover a considerably wider area than local studies and show higher resolution than continental or global models. Future inversion of the dispersion maps will produce a 3-D shear-wave model of the crust and upper mantle of Mexico and surroundings.