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The Jalisco region of western Mexico is the locus of interaction among the North America, Cocos, and Rivera plates, giving rise to the Jalisco block. This region is one of the most tectonically active in Mexico, and here took place the largest instrumentally recorded earthquake in Mexico the twentieth century, on 3 June 1932 (M 8.2), three important tsunamis in the last 100 yrs, and two of the most active volcanoes in Mexico. Nevertheless, the first seismicity studies here, undertaken with temporary networks, did not commence until 1994. In 2008, the Government of Jalisco and the University of Guadalajara funded a research project to install a seismic network in this region. The principal objective was to study the seismic hazard in the region and characterize seismic parameters in the different areas to design building codes. The Red Sísmica y Acelerométrica Telemétrica de Jalisco (RESAJ) project was thus initiated in 2009. Its Central Lab is at Centro de Sismología y Volcanología de Occidente (SisVOc), located at the Universidad de Guadalajara in Puerto Vallarta. Currently, the RESAJ has 26 telemetered and 2 autonomous stations. The RESAJ serves as the seismological lab for the postgraduate program at SisVOc.

Processing and analysis of new multichannel seismic records, coincident with wide-angle seismic profiles, acquired in the framework of the TsuJal project allow us to investigate in detail the complex structure of the oceanic domain in the collision zone between Rivera Plate and Block Jalisco at its northern termination. The subducting Rivera Plate, which is overridden by the North American Plate-Jalisco Block, is clearly identified up to 21.5°N (just south of Maria Magdalena Island) as a two clear reflections that we interpret as the interplate and Moho discontinuities. North of the Tres Marias Islands the seismic images display a different tectonic scenario with structures that are consistent with large faulting and rifted margin. A two-dimensional velocity approach for the crustal geometry is achieved using joint refraction/reflection travel time tomography, the uncertainty of the results is assessed by means of Monte Carlo analysis. Our results show an average oceanic crustal thickness of 6-7 km with a moderate increase towards the Jalisco Block, an anomalous thick layers (*3.0 km) displaying a relatively low velocity (*5.5 km/s) underneath Maria Magdalena Rise, and an estimated Moho depth deeper than 15 km in the collision zone between Rivera Plate and Jalisco Block. We have also determined an anomalous crust on the western flank of the Tres Marias Islands, which may be related to the initial phases of continental breakup of the Baja California Peninsula and Mexico mainland. High-resolution bathymetry provides remarkable images of intensive slope instabilities marked by relatively large slides scars of more than 40 km 2 extent, and mass-wasting deposits probably triggered by the intense seismicity in the area.