The uneven crustal structure at the subduction termination between Rivera and North American plates at the Jalisco block

Subduction Interface Processes Meeting (SIP), An International Conference Zooming On Subduction Zones, 19-21 April 2017, BarcelonaThe crustal structure of the western boundary of Mexico is strongly controlled by the Middle America Trench (MAT) which is the morphological expression of an active subduction zone involving the North American plate and the relatively young Rivera and Cocos plates, and it is the location of significant tectonics, widespread seismicity and magmatism. Here we show the results of multichannel seismic records, coincident with wide angle seismic profiles, acquired in the framework of the TsuJal project. We have identified in the MCS sections the collision zone between the Rivera and North American plates in the region of the Tres Marias Islands, which shows noteworthy differences from north to south. North of Tres Marias Islands there is no clear indication of an active subduction zone, while southwards between Maria Magdalena and Maria Cleofas Islands, we clearly observe the subducted slab of the Rivera plate with an incipient accretionary prism indicating near termination of the subduction zone. 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 mainlandPeer Reviewe