Crustal architecture at the collision zone between Rivera and Cocos Plates with North American Plate at the Western Margin of Mexico TSUJAL PROJECT
Crustal architecture at the collision zone between Rivera and Cocos Plates with North American Plate at the Western Margin of Mexico TSUJAL PROJECT
Previously Published Material: Preliminary data were submitted to the AGU fall meeting in 2014
Abstract ID#: 34925
English Abstract:
During the spring of 2014, within the framework of TSUJAL project, Spanish and Mexican scientists investigated the western margin of Mexico at the collision zone between Rivera, Cocos and North American plates. The main objective was to define the crustal architecture of this active margin and recognize potential structural sources that can trigger earthquakes and tsunamis at the convergence between Rivera plate-Jalisco block with the North American Plate. To achieve these goals a wide-ranging of geophysical data were acquired aboard the RSS James Cook. Stacked MCS seismic sections show a well-developed deformation front of the accretionary wedge that can be traced northwards till the two southern Marias Islands. The contact between the Rivera and NA Plates is observed as a strong reflection at 6 s two way travel time (TWTT), in a parallel offshore profile (TS01), south of Manzanillo. This contact is also identified in a perpendicular profile, TS02, along a section of more than 100 km in length crossing the Rivera transform zone, and the plate boundary between Cocos and Rivera Plates. Northwards, offshore Pto. Vallarta, the MCS data reveals high amplitude reflections at around 7-8.5 s TWTT, roughly 2.5-3.5 s TWTT below the seafloor, that conspicuously define bending plane (TS06b). These strong reflections interpreted as the Moho discontinuity define the starting bending of subduction of Rivera Plate. Moreover, big acoustic energy source array (8000 in3) were recorded by 16 OBS’s at 32 locations, in Jalisco and Nayarit offshore regions, as well as on a terrestrial network (100 portable seismic stations) in 240 locations across 5 seismic profiles of 200-300 km in length combined with the Seismological Network of the State of Jalisco (SisVOc). This configuration allows sampling the crustal structure down to the Moho, besides conspicuous crustal variations are obtained from WA data showing slow crustal velocities underneath Maria Magdalena Rise (MMR), and a clear crustal thickening at the NE tip of Marias Islands. All these new data will illuminate the complex interactions between Rivera and North American Plates, giving a new insight of the Geodynamics at the Northern edge of these Plates