Multichannel Seismic Imaging of the Rivera Plate Subduction at the Seismogenic Jalisco Block Area (Western Mexican Margin)

Abstract

Abstract-During the TSUJAL marine geophysical survey, conducted in February and March 2014, Spanish, Mexican and British scientists and technicians explored the western margin of Mexico, considered one of the most active seismic zones in America. This work aims to characterize the internal structure of the subduction zone of the Rivera plate beneath the North American plate in the offshore part of the Jalisco Block, to link the geodynamic and the recent tectonic deformation occurring there with the possible generation of tsunamis and earthquakes. For this purpose, it has been carried out acquisition, processing and geological interpretation of a multichannel seismic reflection profile running perpendicular to the margin. Crustal images show an oceanic domain, dominated by subduction-accretion along the lower slope of the margin with a subparallel sediment thickness of up to 1.6 s two-way travel time (approx. 2 km) in the Middle American Trench. Further, from these data the region appears to be prone to giant earthquake production. The top of the oceanic crust (intraplate reflector) is very well imaged. It is almost continuous along the profile with a gentle dip (\10°); however, it is disrupted by normal faulting resulting from the bending of the plate during subduction. The continental crust presents a well-developed accretionary prism consisting of highly deformed sediments with prominent slumping towards the trench that may be the result of past tsunamis. Also, a bottom simulating reflector (BSR) is identified in the first half a second (twtt) of the section. High amplitude reflections at around 7-8 s twtt clearly image a discontinuous Moho, defining a very gentle dipping subduction plane.

Crustal Architecture at the Collision Zone Between Rivera and North American Plates at the Jalisco Block: Tsujal Project

“…Recent studies also evidence gas hydrates in the western (Minshull et al 2005;Bartolome et al 2011Bartolome et al , 2016Bandy and Mortera 2012) in the form of bottom simulating reflectors (BSR) on multichannel seismic reflection profile located on the continental slope area of the northern part of the Jalisco Subduction Zone, off Puerto Vallarta, between 20°and 20.5°N, and in the south off Manzanillo. Thus, there is evidence to suggest that the Pacific margin of Mexico may contain significant reserves of hydrocarbons in the form of gas hydrates.…”

Trench-parallel ridge subduction controls upper-plate structure and shallow megathrust seismogenesis along the Jalisco-Colima margin, Mexico

“…From north to south, the upper plate of this subduction system exhibits two different tectonic regimes. From the northernmost region of the Middle America Trench (MAT) to 19.2°N latitude, the continental margin is controlled by a subduction-accretion regime as evidenced by a well-developed accretionary prism observed from seismic images 9,10 . South of 19.2°N, the margin is highly eroded and non-accretionary, and it is characterised by several slope failure scars visible from bathymetry 11 (Fig.…”