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

Rafael Bartolome,Jose Luis Alonso,Carlos A Mortera-Gutiérrez,Francisco Núñez-Cornú,Diana Nuñez,David Martí,Juanjo Dañobeitia,Estefanía Górriz,William L Bandy,Diego Cordoba,Alejandra L Cameselle,Arturo Castellón

doi:10.1007/s00024-016-1331-y

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.

Highlights

Subduction is the geodynamic process by which one tectonic plate converges with and slides beneath another tectonic plate, sinking into the mantle; its motion being driven by the higher density of the descending oceanic slab with respect to the surrounding mantle asthenosphere
The interpretation of the geodynamic and tectonic features imaged by seismic profile TS06b is placed within the general framework of the subduction of the oceanic Rivera plate beneath the North American plate (NA) plate, crossing the lower slope of the margin
Two large areas with different tecto-sedimentary features can be distinguished in the profile: the western area, formed by the subducting oceanic Rivera plate and sedimentary marine deposits above it; and the eastern area, formed by the accretionary prism and the associated sedimentary basins belonging to the continental NA plate which overly the

Summary

Introduction

Subduction is the geodynamic process by which one tectonic plate converges with and slides beneath another tectonic plate, sinking into the mantle; its motion being driven by the higher density (colder) of the descending oceanic slab with respect to the surrounding mantle asthenosphere. Recent research based mainly on the 2011 Tohoku event has suggested that the generation of huge tsunamis may require the release of gravitational energy as well as elastic energy (GEORGE et al 2011). This gravitational energy comprises primarily crustal wedge uplift. When a megathrust earthquake occurs, gravitational energy is discharged by the formation of giant landslides or the rigid motion of a crustal block sliding though a normal fault or splay faults that may

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