Seismic Imaging of the southern Rivera Plate and Jalisco Block Subduction Zone

Abstract

The importance of structural aspects and high seismic activity risk of the Jalisco Block makes the Pacific Coast of Mexico in one of the most attractive region for geophysical investigations. Furthermore, tectonic studies in this interesting geological region of the Rivera-North American contact zone, carried out during last two years by TSUJAL Project, are currently providing numerous geophysical results. In this study, we present the most relevant results in the southeastern part of the Rivera Plate-Jalisco Block area crossing the Mesoamerican Trench from to the east of Rivera Fracture Zone to La Huerta region (Jalisco state). Along this profile, we have combined wide-angle, multichannel seismic, multibeam bathymetry and seismicity data. The marine seismic sources used in this profile aboard RRS James Cook consisted of 12 guns divided in 4 subarrays of 3 guns each, with a total capacity of 5800 in3, shooting every 50 m and providing 1773 shots in a line of 89 km long. These sources were initially designed to recover multichannel seismic data, but 7 seismic portable stations were deployed perpendicular to the coast to register those sources providing a wide-angle offshore-onshore seismic transect of 130 km length with NE-SW orientation. The MCS data were also acquired aboard the RRS James Cook using a 5.85 km long digital streamer deployed at 10 m depth with 468 active channels. The WAS and MCS data processing and interpretation joined bathymetry afford new information about the geometry of southern Rivera Plate subducting under Jalisco Block with a dip angle of 14°, seismic images of the continental accretionary wedge and, also, the deep and shallow crustal structure along this profile up to maximum depth of 35 km