Seismic Imaging of the Rivera-Cocos-North American Plate Interaction Zone

Abstract:

The complexity of the interactions between tectonic plates is especially relevant in the western margin of Mexico, where the convergence between Rivera and Cocos plates with Jalisco Block and North American plate is vaguely known. In this work, we modeled two seismic profiles of 170 km length, the wide-angle seismic (WAS) transect RTS01, acquired by 16 Ocean Bottom Seismometers (OBS), and the multichannel seismic (MCS) profile TS02, coincident with RTS01 and both recorded during the active stage of the TsuJal experiment in February 2014. During this project, the RRS James Cook oceanographic vessel was responsible for anchoring the OBS, deploying the 5.85 km long streamer, as well as generating the seismic source of 8000 in3 and 5800 in3 to obtain the WAS and MCS seismic profiles, respectively.

The new data acquired in these profiles perpendicular to the Mesoamerican Trench provide a dense sampling of the plates studied to characterize and establish further tectonic implications, and new images on cortical deformation through the subduction zone where significant earthquakes and tsunamis occurred in the past. The results obtained after the data processing and interpretation phases are consistent with an oceanic crust 6-8 km thick, on a mantle where the P wave velocities reach values of 7.9-8.0 km/s in this region. Furthermore, our models describe the dimensions of the accretionary prism, and new features of the contact zone where the Rivera plate is dipping with an angle between 12°-15° under Jalisco Block, improving the knowledge about the transition between the oceanic and continental crust in the southern region of the Rivera plate.