Collaborative Research: Mapping the Rivera Subduction Zone

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The investigators plan to deploy fifty broadband seismic instruments throughout the Jalisco and Colima provinces in Mexico. This region of Mexico is being underthrust by the Rivera microplate and has witnessed the largest earthquake in Mexican history. The subduction of the Rivera plate has also resulted in the overriding plate, the Jalisco block, separating from the rest of Mexico along two perpendicular grabens. The Jalisco block is also volcanically active with the Colima volcano unusually close to the trench. This region is a type example of the processes that can occur when a ridge meets a subduction zone. The tectonics of the region has been postulated to be due to the interaction of the Rivera plate and the overriding Jalisco block but little geophysical data exist to truly understand the subsurface interactions. In this project researchers will image the geometry of the Rivera plate at depth including a search for tears with the adjacent Cocos plate or evidence of breaking up of the Rivera plate at depth, both of which have been postulated. In this work tomographic imaging tools as well as receiver function analysis will be employed. Careful mapping of the slab surface as well as the locations and mechanisms of earthquakes in the region will provide constraints on the region of coupling between the Jalisco and Rivera plates. This will provide useful information for the ongoing GPS projects funded by NSF in this region that will ultimately help with hazard analysis. The investigators will also attempt to image the mantle wedge to better understand the volcanism in the region. Using shear wave splitting we hope to understand mantle flow beneath the Jalisco block. This study should have broader impact in understanding the evolution of plate boundaries when ridges interact with subduction zones. This has occurred in the geologically recent past off the coast of California and northern Mexico. This research includes a substantial international collaboration with Mexican colleagues from several institutions.This project is co-sponsored by the Americas Program in the Office Of International Science And Engineering.--