Collaborative Research: Mapping the Rivera Subduction Zone

研究人员计划在墨西哥哈利斯科州和科利马省部署50台宽带地震仪器。墨西哥的这个地区正处于里维拉微板块的逆冲之下，并见证了墨西哥历史上最大的地震。里维拉板块的俯冲也导致了上覆板块哈利斯科板块沿着两条垂直的地堑与墨西哥其他地区分离。哈利斯科区块的火山活动也很活跃，科利马火山异常靠近海沟。这个地区是一个典型的例子，当脊与俯冲带相遇时可能发生的过程。该地区的构造被认为是由里维拉板块和哈利斯科地块的相互作用造成的，但很少有地球物理数据能够真正理解地下的相互作用。在这个项目中，研究人员将对里维拉板块的深度几何形状进行成像，包括寻找与邻近的科科斯板块的撕裂，或里维拉板块在深度上分裂的证据，这两种情况都是假设的。在这项工作中，层析成像工具以及接收函数分析将被使用。仔细绘制该地区的板块表面以及地震的位置和机制，将对哈利斯科和里维拉板块之间的耦合区域提供约束。这将为美国国家科学基金会在该地区资助的正在进行的GPS项目提供有用的信息，最终将有助于危害分析。研究人员还将尝试对地幔楔进行成像，以更好地了解该地区的火山活动。利用横波分裂，我们希望了解哈利斯科地块下的地幔流动。这项研究将对理解当脊与俯冲带相互作用时板块边界的演化具有更广泛的影响。这种情况在最近的加利福尼亚海岸和墨西哥北部发生过。这项研究包括与来自几个机构的墨西哥同事进行大量国际合作。本项目由国际科学与工程办公室美洲项目共同主办

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.--