THE COMPLEX GEOMETRY OF COCOS UNDER MEXICO: OVERVIEW

The complex geometry of Cocos under Mexico was first described by Pardo and Suárez (1995), who delineated it based on hypocenter locations. Ten years later, large seismic experiments began shedding light on the detail of this complex geometry. The Mapping the Rivera Subduction zone (MARS) experiment, the Meso American Subduction Experiment (MASE), the Veracruz-Oaxaca (VEOX) experiment, and the Geometry of Cocos (GECO) experiment have produced diverse tomographies and receiver function profiles and have allowed waveform modeling to outline the separation between Rivera and Cocos beneath the Colima volcano, and to distinguish the geometry transitions from horizontal subduction under central Mexico, to a constant dip to the north and the south. Young slab tears, observed in tomographies and consistent with the observed anisotropy in the mantle, have been suggested to facilitate these slab geometry transitions. Also, the position of the active volcanism and its geochemical composition, as well as the distribution of the intermediate-depth seismicity, are an expression of the complex slab geometry. In this talk, I will present an overview of the geometry of Cocos under Mexico and will focus on the transition from horizontal to constant-dip subduction to the south.