NE-SW fault system in the eastern sector of the Trans-Mexican Volcanic Belt: Origin, deformation, and reactivation

A NE-SW fault system described in the eastern sector of the Trans-Mexican Volcanic Belt (TMVB) has been active since the Pliocene and continued up to the Holocene with dip-slip kinematics. In a broad view, these NE-SW faults can be correlated to the Tenochtitlan fault system that extends from the southwest coast of Mexico to central Mexico, into the TMVB. The length of the faults, the damage zone width, and more than one slickensides on the fault planes suggests a complex deformation history. In this study, we investigate the geometry and kinematics of the NE-SW faults in the Miocene-Pleistocene rocks in the eastern sector of the TMVB to determine the kinematics of these faults during the Late Miocene to Holocene, for which it is unknown. Our results suggest that the Miocene rocks record two deformation events, one of which is related to crustal shortening that produced a strike-slip activity in the NE-SW faults during the Late Miocene. The second one is associated with crustal extension and the activity of the NE-SW faults with dip-slip kinematics. This extensional event was active during the Pliocene-Holocene. The reactivation analysis and our field observations suggest that the NE-SW normal faults are related to the reactivation of previous NE-SW strike-slip faults. The change in the kinematics of the NE-SW faults explains the complex geometry of the damage zones of the kilometric NE-SW faults and the highly fractured Miocene rocks.

Based on the fault system orientation, it is clear that these faults are incompatible with the field stress recorded in the eastern sector of the TMVB. This fact suggests that the NE-SW fault system is probably related to reactivated basement structures within a three-dimensional deformation with a complex deformation history. The activity type of the NE-SW faults is probably related to the dynamics of the subduction process in the southwest of Mexico, associated with the change in the dip (decrease) and the convergence velocity of the Cocos plate.