Tilting mechanisms in domino faults of the Sierra de San Miguelito, central Mexico

A system of normal faults with similar strike that bound rotated blocks in the Sierra de San Miguelito, central Mexico, was studied to determine the genesis of rotation and to estimate the extensional strain. We show that rigid-body rotation was not the main deformation mechanism of the domino faults in this region. We propose vertical or inclined shear accommodated by slip on minor faults as the mechanism for strain in the blocks. In order to test quantitatively the amount of strain, we calculated the extension assuming vertical shear obtaining ca. ev ~0.20. This value is in good agreement with extensions previously reported for the Mesa Central of México. The bed extension required in this model reaches ca. 33% of the total horizontal extension (i. e. ebed =0.34 ev). Assuming self-similar geometry for fault displacements, it is shown that bed strain required in shear models can be liberated by the small faults. If the strain is calculated using the rigid-body rotation model, the lengthening is underestimated by up to 9%. This case study shows that shear models could be applied in volcanic zones

Tilting mechanisms in domino faults of the Sierra de San Miguelito, central Mexico

A system of normal faults with similar strike that bound rotated blocks in the Sierra de San Miguelito, central Mexico, was studied to determine the genesis of rotation and to estimate the extensional strain. We show that rigid-body rotation was not the main deformation mechanism of the domino faults in this region. We propose vertical or inclined shear accommodated by slip on minor faults as the mechanism for strain in the blocks. In order to test quantitatively the amount of strain, we calculated the extension assuming vertical shear obtaining ca. ev ~0.20. This value is in good agreement with extensions previously reported for the Mesa Central of México. The bed extension required in this model reaches ca. 33% of the total horizontal extension (i. e. ebed =0.34 ev). Assuming self-similar geometry for fault displacements, it is shown that bed strain required in shear models can be liberated by the small faults. If the strain is calculated using the rigid-body rotation model, the lengthening is underestimated by up to 9%. This case study shows that shear models could be applied in volcanic zones