Investigating the Geometry of an Unnamed Fault System South of Socorro, New Mexico, Using an Integrated Geophysical and Remote Sensing Approach

Active faults within continental rift zones, such as the Rio Grande rift (RGR), pose hazards to society. Evaluations of earthquake hazard along active faults require models of subsurface geometry and estimates of fault activity rates. South of the city of Socorro, New Mexico, a series of normal faults – including the Socorro Canyon Fault Zone (SCFZ) – mark the eastern boundary of the Chupadera Mountains in the RGR. Despite the seismic hazard posed by these fault systems to surrounding communities, their subsurface geometry is not well-constrained. Here we use a variety of interdisciplinary geophysical techniques, including ground penetrating radar (GPR) and seismic reflection surveying, to image the subsurface architecture of this complex fault system. We also use recently released high-resolution lidar imagery to relate scarp morphology in unconsolidated alluvial fans to relative fan age in order to establish Quaternary fault activity. Our geophysical imaging surveys show offset of reflectors consistent with normal faulting. Relative fan age estimates and analysis of scarp morphology indicate that this system has remained active throughout the Quaternary. This recent activity warrants further investigation into the seismic hazard posed by this system, including possible linkages between this and surrounding structures in large earthquakes. Future work includes extending the study area along-strike and cosmogenic nuclide dating of alluvial fans to further constrain the slip history of the faults.