146-1 Airborne Electromagnetic Inversion Results Validate Analog Model Predictions of Strike-Slip Fault Reactivation and Potential for Hydrogeologic Compartmentalization

Abstract:

The New Madrid seismic zone overlies the Reelfoot Rift (RR), an intracontinental extensional structure reactivated as a strike-slip system during Phanerozoic. Complex fault interactions in this region including the 1811–1812 New Madrid earthquake sequence and modern seismicity reflect incomplete understanding of fault geometry and strain partitioning across the region. Traditional borehole-based subsurface mapping and seismic reflection reveal broad structural trends, but subsurface fault-zone architecture and precise fault orientations remain poorly constrained. Many scaled analog models predict development of Riedel shear arrays and secondary structures during strike-slip reactivation; however, systematic validation of these predictions using high-resolution geophysical data has not been applied yet. We apply airborne electromagnetics (AEM) to image subsurface fault geometry and electrical conductivity anomalies in Eocene-Quaternary sediments deformed along the southeastern margin of the New Madrid seismic zone. We compare AEM-derived fault orientations, kinematic indicators, and structural geometries with previous analog model predictions for progressive strike-slip reactivation. Specifically, we test whether the RR system exhibits the characteristics of Riedel shear components predicted in analog models. AEM data reveal (1) the continuity of the previously identified faults while also delineating several previously unidentified faults, (2) the geometry and orientation of newly identified and previously mapped faults, providing the basis for constructing a new regional cross section that more accurately represents the structural framework than earlier interpretations, (3) characteristics of en echelon fault spacing and segmentation patterns matching analog model predictions, and (4) distributed shear zones with widths correlating to model-predicted stress partition between primary and secondary faults. This study validates analog model predictions for strike-slip fault evolution within the RR system and establishes a quantitative framework for interpreting fault-zone complexity in this seismically active region. These findings also clarify the distribution and structural style of fault zones that may provide lateral compartmentalization of the Memphis aquifer, a regionally important and vulnerable water resource.

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