35 Recent advances in our understanding of the New Madrid seismic zone

Thorough understanding of the New Madrid seismic zone will require integration of observations relating to surface features, the crust and the upper mantle. All contributions are welcomed.

Wednesday, 11 March 2026
8:30 AM - 12:00 PM
RCC, 104

Kinematics of Late Quaternary Faulting Along the Eastern Reelfoot Rift Margin Revealed by Electric Resistivity Tomography (ERT)

Paper number: 35-2
Program: Technical Sessions
Time: 9:00 AM – 9:15 AM

Authors

Abstract

Most instrumentally recorded earthquakes in the eastern United States are in the New Madrid seismic zone (NMSZ) in the lower Mississippi River valley.  The NMSZ follows a NE-trending, right-lateral strike-slip fault system with a NW-trending left stepover thrust segment.  The eastern edge of the NMSZ is the NE-trending eastern Reelfoot rift margin (ERRM).  The historic rate of seismicity on the ERRM is relatively low, but paleoseismic studies reveal strong earthquakes occurred on the ERRM during Holocene and Late Pleistocene.  This study reports the first use of electrical resistivity tomography (ERT) to study neotectonic faulting along the ERRM, as well as the NMSZ in general.  The ERRM has a NE segment and a SW segment that are divided by the intersection of the ERRM with the southeastern end of the Reelfoot thrust fault.  At the Warren Quarry site on the SW ERRM segment, ERT images a fault-propagation fold indicating a shallow south verging thrust that may be associated with a relatively minor left stepover on the ERRM.  Farther northeast on the SW ERRM at the Porter Gap paleoseismic trench site, ERT reveals ~35 to 40 m of Late Quaternary right-lateral offset and >4m throw, revising the trench-based slip estimates.  On the NE ERRM segment, where modern epicenters are largely absent, ERT-imaged fault propagation folds are consistent with Late Quaternary transpressional flower structure faulting.  These results suggest the ERRM is a principal element of the NMSZ fault system that may pose a potential seismic hazard in the long term.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411594

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