SH-wave Seismic-Reflection Efficiency Technique for Investigating the Wolf Island Fault, New Madrid Seismic Zone, USA

The Reelfoot Fault within the New Madrid seismic zone has displacement at seismogenic depth to which the surface expression has unequal displacement. Previous work identified northeast-oriented transpressional fault strands northeast of a bend in the scarp as evidence for a through-going shear-zone, acting as potential accommodation for the observed strain imbalance. This investigation projected the trend of these faults to their intersection with an industry seismic survey at Wolf Island, Missouri, which exhibits a similarly structured faulted zone. We suggest this structure is the continuation of the through-going shear zone representing a previously unknown 22-km-long Quaternary-active fault that can affect the seismic hazard for the northern Mississippi embayment. SH-wave and P-wave reflection surveys were conducted across the target structure to provide near-surface imaging, including the Quaternary-Tertiary boundary. The SH-wave data show high-angle faults with deformation with up to ~10 m of relief in the lower Quaternary-Tertiary sediment, and ~1 m of relief extending to 5 meters depth. For this investigation, we built a SH-wave landstreamer to compare against direct-plant receivers. Our observations show a reduced spectral peak of ~10 Hz for the sled-mounted receivers. In this environment, it was determined to be an acceptable loss, with drastically improved acquisition efficiency.