Coseismic Sackungen in the New Madrid Seismic Zone, USA

Abstract

High-resolution lidar reveals newly recognized evidence of strong shaking in the New Madrid seismic zone in the central United States. We mapped concentrations of sackungen (ridgetop spreading features) on bluffs along the eastern Mississippi River valley in northwestern Tennessee that likely form or are reactivated during large earthquakes. These sackungen are concentrated on the hanging wall of the Reelfoot reverse fault and show a preferential orientation indicating ground failure normal to fault strike. These observations suggest that the sackungen record one or more earthquakes on the southern Reelfoot fault since the deposition of the ~30- to 11-ka Peoria Loess and potentially constrain the minimum intensity of near-fault ground motion. This study demonstrates that sackungen can be used to infer fault source and mechanism and, in combination with field-based techniques, improve paleoseismic records and seismic hazard models.