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Quaternary reelfoot fault deformation in the Obion River Valley, Tennessee, USA

August 6, 2021

Blind reverse faults are challenging to detect, and earthquake records can be elusive because deep fault slip does not break the surface along readily recognized scarps. The blind Reelfoot fault in the New Madrid seismic zone in the central United States has been the subject of extensive prior investigation; however, the extent of slip at the southern portion of the fault remains unconstrained. In this study, we use lidar to map terraces and lacustrine landforms in the Obion River valley and investigate apparent broad folding resulting from slip on the buried Reelfoot fault. We compare remote surface mapping results with three auger boreholes in the ∼24 ka Finley terrace and interpret apparent warping as due to tectonic folding and not stratigraphic thickening. We combine our results with historical records of coseismic lake formation that indicate surface deformation dammed the Obion River in the 1812 CE earthquake. Older terraces (deposited at least 35–55 ka) record progressive fold scarps ≥1, ≥2, and ≥8 m high indicating a long record of earthquakes predating the existing paleoseismic record. Broad, distributed folding above the Reelfoot fault into the Obion River valley is consistent with a deep active fault tip along the southern reaches of the fault. Our analyses indicate the entire length of the fault (≥70 km) is capable of rupture and is more consistent with longer rupture scenarios.

Publication Year 2021
Title Quaternary reelfoot fault deformation in the Obion River Valley, Tennessee, USA
DOI 10.1029/2019TC005990
Authors Jaime Delano, Richard W. Briggs, Jessica Ann Thompson Jobe, Ryan D. Gold, Simon E. Engelhart
Publication Type Article
Publication Subtype Journal Article
Series Title Tectonics
Index ID 70236812
Record Source USGS Publications Warehouse
USGS Organization Geologic Hazards Science Center