GEOLOGIC AND PALEOSEISMIC CHARACTERIZATION OF THE NEW MADRID NORTH FAULT, FARRENBURG, MISSOURI

Based on existing geologic, geophysical, and historical data, the northeast-striking New Madrid North fault (NMNF) is inferred to have ruptured January 23, 1812, during an ~M7 earthquake. Despite the large size of the earthquake, little information is known on the location, style and timing of deformation of the NMNF. We evaluated two photo-lineaments near Farrenburg, MO, (North and South Farrenburg lineaments [NFL and SFL]) that intersect a Pleistocene topographic high and align with NE-trending contemporary microseismicity. The NFL and SFL are NE-trending, 3- to 4-km-long lineaments geomorphically expressed as apparent right-laterally deflected paleodrainages, scarplets, swales, linear troughs, and tonal contrasts. The lineaments also overlie a NE-trending, distinct change in thickness of Quaternary alluvium aligned with NE-trending microseismicity, aeromagnetic anomalies, and bedrock discontinuities. S-wave seismic reflection profiles across the lineaments image warped and faulted Quaternary deposits. Vibroseis data also image faults and folds in pre-Tertiary bedrock that align with the NFL and SFL, microseismicity, and NE-trending bedrock structures. Trench and borehole transects across the NFL encountered: (1) a ~N20°E trending zone of liquefaction-related dikes; (2) NNE-striking faults, (3) folding, and (4) soft sediment deformation, all of which overlie deformation imaged in seismic reflection and ground penetrating radar profiles. Microtextural analysis of sediment samples collected from the fault zones exhibit reduced grain size and preferentially oriented sand grains along fault contacts. Microstructural data, coupled with macro-fracture data from the trenches, indicate primarily dextral displacement and deformation of primary tectonic origin. Collectively, the geomorphic, geologic, geophysical, trench and microtextural data suggest that the NFL, and possibly SFL reflect late Holocene deformation related to the NMNF. From these data, we interpret deformation related to: (1) the 1811-1812 earthquake sequence, (2) one and possibly several late Holocene events, and (3) one to perhaps two late Pleistocene events.