High-Resolution Topographic Analysis of the Late Quaternary Deformation of Crowley's Ridge, New Madrid Seismic Zone

Date: 4/25/2019

Time: 04:00 PM

Room: Pike

The New Madrid seismic zone in the central Mississippi Valley was the source of multiple major (M ~7.0-7.5) earthquakes in the past 2 ka, yet the surface expression of recent deformation remains ambiguous. Crowley’s Ridge trends north-south for 300 km through the Mississippi River embayment and has been interpreted as either a fault-bounded uplift block or a non-tectonic erosional remnant. New and previously published seismic reflection data show primarily steeply-dipping apparent normal and reverse faults that bound the central and southern parts of the ridge, but the timing of most recent faulting and the lateral extent of these faults along the ridge remains unknown. Because of the uncertain origin and age of potential faults bounding Crowley’s Ridge, the faults are currently not included in the CEUS-Seismic Source Characterization or the USGS National Seismic Hazard Model. To assess the proposed Pleistocene-to-recent tectonic activity of Crowley’s Ridge, we use landscape-scale geomorphic analyses, such as patterns of relief, slope, hypsometry, and drainage basins, on a 10-m DEM. North-to-south variations in geomorphic indices suggest Pleistocene-to-recent tectonic uplift of the southern half of the ridge. In addition, using a <1-m lidar-derived DEM, we map scarps on late Pleistocene geomorphic surfaces. The scarps are primarily located along the southern segment of the ridge, trend parallel to the margin of the ridge discontinuously for 100 m to 1 km, and vertically offset <55 ka surfaces by 0.4 to 6 m. These landscape-scale deformation patterns and apparent fault and fold scarps, along with a synthesis of the seismic reflection data, provide evidence of low-rate (<0.2 mm/yr) late Quaternary tectonic activity along the southern segment of Crowley’s Ridge. The interpretations are generally consistent with recent tectonic models suggesting the southern part of the ridge is an active compressional step-over in a right-lateral fault system within the Reelfoot Rift.

Presenting Author: Jessica A. T. Jobe

Authors