Mesoscale structures in the Rough Creek Graben, U.S. Midcontinent craton: An integrated DEM analysis, structural modeling, and field-based approach

Abstract

The Rough Creek Graben (RCG) within the U.S. Midcontinent craton possesses some of the world's longest cave and karst landforms such as the Mammoth Cave. Despite the graben's position at the junction of two active seismic zones, the New Madrid Seismic Zone (NMSZ) and the Wabash Valley Seismic Zone (WVSZ), the RCG is seismically inactive. Here, we map mesoscale geologic structures within the RCG for understanding structural deformation and styles. We integrated DEM (Digital Elevation Model)-based structural analysis, field-based structural documentation, 3-d models, and GIS-based spatial analysis. Results of this integrated study reveal the presence of dominantly E-W-striking mesoscale structures with secondary NW-SE- and NE-SW-strikes. Many of these structures are documented in the field as high-angle normal faults with distinct fault cores, displacements, and damage zones. Most of the mapped structures are likely originated from extensional stresses associated with the development of the RCG. The presence of less frequent contractional structures (reverse and thrust faults, and folds) suggests subsequent strain localization within this graben. Although most of these structures are seismically inactive, understanding their deformation and kinematics is crucial for synthesizing any reactivation in response to a large magnitude earthquake originating from either the NMSZ or the WVSZ. The findings of this study not only advance our knowledge of the mesoscale structures in a midcontinent cratonic rift but also help evaluate potential earthquake hazards and risks. Moreover, positive correlations between these mesoscale structures and the karst systems suggest a relationship between these structures and the ultimate morphology of conduit systems that assisted in developing these karst landforms.