THE CRINER FAULT IN SOUTHERN OKLAHOMA : ASSESSING SEISMIC HAZARD IN THE CENTRAL AND SOUTHEAST UNITED STATES

Resolving the issue of potential Quaternary activity on the Criner fault in southern Oklahoma has significant implications for seismic hazard assessment in the central and southeastern United States. The fault strikes NW-SE and is coincident with a SW-facing scarp in Oklahoma, similar to the expression of the Meers fault ~120 km along strike to the northwest. Given the evidence for Quaternary activity along the Meers fault, workers have speculated that the Criner may also have been active in the Quaternary. However, previous workers have also suggested the escarpment is a fault-line scarp and has been modified by landsliding. In Love and Carter counties, Oklahoma, the escarpment is ~10-km-long and 0.5 to 2-m-high. The bedrock ledge is neither smooth nor striated and transitions into a more rubbly, rounded, and vegetated slope NE of the fault's trace. Southwest of the faults trace, there is little to no colluvial wedge, but instead the flat plain abruptly transitions into the bedrock scarp and fractured outcrops of Ordovician limestone. In one location, a 7 to 10-m-wide soil exposure essentially extends obliquely across the most likely projection of the fault. This soil is moderately well-developed and includes secondary clay accumulation, a >40-cm-thick Bt horizon, a 0.5-m-thick A horizon, Stage II carbonate accumulation, and reddening. Since no evidence of faulting was found in this outcrop which should reveal the likely projection of the fault, we interpret the faulting to be older than the development of this soil unit. Farther southeast, a landslide was mapped adjacent to an exposure previously interpreted as indicating Pleistocene faulting along Hickory Creek. This landslide and exposures within it yield no evidence for tectonic slip on any of the post-Pennsylvanian units. At the NW extent of the scarp, no geomorphic expression of faulting is found within an uninterrupted alluvial plain. No obvious faulting of Quaternary fluvial units was found along the trace of the Criner fault, and the escarpment was limited to locations where the Criner fault juxtaposes units of different erosion resistance. This evidence is most compatible with the interpretation that the escarpment is a fault-line scarp resulting from the exposure of the Pennsylvanian Criner fault.