Microseismicity in the Ste. Genevieve, Wabash Valley and Rough Creek seismic zones using EarthScope FlexArray data: Implications for earthquake hazards: Collaborative Proposal with Indiana University, Purdue University, and University of Kentucky

This proposal requests USGS funds for a collaborative project to analyze observations of microearthquakes recorded by a dense, broadband seismic array extending across three major intraplate seismic zones in the central U.S. The OIINK (“Ozarks-Illinois-INdiana-Kentucky”) seismic array is an EarthScope FlexArray experiment embedded within the national USArray network. Although the array was originally designed for analysis of deep crustal and mantle structure, the 140-station network provides a unique resource for high-resolution analysis of small-magnitude earthquakes in the Ste. Genevieve, Wabash Valley, and Rough Creek seismic zones. We propose to build on a pilot experiment focusing on the Ozark-Illinois Basin transition zone and extend those analyses to provide detailed information on three years of seismic recording in the OIINK study area. We will use high-precision earthquake locations and focal mechanism determinations to identify and characterize low-level seismicity associated with reactivated Precambrian and Paleozoic structures in the region, and to correlate seismicity with newly imaged seismic velocity anomalies identified by analysis of OIINK data. The analysis will include development of new, semi-automated techniques to identify and discriminate naturally occurring earthquakes from the thousands of mine and quarry blasts that occur in the region each year. We also will use our analysis to identify possible sites of triggered (induced) seismicity associated with oil and gas exploration in the Illinois Basin and Rough Creek Graben. The project will provide valuable constraints to improve understanding of regional geodynamics, including interactions between two of the midcontinent’s major, seismically-active source regions, and thus address crucial issues for assessing earthquake hazards in the region.