Quaternary faulting in the southern Mississippi embayment and implications for tectonics and seismicity in an intraplate setting

Tectonic Framework of the Southwestern Margin of the Illinois Basin and Its Influence on Neotectonism and Seismicity

“…One of these trends is beneath the Ohio River Valley ( Figure 13) and possibly corresponds to a buried fault identified by Davis et al (1973) in Paleozoic strata. Several Quaternary faults have been identified in the Smithland, Kentucky area (Harrison and Nelson, 1993), in southernmost Illinois (Nelson et al, 1997;Nelson et al, 1999), and in northeastern Arkansas (Van Arsdale et al, 1995;Cox et al, 2000). All of these structures lie in the southern domain, southeast of the CGL.…”

Paleoseismic Sand Blows in North Louisiana and South Arkansas

“…Paleochannels and alluvial terraces show that throughout late Quaternary these rivers have been migrating westward, against the eastward dip of strata into the Mississippi embayment (Schumm et al 1982;Burnett and Schumm 1983;Cox 1994), and Pleistocene and Holocene alluvium is faulted and warped along these river alignments (Cox et al 2000;Cox, Harris et al 2004). The region is characterized by low historical seismicity, but the region is outside the low-magnitude detection range of the seismic networks operating in the central and eastern United States (Mitch Withers, personal communication, 2010), and the level of microseismicity is unknown.…”

Hammer-impact SH-wave seismic reflection methods in neotectonic investigations: General observations and case histories from the Mississippi Embayment, U.S.A.

“…In the Mississippi Embayment, SH-wave methods have been tested at numerous sites, mostly in support of earthquake hazard investigations (Cox et al, 2006(Cox et al, , 2001(Cox et al, , 2000Harris and Sorrells, 2006;Baldwin et al, 2005Baldwin et al, , 2002Woolery et al, 1999Woolery et al, , 1996Woolery et al, , 1993Harris et al, 1998). Figure 2 shows representative field data (from Memphis, Tennessee and Paducah, Kentucky) exhibiting the range of depths (<10 m to >100 m) imaged by hammer-impact, SH-wave reflection methods in the Mississippi Embayment.…”

“…1 for location). As mapped at the surface in a paleoseismologic trench (Cox et al, 2000), the faults displace Tertiary clay and gravel and Holocene silt. The seismic profile shows strong reflection energy to depths in excess of 150 m. The most coherent reflection is from a depth of 110 m and, based on correlation with local well data, is interpreted to represent the top of the Eocene Cockfield (sand) Formation.…”

“…Although P-wave (compressional wave) reflection methods have been used for 30 years for imaging faults in the Paleozoic through Tertiary deposits of the Mississippi Embayment (e.g., Stephenson et al, 1999;Williams et al, 1995;Schweig et al, 1992;Sexton and Jones, 1986;Zoback, 1979), only in the last two decades has detailed seismic investigation of deformed Quaternary sediments, primarily using S-wave (shear wave) methods, been undertaken (e.g., Cox et al, 2006Cox et al, , 2001Cox et al, , 2000Harris and Sorrells, 2006;Baldwin et al, 2005Baldwin et al, , 2002Woolery et al, 1999Woolery et al, , 1996Woolery et al, , 1993Harris et al, 1998). One of the principal justifications for using S-waves is the potential for increased seismic resolution (compared with conventional Pwave methods) in the water-saturated, shallow sediments of the Mississippi Embayment-an important consideration in light of the modest surface deformation in the region.…”