The plate tectonic theory provides a framework to interpret earthquakes located along plate boundaries, but it fails to explain the earthquakes that occur inside the tectonic plates, such as those occurring along the New Madrid seismic zone (NMSZ), located in the central U.S. (Figure 1). Here the present, historical, and prehistorical seismicity [Johnston and Schweig, 1996; Tuttle et al., 2002; Chen et al., 2006] appears to conflict with the apparent low rates of deformation at the surface (less than ~1.4 mm/yr) [Newman et al., 1999; Calais et al. 2006; Calais and Stein, 2009; Vidale et al., 2011; Frankel et al., 2012]. A hypothesis proposed to resolve this conflict is that deformation may be focused in different areas at different times and that the present seismicity might not reflect the long-term behavior of the seismogenic faults in the area [Pratt, 1994; McBride et al., 2002; Crone et al., 2003; Stein and Newman, 2004; Stein, 2007; Calais and Stein, 2009; Stein et al., 2009; Liu et al., 2011]. One important implication of this hypothesis is that seismogenic faults might exist outside the NMSZ, buried beneath the sediments of the Mississippi Embayment (Figure 1), potentially posing a seismic hazard to the region. Evidence corroborating this hypothesis is also provided by earthquake-induced liquefaction features observed at several locations in the Mississippi Embayment (e.g., in the Wolf River floodplain in Memphis, Tennessee [Broughton et al., 2001], near Marianna, Arkansas [Tuttle et al., 2006], and near the Arkansas-Louisiana border [Cox et al., 2007]). The age of these venting episodes shows no correlation with the age of large earthquakes in the NMSZ (clustered at A.D. 900, A.D. 1450, and in 1811–1812 [Tuttle et al., 2002]) and together with their location (in some cases identified at distances up to ~350 km from the NMSZ) indicate the existence of additional seismic sources outside the NMSZ active during the Quaternary. As increasing evidence for multiple faults active at different times in the central U.S. emerges [Howe and Thompson, 1984; Howe, 1985; Crone et al., 1995; Luzietti et al., 1995; Williams et al., 1995; Stephenson et al., 1995; Schweig and Van Arsdale, 1996; Odum et al., 1998; Williams et al., 2001; Parrish and Van Arsdale, 2004; Baldwin et al., 2005; Bexfield et al., 2005; Velasco et al., 2005; Bexfield et al., 2006; Harris and Sorrells, 2006; Csontos et al., 2008; Harris, 2009; Odum et al., 2010], it becomes crucial to understand the location, timing, and character of these faults, whether a pattern exists among the activity of the fault systems, and the tectonic mechanism(s) that control the localization of deformation along them.
Figure 1. Regional map of the main tectonic features in the Mississippi Embayment. The location of the Western Reelfoot Rift Margin and the Eastern Reelfoot Rift Margin (WRRM and ERRM, respectively) is based on potential field data interpretations of Hildenbrand and Hendricks . Seismically active faults in the embayment include the New Madrid North Fault (NMNF), the New Madrid West Fault (NMWF), the Reelfoot Thrust, divided into the North Reelfoot Fault (NRF) and the South Reelfoot Fault (SRF), and the Axial Fault (AF) [Johnston and Schweig, 1996; Csontos and Van Arsdale, 2008; Tavakoli et al., 2010; Pratt, 2012]. Additional relevant faults imaged by high-resolution surveys include the Bootheel Fault (BHF), the Crittenden County Fault Zone (CCFZ), and the Meeman-Shelby Fault (MSF) [Schweig and Marple, 1991; Crone et al., 1995; Guccione et al., 2005; Luzietti et al., 1995; Williams et al., 1995; Williams et al., 2001; Odum et al., 2010]. Dots indicate seismicity (CERI New Madrid Earthquake Catalog 1996–2012, M0.2–M4.7).
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 In order to test the aforementioned hypothesis and to identify the faults buried beneath the unconsolidated sediments of the Mississippi Embayment, a series of high-resolution seismic reflection surveys were carried out along and near the Mississippi River between 2008 and 2011 as part of the Mississippi River Project [Magnani and McIntosh, 2009]. Here we present the results of five profiles that imaged a ~45 km long fault both on land and along the river, interpreted as the Meeman-Shelby Fault (MSF), near Memphis, Tennessee. In addition to seismic multichannel reflection data, coincident sub-bottom profiler (CHIRP) data were acquired during the marine survey along the Mississippi River to help constrain the detailed shallow structure and the more recent deformation history of the imaged MSF.