Quaternary deformation and fault structure in the Northern Mississippi Embayment as imaged by near‐surface seismic reflection data

Abstract

Seismicity in the New Madrid seismic zone (NMSZ) in the central United States constrains the location of present deformation at depth along four main distinct arms, while the surface expression of the ongoing deformation is still unclear. To better constrain the surface deformation in the NMSZ, we integrate existing seismic reflection data with a new~300 km-long high-resolution seismic reflection profile acquired along the Mississippi River from Cape Girardeau, MO, to Caruthersville, MO. Based on the data, we interpret the Reelfoot Thrust and the New Markham Fault as upward splays of a blind master fault defined by the seismicity and extending at depth farther north. To the south, two faults, the Axial Fault and the Cottonwood Grove Fault, are imaged above the southern arm of the NMSZ. Both fault display deformation of the Paleozoic through the Tertiary sediments, and a relief of~20-25 m at the base of the Quaternary alluvium, which we interpret as the result of strike-slip motion along a complex fault plane geometry. We propose two alternative interpretations for the relationship between the shallow faults and the seismicity in this area: (1) the faults merge at depth and are presently both active and (2) the faults are distinct at depth and were active during the Quaternary and only the Axial Fault is presently deforming. Geological structures mapped at the surface as part of this study show that Quaternary deformation is accommodated along a fault network that is more complex than the simple four-arm system illuminated by the seismicity, a behavior predicted by analog and computer models.

Lake County, Tennessee, in the Heart of the New Madrid Seismic Zone

“…Axial fault (AF) is shown to the west of Ridgely ridge. New Markham fault (NMF) interpreted by Guo et al (2014) (red barbed dashed-line) and original interpretation by Odum et al (1994Odum et al ( , 1998 and Van Arsdale et al (1998) (blue dashed-line). Small inset map shows NMSZ (Johnston, 1996) [modified from Purser and Van Arsdale (1998)].…”

“…FIGURE 3 | Lake County, Tennessee with locations of Cross-Sections A-A', B-B', and C-C'. Red (NMF) and blue (NMF) dashed lines represent Guo et al (2014) and Odum et al (1998) interpreted locations of the NMF, respectively. Brown dashed lines represent previously interpreted faults.…”

“…Several faults have been mapped in and adjacent to Lake County (Figures 1-3). The AF is a near-vertical NE-striking, dextral, strike-slip fault that is the southwestern arm of the NMSZ (Johnston and Schweig, 1996;Magnani and McIntosh, 2009;Guo et al, 2014;Magnani et al, 2017). The AF is believed to be responsible for the December 16th, 1811 ∼M 7.5 earthquake (Cramer and Boyd, 2014) and bisects the Reelfoot reverse fault into two segments; the Reelfoot North fault and the RSF (Figure 1).…”

Long-lived deformation in the southern Mississippi Embayment revealed by high-resolution seismic reflection and sub-bottom profiler data

“…[] and Guo et al . []. This project employed marine seismic acquisition techniques and sub‐bottom profiling to identify Quaternary and older deformation within the sedimentary units of the Mississippi Embayment.…”

“…This project employed marine seismic acquisition techniques and sub‐bottom profiling to identify Quaternary and older deformation within the sedimentary units of the Mississippi Embayment. Our purpose was to identify, constrain, and characterize potential seismogenic faults, and to understand the long‐term deformation pattern of intraplate earthquakes in the Central U.S. [ Magnani and McIntosh , ; Hao et al ., ; Guo et al ., ]. The Mississippi River Project acquired high‐resolution multichannel seismic reflection data with unprecedented quality for ~950 km from Cape Girardeau, Missouri, to 30 km south of the Arkansas‐Louisiana border.…”