REINTERPRETATION OF THE MEEMAN-SHELBY FAULT’S STRUCTURE

The Meeman-Shelby Fault (MSF), located 5 km west of Memphis, Tennessee, is an active fault argued to be capable of generating a moment magnitude (M) 6.9 earthquake. Previously the MSF has been described as a NNW to NE striking, reverse fault. However, we suggest that there is an incomplete understanding of the MSF’s structure. The fault has not been identified in the basement and there is disagreement in prior work on the faults strike direction. As well, the MSF was extended to the south by the interpolation of sparse seismic reflection profiles. To improve understanding of the MSF’s structure, we used the horizontal gradient maximum (HGM) on aeromagnetic data to identify structures in the magnetic basement associated with the MSF. Mapping magnetic HGM with constraints of previous research, we interpret the MSF to be five independent faults, as opposed to a continuous structure. The northernmost fault, MSF-I, is associated with eastern Reelfoot Rift margin faults and strikes 040^°. To the southwest, MSF-II strikes 279^°, and MSF-III strikes 007^°. MSF-II and III are interpreted to have minimal offset in the basement based on the small magnitude of the HGM, suggesting they may both be strike-slip faults. MSF-IV is the longest of the interpreted faults and consists of three segments, which vary in strike direction from 327^° to 005^°. MSF-V is located furthest to the southwest and is interpreted to have three segments varying in strike direction from 054^° - 123^°. Both MSF-IV and V are associated with large HGM values and may be the result of large offset on basement normal faults. We interpreted faults MSF-II through MSF-V to lie outside of the Reelfoot Rift. Our interpretations indicate that paleoseismic data used to describe reactivation history of the MSF may only apply to a fault segment, not the whole of the fault system. Based on the relationship of subsurface rupture length to M potential, the largest earthquake our interpreted faults may generate is a M 6.5, lowering the M potential of the MSF. We recognize that resolution of the aeromagnetic data may not allow us to resolve the fine scale structure of the MSF. However, we argue that it provides a significant improvement in the structural framework of the MSF and provides target areas for future research.