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Inferring Crustal Stress Distribution Within the Middleton Place/summerville Seismic Zone, South Carolina

The 1886 ~M7 Summerville earthquake in South Carolina remains enigmatic with no surface faulting evidence. Several studies (Mckinley, 1887; Chapman et al., 2016; Bilham and Hough, 2023) offer varying source fault interpretations in the Charleston-Summerville region, but the exact fault structure that ruptured during the 1886 mainshock remains unknown. Ongoing microseismicity near the Middleton Place/Summerville Seismic Zone (MPSSZ), possibly aftershocks of the 1886 mainshock, could shed light on the source fault and improve our understanding of seismic hazards in the area. Preliminary analysis of microseismicity in Summerville using a network of 19 temporary short-period stations from May 2021-May 2023 (Jaume et al., 2021) identified a south-striking, west-dipping zone in the southern seismicity cluster and a north-south striking near-vertical plane further north (Chen et al., 2023). From February to May 2023, we deployed two linear arrays with 22 stations in the study area. Currently, we reoccupied 14 of the 19 stations by 5-Hz Smartsolo nodes and added 6 new stations near the MPSSZ and in the under-monitored northern region towards Pinopolis. In this study, we plan to further develop our current results based on our analysis of 181 events detected from the first half of the temporary network continuous data presented at the 2023 SSA Annual Meeting (Adeboboye et al., 2023). Our objective is to gain insights into the local crustal stresses and orientations of fault slips at depth. This begins with applying a modified workflow for building earthquake catalogs (Neves et al., 2023) to additional data from our recent experiment. Following this, we obtain focal mechanisms of the area, and constrain their solutions using relative S/P amplitude ratios (Skoumal et al., 2023). Subsequently, we will use the focal mechanism solutions, combined with earlier results (e.g., Chapman et al. 2016, Adeboboye et al. 2023), to invert for the local stress inversion (Hardebeck & Michael, 2006). We expect that these efforts will provide insights into the source fault of the 1886 earthquake and its connection to present seismicity.

Session: Tectonics and Seismicity of Stable Continental Interiors [Poster Session]

Type: Poster

Room: Exhibit Hall

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Oluwaseyifunmi Adeboboye

Student Presenter: Yes

Additional Authors