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Dealing With the Unexpected: South Carolina’s Response to the 2021-2022 Elgin-Lugoff Earthquake Sequence

Description: 

Starting with a M=3.3 event on December 27, 2021, the Elgin-Lugoff, South Carolina region has experienced 80 felt events as of December 10, 2022. 19 of these generated 100+ “Did You Feel It (DYFI)?” reports (5 largest generated 1000+) and over 25,000 total DYFI reports resulted from this sequence. A review of historical earthquakes in the Midlands of South Carolina has revealed no evidence of previous seismicity associated with this source zone, making this a clearly “unexcepted” set of events. Multiple organizations in South Carolina responded to this sequence, primarily to inform state/local government agencies and the public regarding the nature and potential hazards associated with these earthquakes. We faced several challenges in doing so, in particular because of a lack of seismic stations near the swarm (closest network station >30 kilometers distance). Only 1 seismometer/telemetry system was initially available to redeploy close to the seismicity, which improved detection and location of events but was not sufficient to clearly delineate the geologic structure associated with this earthquake swarm. On a positive note, moment tensors for the larger (M 3.3-3.6) earthquakes determined by other organization (SLU/USGS) allowed us to quickly determine that these earthquakes were consistent with the regional stress field and not associated with the longer segments of the Eastern Piedmont Fault System that run through the area. This also helped combat public rumors that these events were human-induced and not natural. This earthquake sequence also exposed a vulnerability in earthquake response in South Carolina, in that no state agency had the ability to closely monitor this earthquake sequence adequately and answer all the questions posed by other state/local agencies and the public. Led by the South Carolina Geological Survey, we are currently proposing that the state acquire a set of portable, telemetered instruments that would fill this gap.

Session: Collective Impact in Earthquake Science

Type: Oral

Date: 4/18/2023

Presentation Time: 09:00 AM (local time)

Presenting Author: Steven Jaume

Student Presenter: No

Invited Presentation: 

Authors