The 1886 Charleston, South Carolina, earthquake: Intensities and ground motions

Bulletin of the Seismological Society of America
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Abstract

The 1 September 1886 Charleston, South Carolina, earthquake was one of the largest preinstrumental earthquakes in eastern North America for which extensive contemporaneous observations were documented. The distribution of shaking was mapped shortly after the earthquake, and reconsidered by several authors in the late twentieth century, but has not been reconsidered with a modern appreciation for issues associated with macroseismic data interpretation. Detailed contemporary accounts have also never been used to map the distribution of numerical shaking intensities in the near field. In this study we reconsider macroseismic data from far‐field accounts as well as detailed accounts of damage in the near field, estimating modified Mercalli intensity values at 1297 locations including over 200 definite “not felt” reports that delineate the overall felt extent. We compare the results to the suite of ground‐motion models for eastern North America selected by the National Seismic Hazard Model, using a recently proposed mainshock rupture model and an average site condition for the locations at which intensities are estimated. The comparison supports the moment magnitude estimate, 7.3, from a recently proposed rupture model (Bilham and Hough, 2023). A ShakeMap constrained by model predictions and estimated intensities further illustrates this consistency, which we show is insensitive to rupture model details. Given the uncertainty of calibration relations for magnitudes close to 7, the overall intensity distribution provides a good characterization of shaking but cannot improve the independent moment magnitude estimate. We also identify a previously unrecognized early large aftershock that occurred 9–10 min after the mainshock, for which we estimate magnitude ∼5.6.

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Publication type Article
Publication Subtype Journal Article
Title The 1886 Charleston, South Carolina, earthquake: Intensities and ground motions
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120230224
Volume 114
Issue 3
Publication Date January 17, 2024
Year Published 2024
Language English
Publisher Seismological Society of America
Contributing office(s) Earthquake Science Center
Description 22 p.
First page 1658
Last page 1679
Country United States
State South Carolina
City Charleston
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