The Mw 5.1, 9 August 2020, Sparta Earthquake, North Carolina: The First Documented Seismic Surface Rupture in the Eastern United States

Paula M. Figueiredo; Jesse S. Hill; Arthur J. Merschat; Corey M. Scheip; Kevin G. Stewart; Lewis A. Owen; Richard M. Wooten; Mark W. Carter; Eric Szymanski; Stephen P. Horton; Karl W. Wegmann; Del Wayne R. Bohnenstiehl; Gary W. Thompson; Anne Witt; Bart Cattanach; Thomas Douglas

doi:10.1130/GSATG517A.1

The M_w 5.1, 9 August 2020, Sparta Earthquake, North Carolina: The First Documented Seismic Surface Rupture in the Eastern United States

Paula M. Figueiredo
, Jesse S. Hill
, Arthur J. Merschat
, Corey M. Scheip
, Kevin G. Stewart
, Lewis A. Owen
, Richard M. Wooten
, Mark W. Carter
, Eric Szymanski
, Stephen P. Horton
, Karl W. Wegmann
, Del Wayne R. Bohnenstiehl
, Gary W. Thompson
, Anne Witt
, Bart Cattanach
, Thomas Douglas

Research output: Contribution to journal › Article › peer-review

40 Scopus citations

Abstract

At 8:07 a.m. EDT on 9 Aug. 2020 a M_w 5.1 earthquake located ~3 km south of Sparta, North Carolina, USA, shook much of the eastern United States, producing the first documented surface rupture due to faulting east of the New Madrid seismic zone. The co-seismic surface rupture was identified along a 2-km-long traceable zone of predominantly reverse displacement, with folding and flexure generating a scarp averaging 8–10-cm-high with a maximum observed height of ~25 cm. Widespread deformation south of the main surface rupture includes cm-dm–long and mm-cm–wide fissures. Two trenches excavated across the surface rupture reveal that this earthquake propagated to the surface along a preexisting structure in the shallow bedrock, which had not been previously identified as an active fault. Surface ruptures by faulting are rarely reported for M <6 earthquakes, and hence the Sparta earthquake provides an opportunity to improve seismic hazard knowledge associated with these moderate events. Furthermore, this earthquake occurred in a very low strain rate intraplate setting, where earthquake surface deformation, regardless of magnitude, is sparse in time and rare to observe and characterize.

Original language	English
Pages (from-to)	4-11
Number of pages	8
Journal	GSA Today
Volume	32
Issue number	3-4
DOIs	https://doi.org/10.1130/GSATG517A.1
State	Published - Mar 2022

Funding

This manuscript is submitted for publication by Charles Gertler, 2020–2021 GSA-USGS Congressional Science Fellow, with the understanding that the U.S. government is authorized to reproduce and distribute reprints for governmental use. The one-year fellowship is supported by GSA and the U.S. Geological Survey, Department of the Interior, under Assistance Award No. G20AP00106. The views and conclusions contained in this document are those of the author and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. government. Gertler worked in the office of Sen. Edward Markey (D-MA) and can be contacted by email at [email protected]. This award recognizes innovative and effective teaching in college-level earth science. Earth-science instructors and faculty members from any academic institution engaged in undergraduate education who have been teaching full-time for 10 years or fewer are eligible (part-time teaching is not counted in this requirement). Both peer-and self-nominations will be accepted. This award, administered by the GSA Foundation, is made possible by support from the Donald and Carolyn Biggs Fund, the GSA Geoscience Education Division, and GSA’s Education and Outreach Program. An additional travel reimbursement is also available to the recipient to enable him or her to attend the award presentation at the GSA annual meeting. https:// community.geosociety.org/gedivision/awards/biggsaward We thank the National Science Foundation for supporting this research (EAR-2102530, support from Tectonics, Geomorphology and Land Use Dynamics, and the Geophysics programs) and the people of Alleghany County in North Carolina for providing access to their lands, particularly Ann Downing and the business owners within the Greenway Drive industrial park. U.S. Geological Survey research supported by the National Cooperative Geologic Mapping Program and Earthquake Hazards Program. Thanks to Sarah Wells and Ashley Lynn for field assistance and Daria Khashchevskaya for help with graphics, and to Thomas Pratt and J. Wright Horton, Jr., and two anonymous reviewers for their comments, which greatly improved this manuscript. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. government.

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Figueiredo, P. M., Hill, J. S., Merschat, A. J., Scheip, C. M., Stewart, K. G., Owen, L. A., Wooten, R. M., Carter, M. W., Szymanski, E., Horton, S. P., Wegmann, K. W., Bohnenstiehl, D. W. R., Thompson, G. W., Witt, A., Cattanach, B., & Douglas, T. (2022). The M_w 5.1, 9 August 2020, Sparta Earthquake, North Carolina: The First Documented Seismic Surface Rupture in the Eastern United States. GSA Today, 32(3-4), 4-11. https://doi.org/10.1130/GSATG517A.1

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title = "The Mw 5.1, 9 August 2020, Sparta Earthquake, North Carolina: The First Documented Seismic Surface Rupture in the Eastern United States",

abstract = "At 8:07 a.m. EDT on 9 Aug. 2020 a Mw 5.1 earthquake located \textasciitilde{}3 km south of Sparta, North Carolina, USA, shook much of the eastern United States, producing the first documented surface rupture due to faulting east of the New Madrid seismic zone. The co-seismic surface rupture was identified along a 2-km-long traceable zone of predominantly reverse displacement, with folding and flexure generating a scarp averaging 8{\textendash}10-cm-high with a maximum observed height of \textasciitilde{}25 cm. Widespread deformation south of the main surface rupture includes cm-dm{\textendash}long and mm-cm{\textendash}wide fissures. Two trenches excavated across the surface rupture reveal that this earthquake propagated to the surface along a preexisting structure in the shallow bedrock, which had not been previously identified as an active fault. Surface ruptures by faulting are rarely reported for M <6 earthquakes, and hence the Sparta earthquake provides an opportunity to improve seismic hazard knowledge associated with these moderate events. Furthermore, this earthquake occurred in a very low strain rate intraplate setting, where earthquake surface deformation, regardless of magnitude, is sparse in time and rare to observe and characterize.",

author = "Figueiredo, \{Paula M.\} and Hill, \{Jesse S.\} and Merschat, \{Arthur J.\} and Scheip, \{Corey M.\} and Stewart, \{Kevin G.\} and Owen, \{Lewis A.\} and Wooten, \{Richard M.\} and Carter, \{Mark W.\} and Eric Szymanski and Horton, \{Stephen P.\} and Wegmann, \{Karl W.\} and Bohnenstiehl, \{Del Wayne R.\} and Thompson, \{Gary W.\} and Anne Witt and Bart Cattanach and Thomas Douglas",

year = "2022",

month = mar,

doi = "10.1130/GSATG517A.1",

language = "English",

volume = "32",

pages = "4--11",

journal = "GSA Today",

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Figueiredo, PM, Hill, JS, Merschat, AJ, Scheip, CM, Stewart, KG, Owen, LA, Wooten, RM, Carter, MW, Szymanski, E, Horton, SP, Wegmann, KW, Bohnenstiehl, DWR, Thompson, GW, Witt, A, Cattanach, B & Douglas, T 2022, 'The M_w 5.1, 9 August 2020, Sparta Earthquake, North Carolina: The First Documented Seismic Surface Rupture in the Eastern United States', GSA Today, vol. 32, no. 3-4, pp. 4-11. https://doi.org/10.1130/GSATG517A.1

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T2 - The First Documented Seismic Surface Rupture in the Eastern United States

AU - Figueiredo, Paula M.

AU - Hill, Jesse S.

AU - Merschat, Arthur J.

AU - Scheip, Corey M.

AU - Stewart, Kevin G.

AU - Owen, Lewis A.

AU - Wooten, Richard M.

AU - Carter, Mark W.

AU - Szymanski, Eric

AU - Horton, Stephen P.

AU - Wegmann, Karl W.

AU - Bohnenstiehl, Del Wayne R.

AU - Thompson, Gary W.

AU - Witt, Anne

AU - Cattanach, Bart

AU - Douglas, Thomas

PY - 2022/3

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N2 - At 8:07 a.m. EDT on 9 Aug. 2020 a Mw 5.1 earthquake located ~3 km south of Sparta, North Carolina, USA, shook much of the eastern United States, producing the first documented surface rupture due to faulting east of the New Madrid seismic zone. The co-seismic surface rupture was identified along a 2-km-long traceable zone of predominantly reverse displacement, with folding and flexure generating a scarp averaging 8–10-cm-high with a maximum observed height of ~25 cm. Widespread deformation south of the main surface rupture includes cm-dm–long and mm-cm–wide fissures. Two trenches excavated across the surface rupture reveal that this earthquake propagated to the surface along a preexisting structure in the shallow bedrock, which had not been previously identified as an active fault. Surface ruptures by faulting are rarely reported for M <6 earthquakes, and hence the Sparta earthquake provides an opportunity to improve seismic hazard knowledge associated with these moderate events. Furthermore, this earthquake occurred in a very low strain rate intraplate setting, where earthquake surface deformation, regardless of magnitude, is sparse in time and rare to observe and characterize.

AB - At 8:07 a.m. EDT on 9 Aug. 2020 a Mw 5.1 earthquake located ~3 km south of Sparta, North Carolina, USA, shook much of the eastern United States, producing the first documented surface rupture due to faulting east of the New Madrid seismic zone. The co-seismic surface rupture was identified along a 2-km-long traceable zone of predominantly reverse displacement, with folding and flexure generating a scarp averaging 8–10-cm-high with a maximum observed height of ~25 cm. Widespread deformation south of the main surface rupture includes cm-dm–long and mm-cm–wide fissures. Two trenches excavated across the surface rupture reveal that this earthquake propagated to the surface along a preexisting structure in the shallow bedrock, which had not been previously identified as an active fault. Surface ruptures by faulting are rarely reported for M <6 earthquakes, and hence the Sparta earthquake provides an opportunity to improve seismic hazard knowledge associated with these moderate events. Furthermore, this earthquake occurred in a very low strain rate intraplate setting, where earthquake surface deformation, regardless of magnitude, is sparse in time and rare to observe and characterize.

UR - https://www.scopus.com/pages/publications/85127902957

U2 - 10.1130/GSATG517A.1

DO - 10.1130/GSATG517A.1

M3 - Article

AN - SCOPUS:85127902957

SN - 1052-5173

VL - 32

SP - 4

EP - 11

JO - GSA Today

JF - GSA Today

IS - 3-4

ER -

The M_w 5.1, 9 August 2020, Sparta Earthquake, North Carolina: The First Documented Seismic Surface Rupture in the Eastern United States

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