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2020 Sparta earthquake

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Coordinates: 35°45′58″N 117°36′18″W / 35.766°N 117.605°W / 35.766; -117.605
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35°45′58″N 117°36′18″W / 35.766°N 117.605°W / 35.766; -117.605

2020 Sparta earthquake
2020 Sparta earthquake is located in North Carolina
Sparta
Sparta
Raleigh
Raleigh
Charlotte
Charlotte
Greensboro
Greensboro
2020 Sparta earthquake
UTC time2020-08-09 12:07:37
ISC event618711487
USGS-ANSSComCat
Local dateAugust 9, 2020 (2020-08-09)
Local time8:07:47 a.m. EDT
MagnitudeMw5.1
Depth7.6 km (4.7 mi)
Epicenter36°28′34″N 81°05′35″W / 36.476°N 81.093°W / 36.476; -81.093
FaultLittle River Fault
TypeOblique-slip reverse
Areas affectedNorth Carolina, Virginia
Max. intensityMMI VII (Very strong)
ForeshocksYes
AftershocksYes
CasualtiesMinor injuries

The 2020 Sparta earthquake was a relatively uncommon intraplate earthquake that occurred near the small town of Sparta, North Carolina, on August 9 at 08:07 ET. The thrust-faulting earthquake had a moment magnitude of 5.1, and a shallow depth of 7.6 kilometers (4.7 mi). Rupture occurred on the previously unmapped Little River Fault. Shaking was reported in parts of the Midwestern, and Southeastern United States. It was the strongest earthquake recorded in North Carolina in 104 years,[1] the second-strongest in the state's history, and the largest to strike the East Coast since the 2011 Virginia earthquake.[2][3] A surface rupture was documented following the earthquake; the first of its kind in the Eastern United States.

Earthquake[edit]

Illustrations depicting the movement of normal and reverse faults. The 2020 Sparta earthquake's movement was reverse (right image).
DYFI ("Did You Feel It?") responses showing perceived shaking intensity

Measuring Mw  5.1, it was the state's largest earthquake since a magnitude 5.2 earthquake struck Skyland in 1916. Over 80,000 people reported shaking from the earthquake.[4]

Tectonic setting[edit]

The earthquake occurred near the Piedmont region and Blue Ridge Mountains, part of the eastern Appalachian Mountains which formed due to an ancient continental collision with the African Plate, during the Ordovician period, roughly 480 million years ago. This led to the formation of a supercontinent known as Pangaea.[5] During the orogeny, many thrust faults were formed. Continental collision extended for the next 250 million years, forming the Caledonian, Acadian, Ouachita, Hercynian, and Allegheny orogenies. When Pangaea broke up beginning in the Early Mesozoic, uplifting of the Appalachians ceased, leading to increased erosion rates due to the steep terrain. Another period of uplifting the eroded topography occurred during the Cenozoic Era which led to aggressive erosion by rivers and streams.[5][6][7]

The mainshock source area was in the Blue Ridge Mountains of the Alleghanian orogeny. Faults in this part of the range typically trend northeast. The earthquake ruptured along a fault trend that is consistent with west–northwest to east–west striking structures that crosses major northeast-trending geological structures of the mountain range. However, the geology of these faults are poorly understood. The earthquake occurred in a region that progresses between thrust and strike-slip tectonics; the dominant crustal strain is configured in a northeast–southwest to east-northeast–west-southwest direction.[8]

Geology[edit]

According to the United States Geological Survey, the mainshock was the result of oblique-reverse faulting within the shallow crust of the North American Plate. The focal mechanism solutions for the earthquake indicate rupture occurred on a moderately dipping fault either striking to the northwest or south. This earthquake occurred in the interior of the plate, known as an intraplate earthquake. Four aftershocks of magnitudes between 2.1 and 2.6 were recorded beginning about 25 hours prior to the earthquake.[9] The strongest of the sequence was a Md2.9 aftershock that struck two days after the mainshock.[10] There were 20 recorded aftershocks by August 28.[11] In Sparta, it had an estimated maximum Modified Mercalli intensity of VI–VII and the peak ground acceleration exceeded 0.2 g.[12]

A 1.5 mi (2.4 km) surface rupture associated with the earthquake was discovered southeast of Sparta.[13] The fracture exposed a previously unmapped fault, dubbed the Little River Fault. Trenching of the Little River Fault indicate it is a thrust fault with at least 10 cm (3.9 in) of displacement. This west-northwest–east-southeast striking fault slices through the local Paleozoic rocks.[14] It featured a vertical scarp, or drop-off, of 9 in (230 mm) at its highest point. It was the first ever documented surface rupture from an earthquake in the Eastern United States,[15] and the second observation made in Eastern North America.[8] The rupture buckled a local road, damaged water lines, and several properties.[13]

Damage[edit]

Widespread damage occurred in Sparta, which had already been debilitated by the COVID-19 pandemic in North Carolina.[16] The town's manager, Ryan Wilmoth, said there were "very minor injuries" but did not specify the number of people injured.[4] Within a week of the earthquake, there were 60 cases of serious damage and 465 minor damage reports.[17] Nineteen people lost their homes and 25 were declared uninhabitable.[18] Damage include collapsed ceilings, chimneys, and masonry; damaged water mains; cracked and deformed roads; uprooted headstones; and displaced appliances and items.[19][16][20] The earthquake was felt in Washington D.C., Atlanta, and parts of Tennessee and Ohio.[21][22]

Aftermath[edit]

Wes Brinegar, the town's mayor, issued a state of emergency to apply for FEMA and state financial aid.[20][16] At least $112 thousand in state assistance grants were handed out to the affected. The Small Business Administration issued $1.17 million in loans. As the earthquake and its aftermath did not meet FEMA's disaster assistance criteria, the legislature of North Carolina allocated $24 million for relief. The project and its funding established a three-year project, Earthquake Recovery Program, operated by the Office of State Budget and Management and North Carolina Emergency Management.[23] By 2021, there were over 230 requests for home repair assistance, averaging $44 thousand per home.[24]

Brinegar also cautioned residents of scams on GoFundMe as officials did not raise any request on the site.[17] Scammers took advantage of the damage, charging people up to $500 for repairs and failing to show up.[18] Governor of North Carolina, Roy Cooper, toured the damage in Sparta, releasing a statement later, stating "We’ve dealt with a hurricane, a violent tornado, and now an earthquake all in the middle of a pandemic: North Carolinians are resilient."[25]

See also[edit]

References[edit]

  1. ^ "5.1 magnitude earthquake reported near North Carolina-Virginia border". ABC News. Retrieved August 9, 2020.
  2. ^ "5.1 Magnitude Earthquake Rattles North Carolina, South Carolina, Virginia, Tennessee; Roads cracked, dishes broken". The Weather Channel. Retrieved August 9, 2020.
  3. ^ "Search earthquake catalog", United States Geological Survey (Data base), retrieved August 9, 2020
  4. ^ a b Price, Mark; Lindstrom, Lauren. "Powerful 5.1 magnitude earthquake jolts Charlotte area, strongest in NC in 104 years". The Charlotte Observer.
  5. ^ a b "Geologic Provinces of the United States: Appalachian Highlands Province". United States Geological Survey. Archived from the original on March 11, 2013. Retrieved July 19, 2010.
  6. ^ "The Mountains That Froze the World". AAAS. November 3, 2009. Retrieved April 4, 2012.
  7. ^ "Geology of the Great Smoky Mountains". usgs. Archived from the original on January 17, 2013. Retrieved April 4, 2012.
  8. ^ a b Neves, Miguel; Chuang, Lindsay Y.; Li, Wei; Peng, Zhigang; Figueiredo, Paula M.; Ni, Sidao (2024). "Complex rupture dynamics of the extremely shallow August 2020 M5.1 Sparta, North Carolina earthquake". Communications Earth & Environment. 5 (163). doi:10.1038/s43247-024-01316-8.
  9. ^ ANSS. "M 5.1 - 4 km SE of Sparta, North Carolina 2020". Comprehensive Catalog. U.S. Geological Survey. Public Domain This article incorporates text from this source, which is in the public domain.
  10. ^ ANSS. "M 2.9 - 3 km SSE of Sparta, North Carolina 2020". Comprehensive Catalog. U.S. Geological Survey.
  11. ^ "Residents Still Cleaning Up In Sparta". spectrumlocalnews.com. Retrieved August 27, 2020.
  12. ^ Figueiredo, Paula; Hill, Jesse; Merschat, Arthur; Scheip, Corey; Stewart, Kevin; Owen, Lewis; Wooten, Richard; Carter, Mark; Szymanski, Eric; Horton, Stephen; Wegmann, Karl; Bohnenstiehl, DelWayne; Thompson, Gary; Witt, Anne; Cattanach, Bart (March 2022). "The Mw 5.1, 9 August 2020, Sparta Earthquake, North Carolina: The First Documented Seismic Surface Rupture in the Eastern United States". The Geological Society of America Today. 32 (3–4): 4–11. Bibcode:2022GSAT...32....4F. doi:10.1130/GSATG517A.1. S2CID 246323176 – via GSA Today.
  13. ^ a b Price, Mark (December 8, 2022). "Crack in ground more than 1.5 miles long found at site of 2020 quake in North Carolina". The Charlotte Observer. Retrieved October 13, 2023.
  14. ^ Merschat, Arthur J.; Carter, Mark W. (2023). "Preliminary Map of the Surface Rupture From the August 9, 2020, Mw 5.1 Earthquake Near Sparta, North Carolina—The Little River Fault and Other Possible Coseismic Features". U.S. Geological Survey Open-File Report 2023–1074, 1 sheet, scale 1:24,000. doi:10.3133/ofr20231074. Retrieved July 12, 2024.Public Domain This article incorporates text from this source, which is in the public domain.
  15. ^ "What the Sparta Earthquake Tells Us About Shallow Quakes". NC State News. March 29, 2022. Retrieved October 13, 2023.
  16. ^ a b c Kabba, Rasheeda (August 11, 2020). "NC officials survey earthquake damage in Sparta, look for ways to rebuild". WGHP. Retrieved August 11, 2020.
  17. ^ a b Eiklor, Rose (August 18, 2020). "Residents Still Cleaning Up In Sparta". Spectrum News. Retrieved July 12, 2024.
  18. ^ a b "525 buildings damaged: Sparta earthquake destruction worse than initially thought, emergency officials say". wcnc.com. August 18, 2020. Retrieved August 27, 2020.
  19. ^ "People still rattled after North Carolina earthquake that caused significant damage". WGHP. WAVY-TV. August 10, 2020. Retrieved August 11, 2020.
  20. ^ a b "Multiple aftershocks felt around western NC following 5.1 magnitude earthquake". WTVD. ABC11 Raleigh-Durham. August 10, 2020. Retrieved August 11, 2020.
  21. ^ McLaughlin, Eliott C.; Johnston, Chuck (August 9, 2020). "North Carolina's strongest earthquake in 94 years shakes area along Virginia border". CNN. Retrieved July 13, 2024.
  22. ^ Cappucci, Matthew (August 9, 2020). "5.1-magnitude earthquake strikes North Carolina, is felt hundreds of miles away". The Washington Post. Retrieved July 13, 2024.
  23. ^ Evans, Marcia (August 9, 2021). "One Year After Sparta Earthquake, Recovery is Well Underway". Office of State Budget and Management. Retrieved July 12, 2024.
  24. ^ Allman, Megan (August 9, 2021). "Sparta earthquake: 1 year since 5.1 magnitude earthshaker". WFMY-TV. Retrieved July 13, 2024.
  25. ^ "Gov. Roy Cooper visits Sparta homes, businesses to assess earthquake damage". wcnc.com. August 11, 2020. Retrieved August 27, 2020.

Further reading[edit]

External links[edit]

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