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)[1]
Epicenter36°28′34″N 81°05′35″W / 36.476°N 81.093°W / 36.476; -81.093
TypeOblique-slip reverse[2]
Areas affectedNorth Carolina, Virginia
Total damageAt least $24,000,000 USD[3]
Max. intensityVII (Very strong)[4]
Landslides0 (none reported)
Foreshocks8[5]
Aftershocks11 (as of 8/11/20 1:00 a.m. EDT)[6]
Casualties1 injured[7][8]

The 2020 Sparta earthquake was a relatively uncommon intraplate earthquake that occurred near the small town of Sparta, North Carolina, on August 9, 2020 at 8:07 am local time. The earthquake had a moment magnitude of 5.1, and a shallow depth of 7.6 kilometers (4.7 mi).[2] Shaking was reported throughout the Southern, Midwestern, and Northeastern United States.[9] It was the strongest earthquake recorded in North Carolina in 104 years,[10] the second-strongest in the state's history,[11] and the largest to strike the East Coast since the 2011 Virginia earthquake.[12][13]

Geology

The earthquake occurred near the Piedmont region and Blue Ridge Mountains, part of the eastern Appalachian Mountain range which formed due to an ancient continental collision with the African Plate roughly 480 million years ago during the Ordovician period.[14] Many thrust faults were formed during this time as the mountain grew in size. When Pangea broke up, the uplift of the Appalachians ultimately ceased, leading to increased erosion rates due to the steep terrain.[15][16] Ever since, the mountains have been gradually diminishing in size to their current state today. The mountains also played a role in where the quake was felt, with "DYFI" reports sharply decreasing west of the Appalachians.

Erosion carries sediments out of the mountains and down towards the Atlantic Ocean (on the east side) and the Gulf of Mexico (on the west). This movement of sediment can alleviate the pressure of overlying rocks and cause ancient faults (once active during the mountain building processes) to reactivate and create earthquakes. It is believed this is a factor in the 2020 Sparta earthquake as well as others in the region such as the 2011 Virginia earthquake.[citation needed]

The area of the earthquake is located marginally within the Eastern Tennessee Seismic Zone.[17] The ETSZ is responsible for a number of moderate-sized earthquakes in the past, with the last notable earthquake occurring in eastern Tennessee in 2018.

Earthquake

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

The focal mechanism for the earthquake suggest oblique-reverse faulting on either a northwest, or south-striking fault.[18][2] It produced "Very strong" shaking,[19] and over 100,000 reported feeling it.[20]

Foreshocks

There were 8 foreshocks ranging from Md1.8 to 2.6, the earliest of which was a Md2.1 that occurred on August 8, one day prior to the 5.1 mainshock.[5]

Aftershocks

The strongest aftershock of the sequence was a Md2.9 that struck 2 days after the mainshock. In total, there were 20 recorded aftershocks as of August 27, 2020.[21][22]

Impacts

Damage

Widespread damage occurred in Sparta, which had already been debilitated by the COVID-19 pandemic in North Carolina.[23] Damages include collapsed ceilings, chimneys, and masonry; damaged water mains; cracked and deformed roads; uprooted headstones; and displaced appliances and items.[24][23][25] Wes Brinegar, the town's mayor, issued a state of emergency to apply for FEMA and state financial aid.[25][23] Damage was worse than initially thought, with at least 525 structures being damaged, and 60 with major damage, meaning at least 40% of the structure was a total loss. 19 people lost their homes, 25 were declared uninhabitable, and scammers took advantage of the damage, charging people up to $500 USD for repairs, but never showing up.[26]

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."[27]

Injuries

There were no fatalities. A boy in Sparta who was cut by a falling picture frame was the only reported injury.[7][8]

Scientific discoveries

An academic paper published in December 2022 found that a 1.5-mile-long (2.4 km) crack had been created in the surface of the Earth, southeast of Sparta, as a result of the quake.[28] The crack exposed a previously unknown fault line, dubbed the Little River Fault. The crack features a vertical scarp, or drop-off, of 9 inches at its tallest point. Because of these findings, researchers identified the earthquake as the first ever documented surface rupture earthquake in the Eastern United States. It was additionally noted that earthquakes of such magnitude as the Sparta earthquake rarely cause surface ruptures.[29]

Some damage caused by the earthquake was linked to the rupture; it was found to have caused the buckling of a local road, damage to water lines, and damage to several properties.[28]

See also

References

  1. ^ "M 5.1 - 4 km SE of Sparta, North Carolina". United States Geological Survey. Archived from the original on December 11, 2020. Retrieved August 12, 2020.
  2. ^ a b c "USGS M 5.1 main page". earthquake.usgs.gov. Retrieved August 9, 2020.
  3. ^ 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.
  4. ^ "USGS ShakeMap products from M 5.1 event". earthquake.usgs.gov. Retrieved August 9, 2020.
  5. ^ a b "USGS foreshocks of M 5.1 event". earthquake.usgs.gov. Retrieved August 9, 2020.
  6. ^ "USGS aftershocks of M 5.1 event". earthquake.usgs.gov. Retrieved August 9, 2020.
  7. ^ a b "Powerful 5.1 magnitude earthquake jolts Charlotte area, strongest in NC in 104 years".
  8. ^ a b Perez, 7, has the only reported injury in Sparta. He was in bed, felt the quake and ran when a picture frame fell on him. The glass cut his knee but he was excited to show us his bandaid
  9. ^ "USGS DYFI reports from M 5.1 event". earthquake.usgs.gov. Retrieved August 9, 2020.
  10. ^ "5.1 magnitude earthquake reported near North Carolina-Virginia border". ABC News. Retrieved August 9, 2020.
  11. ^ "USGS largest earthquakes in North Carolina since record-keeping". earthquake.usgs.gov. Retrieved August 11, 2020.
  12. ^ "5.1 Magnitude Earthquake Rattles North Carolina, South Carolina, Virginia, Tennessee; Roads cracked, dishes broken". The Weather Channel. Retrieved August 9, 2020.
  13. ^ "USGS East Coast earthquakes M 5+ since record-keeping". earthquake.usgs.gov. Retrieved August 9, 2020.
  14. ^ "Geologic Provinces of the United States: Appalachian Highlands Province". USGS. Archived from the original on March 11, 2013. Retrieved July 19, 2010.
  15. ^ "The Mountains That Froze the World". AAAS. November 3, 2009. Retrieved April 4, 2012.
  16. ^ "Geology of the Great Smoky Mountains". usgs. Archived from the original on January 17, 2013. Retrieved April 4, 2012.
  17. ^ Sunday's earthquake should serve as warning in preparedness on YouTube. WLOS (user ABC13Channel). August 10, 2020.
  18. ^ "USGS Technical Summary". earthquake.usgs.gov. Retrieved August 11, 2020.
  19. ^ "ShakeMap intensity". earthquake.usgs.gov. Retrieved August 11, 2020.
  20. ^ ""Did You Feel It?" reports". earthquake.usgs.gov. Retrieved August 11, 2020.
  21. ^ "USGS 2.9 aftershock". earthquake.usgs.gov. Retrieved August 12, 2020.
  22. ^ "Residents Still Cleaning Up In Sparta". spectrumlocalnews.com. Retrieved August 27, 2020.
  23. ^ a b c "NC officials survey earthquake damage in Sparta, look for ways to rebuild". myfox8.com. August 11, 2020. Retrieved August 11, 2020.
  24. ^ "People still rattled after North Carolina earthquake that caused significant damage". WAVY.com. August 10, 2020. Retrieved August 11, 2020.
  25. ^ a b WTVD (August 10, 2020). "Multiple aftershocks felt around western NC following 5.1 magnitude earthquake". ABC11 Raleigh-Durham. Retrieved August 11, 2020.
  26. ^ "525 buildings damaged | Sparta earthquake destruction worse than initially thought, emergency officials say". wcnc.com. August 18, 2020. Retrieved August 27, 2020.
  27. ^ "Gov. Roy Cooper visits Sparta homes, businesses to assess earthquake damage". wcnc.com. August 11, 2020. Retrieved August 27, 2020.
  28. ^ 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.
  29. ^ "What the Sparta Earthquake Tells Us About Shallow Quakes". NC State News. March 29, 2022. Retrieved October 13, 2023.

Further reading

External links

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