M3.3 Earthquake near South Carolina — September 27, 2021
2021-09-27 22:21:57 UTC (2021-09-27) · approx. 5:21 PM UTC-5 local
Felt by 2,806 people across a wide area. Maximum shaking intensity MMI 4.0 (moderate).
On September 27, 2021 at 22:21 UTC, a magnitude 3.3 shallow crustal earthquake struck near South Carolina, at a depth of 6.8 km and coordinates 32.9440°, -80.1540°. The earthquake was reported felt by 2,806 peopleacross a wide area, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 4.0 (moderate). This earthquake was detected by 17 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 705, making it a moderate-impact event.
Physical scale: An earthquake of magnitude 3.3 releases seismic energy equivalent to roughly 1.2 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 109 m — a useful intuition for the size of the slip patch on the fault.
The epicenter is located in South Carolina, a region characterized by the Middleton Place-Summerville Seismic Zone near Charleston, site of the destructive 1886 M7.3 earthquake. View all earthquakes in South Carolina.
Learn more: Magnitude scale · Aftershock sequences
What the Shaking Felt Like
At MMI 4.0 (moderate), people in the most strongly affected areas would have experienced: Mild shaking, similar to a passing truck. Hanging objects swing. Glasses and dishes may rattle. Not commonly felt outdoors.
ShakeMap — predicted shaking intensity
Modeled ground-motion intensity contoured on the Modified Mercalli scale (MMI). Computed by the USGS from the moment-tensor solution and regional ground-motion prediction equations.
Source: U.S. Geological Survey ShakeMap. View interactive ShakeMap on USGS
Did You Feel It? — community-reported shaking
Aggregated felt-report intensity from 2,806 citizen responses to the USGS Did You Feel It? system. Each colored zone represents the average MMI from reports in that area.
Source: U.S. Geological Survey Did You Feel It?. View on USGS · submit your own report
Earthquake Details
-80.1540°E
Technical Information
Common Questions
How strong was the magnitude 3.3 earthquake near South Carolina?
The magnitude 3.3 earthquake that struck near South Carolina on September 27, 2021 at 22:21 UTC had a depth of 6.8 km. It was felt by 2,806 people with maximum shaking intensity of MMI 4.0 (moderate). For context, this was a minor earthquake typically detected only by instruments.
Where did the earthquake occur?
The earthquake epicenter was located at 32.9440°, -80.1540°, which is near South Carolina. View all earthquakes in South Carolina.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 3.3 earthquakes can continue for several days and gradually diminish over time.
Has South Carolina had earthquakes this big before?
The largest recorded earthquake in South Carolina was the M7.3 Charleston earthquake of August 31, 1886. Today's magnitude 3.3 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: se60370971). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, September 27, 2021). M3.3 Earthquake near South Carolina — September 27, 2021. Retrieved December 20, 2021 from https://www.earthquaketracker.org/earthquakes/event/se60370971/