Earthquake · reviewed by a seismologist
M 2.4md
Earthquake near O'Fallon, IL
No earthquake was likely felt in O'Fallon in the 24 hours to 4:34 am CST (10:34 UTC). The last one was M 3.5, 170 km (105 mi) E, at 2:05 am CDT on 29 June 2026, estimated intensity II (weak) in town; 392 felt reports to USGS. Every earthquake near O'Fallon
This page: a magnitude 2.4 earthquake was recorded in O'Fallon, IL, at 1:50 am CDT on 27 July 2024 (06:50 UTC), less than 1 km deep. 26 people have reported feeling it to USGS.
USGS: 1 km SSW of O'Fallon, Illinois
29 km (18 mi) ESE of St. Louis, MO
- When
- 1:50 am CDT on 27 July 2024 ()
- Where
- in O'Fallon, IL · earthquakes near O'Fallon
- Illinois today
- every earthquake in Illinois in the last 24 hours
- Magnitude
- M 2.4 (md)
- Depth
- 0.3 km below the surface
- Felt
- 26 reports · strongest reported intensity IV
- Nearest
- St. Clair County, 12 km S
- Nearest mapped fault
- St. Louis-Cape Girardeau liquefaction features, 4 km from its surface trace — near is not the same as on
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 651 days ago
Earthquake alerts for O'Fallon, IL
Get a notification in this browser when USGS records an earthquake near O'Fallon, IL. No account or email needed.
Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.
At this magnitude and depth, people at rest would likely notice it out to about 40 km (25 mi) from the epicentre. Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.
Earthquakes near other towns within 30 km: Shiloh, Fairview Heights, Scott Air Force Base, Swansea, Belleville, Lebanon.
How big was it?
This earthquake released about 110 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.4 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 140,000× the energy of this one
- Magna, Utah 2020 M 5.7 99,000× the energy of this one
- Around the size people start to feel M 3.0 8.8× the energy of this one
- This earthquake M 2.4 about 110 lb of TNT
Energy from the Gutenberg–Richter relation (log10E = 1.5M + 4.8), rounded to two figures; bar length is magnitude, which is already a logarithm of energy. Magnitudes of past earthquakes from the USGS catalogue.
For this area
No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.
Before 2016, the USGS record since 1900 lists no earthquake of M5 or more within 50 km.
Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.
Where
Epicentre 38.5815, -89.9193. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| St. Clair County, IL | 12 km (8 mi) | S | earthquakes near St. Clair County |
| Madison County, IL | 27 km (17 mi) | N | earthquakes near Madison County |
| St. Louis city, MO | 29 km (18 mi) | WNW | earthquakes near St. Louis city |
| Monroe County, IL | 41 km (25 mi) | SW | earthquakes near Monroe County |
| Clinton County, IL | 43 km (27 mi) | E | earthquakes near Clinton County |
| St. Louis County, MO | 46 km (29 mi) | W | earthquakes near St. Louis County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
3 earthquakes have been recorded within 50 km since this one.
- 2.4 3 km ESE of Fenton, Missouri
- 2.3 4 km S of Valmeyer, Illinois
- 2.3 4 km E of Herculaneum, Missouri
Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of . QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.
On USGS
- The official USGS event page — the source of record for every value above
- Did you feel it? Report it to USGS — reports go to USGS, not to us
- ShakeMap for this event, when USGS has produced one
QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.