Earthquake · reviewed by a seismologist
M 3.8mb_lg
Earthquake near Helena, OK
No earthquake was likely felt in Helena in the 24 hours to 10:09 am CST (16:09 UTC). The last one was M 3.4, 106 km (66 mi) S, at 5:53 am CST on 7 November 2026, estimated intensity II (weak) in town; 23 felt reports to USGS. Every earthquake near Helena
This page: a magnitude 3.8 earthquake was recorded 10 km (6 mi) south-southwest of Helena, OK, at 3:25 pm CDT on 21 October 2016 (20:25 UTC), 5.0 km deep.
USGS: 9 km SSW of Helena, Oklahoma
39 km (24 mi) W of Enid, OK · 132 km (82 mi) NNW of Oklahoma City, OK
- When
- 3:25 pm CDT on 21 October 2016 ()
- Where
- 10 km (6 mi) south-southwest of Helena, OK · earthquakes near Helena
- Oklahoma today
- every earthquake in Oklahoma in the last 24 hours
- Magnitude
- M 3.8 (mb_lg)
- Depth
- 5.0 km below the surface
- Felt
- no reports yet
- Measured shaking
- intensity IV (ShakeMap)
- Nearest
- Major County, 27 km SW
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 3583 days ago
Earthquake alerts for Helena, OK
Get a notification in this browser when USGS records an earthquake near Helena, OK. 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 small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.
At this magnitude and depth, people at rest would likely notice it out to about 401 km (249 mi) from the epicentre. In Helena, 10 km away, the estimate is intensity IV (light). 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.
Likely felt in: Helena 10 km, intensity IV · Fairview 27 km, intensity IV · Cherokee 33 km, intensity III · Okeene 39 km, intensity III · Enid 39 km, intensity III · Alva 50 km, intensity III. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 7.6 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.8 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 22,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 1,000× the energy of this one
- Magna, Utah 2020 M 5.7 710× the energy of this one
- This earthquake M 3.8 about 7.6 tons of TNT
- Around the size people start to feel M 3.0 this one released 16× more
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
The largest earthquake within 50 km since 2016 was M 5.1 on 2016-02-13 — about 89 times the energy of this one.
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 36.4642, -98.3036. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Major County, OK | 27 km (17 mi) | SW | earthquakes near Major County |
| Alfalfa County, OK | 30 km (18 mi) | N | earthquakes near Alfalfa County |
| Garfield County, OK | 47 km (29 mi) | ESE | earthquakes near Garfield County |
| Woods County, OK | 58 km (36 mi) | WNW | earthquakes near Woods County |
| Grant County, OK | 58 km (36 mi) | NE | earthquakes near Grant County |
| Kingfisher County, OK | 66 km (41 mi) | SSE | earthquakes near Kingfisher County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
59 earthquakes have been recorded within 50 km since this one.
- 2.6 4 km SW of Cherokee, Oklahoma
- 2.5 17 km SSE of Waynoka, Oklahoma
- 2.5 17 km SE of Waynoka, Oklahoma
- 2.5 17 km SSE of Waynoka, Oklahoma
- 2.5 17 km SSE of Waynoka, Oklahoma
- 2.9 17 km SSE of Waynoka, Oklahoma
- 2.8 17 km SSE of Waynoka, Oklahoma
- 2.7 4 km NE of Meno, Oklahoma
- 2.7 17 km SSE of Waynoka, Oklahoma
- 2.9 17 km SE of Waynoka, Oklahoma
- 2.5 12 km WSW of Cleo Springs, Oklahoma
- 2.7 16 km SE of Waynoka, Oklahoma
- 2.7 5 km N of Lambert, Oklahoma
- 2.6 16 km SSE of Waynoka, Oklahoma
- 3.0 17 km SSE of Waynoka, Oklahoma
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.