Earthquake · reviewed by a seismologist
M 3.3ml
Earthquake near Blackwell, OK
No earthquake was likely felt in Blackwell in the 24 hours to 10:48 am CST (16:48 UTC). The last one was M 3.4, 149 km (93 mi) SSW, at 5:53 am CST on 7 November 2026, estimated intensity II (weak) in town; 23 felt reports to USGS. Every earthquake near Blackwell
This page: a magnitude 3.3 earthquake was recorded 37 km (23 mi) west of Blackwell, OK, at 5:43 am CDT on 27 July 2018 (10:43 UTC), 6.9 km deep. 3 people have reported feeling it to USGS.
USGS: 5 km NE of Medford, Oklahoma
99 km (61 mi) SSW of Wichita, KS · 51 km (32 mi) NNE of Enid, OK
- When
- 5:43 am CDT on 27 July 2018 ()
- Where
- 37 km (23 mi) west of Blackwell, OK · earthquakes near Blackwell
- Oklahoma today
- every earthquake in Oklahoma in the last 24 hours
- Magnitude
- M 3.3 (ml)
- Depth
- 6.9 km below the surface
- Felt
- 3 reports · strongest reported intensity IV
- Nearest
- Grant County, 10 km SW
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1556 days ago
Earthquake alerts for Blackwell, OK
Get a notification in this browser when USGS records an earthquake near Blackwell, 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 234 km (145 mi) from the epicentre. In Blackwell, 37 km away, the estimate is intensity III (weak). 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: Caldwell 22 km, intensity III · Blackwell 37 km, intensity III · Anthony 45 km, intensity III. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 1.3 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.3 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 130,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 5,600× the energy of this one
- Magna, Utah 2020 M 5.7 4,000× the energy of this one
- This earthquake M 3.3 about 1.3 tons of TNT
- Around the size people start to feel M 3.0 this one released 2.8× 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 4.4 on 2018-06-09 — about 45 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 36.8475, -97.6964. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Grant County, OK | 10 km (7 mi) | SW | earthquakes near Grant County |
| Sumner County, KS | 47 km (29 mi) | NNE | earthquakes near Sumner County |
| Kay County, OK | 49 km (31 mi) | E | earthquakes near Kay County |
| Harper County, KS | 50 km (31 mi) | NW | earthquakes near Harper County |
| Garfield County, OK | 53 km (33 mi) | S | earthquakes near Garfield County |
| Alfalfa County, OK | 57 km (36 mi) | WSW | earthquakes near Alfalfa County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
56 earthquakes have been recorded within 50 km since this one.
- 2.7 10 km ESE of Jefferson, Oklahoma
- 2.6 10 km W of Lamont, Oklahoma
- 1.5 11 km SE of Mayfield, Kansas
- 1.9 11 km SE of Mayfield, Kansas
- 3.0 11 km SE of Mayfield, Kansas
- 2.2 11 km SE of Mayfield, Kansas
- 2.1 11 km SE of Mayfield, Kansas
- 2.6 11 km SW of Wellington, Kansas
- 1.6 11 km SE of Mayfield, Kansas
- 1.7 11 km SE of Mayfield, Kansas
- 2.8 11 km SE of Mayfield, Kansas
- 2.8 11 km SE of Mayfield, Kansas
- 2.2 11 km SE of Mayfield, Kansas
- 1.7 11 km SE of Mayfield, Kansas
- 2.3 11 km SE of Mayfield, Kansas
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.