QuakeIndex

Earthquake · reviewed by a seismologist

M 2.5ml

Earthquake near Alva, OK

No earthquake was likely felt in Alva in the 24 hours to 11:32 am CST (17:32 UTC). The last one was M 3.4, 144 km (90 mi) SSE, at 5:53 am CST on 7 November 2026, estimated intensity II (weak) in town; 23 felt reports to USGS. Every earthquake near Alva

This page: a magnitude 2.5 earthquake was recorded 31 km (19 mi) south of Alva, OK, at 11:40 am CDT on 20 April 2018 (16:40 UTC), 5.4 km deep.

USGS: 13 km WSW of Carmen, Oklahoma

11:40 am CDT, Apr 20, 2018 · · 5.4 km deep · released about 170 lb of TNT

Every earthquake near Alva Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Major County 25 kmWoods County 32 kmAlfalfa County 33 kmWoodward County 61 kmDewey County 72 kmBlaine County 74 kmGarfield County 75 kmBarber County 77 kmGrant County 78 km
Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.
When
11:40 am CDT on 20 April 2018 ()
Where
31 km (19 mi) south of Alva, OK · earthquakes near Alva
Oklahoma today
every earthquake in Oklahoma in the last 24 hours
Magnitude
M 2.5 (ml)
Depth
5.4 km below the surface
Felt
no reports yet
Nearest
Major County, 25 km SSE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 3040 days ago

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 46 km (29 mi) from the epicentre. In Alva, 31 km away, the estimate is intensity II (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: Helena 30 km, intensity II · Alva 31 km, intensity II · Fairview 31 km, intensity II · Cherokee 33 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 170 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 89,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 63,000× the energy of this one
  3. Around the size people start to feel M 3.0 5.6× the energy of this one
  4. This earthquake M 2.5 about 170 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

The largest earthquake within 50 km since 2016 was M 5.1 on 2016-02-13 — about 7,900 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 36.5311, -98.6044. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Major County, OK 25 km (15 mi) SSE earthquakes near Major County
Woods County, OK 32 km (20 mi) NW earthquakes near Woods County
Alfalfa County, OK 33 km (21 mi) NE earthquakes near Alfalfa County
Woodward County, OK 61 km (38 mi) W earthquakes near Woodward County
Dewey County, OK 72 km (45 mi) SSW earthquakes near Dewey County
Blaine County, OK 74 km (46 mi) SSE earthquakes near Blaine County

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

51 earthquakes have been recorded within 50 km since this one.

  1. 2.4 7 km NNE of Quinlan, Oklahoma
  2. 3.0 7 km NNE of Quinlan, Oklahoma
  3. 2.6 6 km NNW of Ames, Oklahoma
  4. 2.4 8 km NNE of Quinlan, Oklahoma
  5. 2.3 8 km NNE of Quinlan, Oklahoma
  6. 2.4 8 km NNE of Quinlan, Oklahoma
  7. 2.5 8 km NNE of Quinlan, Oklahoma
  8. 2.8 8 km NNE of Quinlan, Oklahoma
  9. 2.5 8 km NNE of Quinlan, Oklahoma
  10. 3.0 16 km SSE of Waynoka, Oklahoma
  11. 2.5 4 km SE of Avard, Oklahoma
  12. 2.4 8 km SSW of Burlington, Oklahoma
  13. 3.2 3 km SSW of Alva, Oklahoma
  14. 2.9 9 km WSW of Waynoka, Oklahoma
  15. 2.8 6 km NNW of Ames, 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

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.