QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9md

163 km NNE of Cruz Bay, U.S. Virgin Islands

Yes. A magnitude 3.9 earthquake was recorded 163 km NNE of Cruz Bay, U.S. Virgin Islands at 08:09 UTC on 2023-12-18, 45 km deep.

· 45 km deep · released about 12 tons of TNT

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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
Magnitude
M 3.9 (md)
Depth
45 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 988 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 80 km (50 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.

How big was it?

This earthquake released about 12 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 14,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 640× the energy of this one
  3. Magna, Utah 2020 M 5.7 450× the energy of this one
  4. This earthquake M 3.9 about 12 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 25× 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 5.0 on 2019-10-06 — about 35 times the energy of this one.

Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:

  1. 6.2 131 km NNE of Cruz Bay, U.S. Virgin Islands · 32 km SSW of this epicentre
  2. 5.0 127 km NNE of Cruz Bay, U.S. Virgin Islands · 36 km SSW of this epicentre

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 19.7678, -64.4260. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 4.0 150 km NNE of Cruz Bay, U.S. Virgin Islands
  2. 3.7 135 km NNE of Cruz Bay, U.S. Virgin Islands
  3. 4.1 176 km NNE of Cruz Bay, U.S. Virgin Islands
  4. 3.4 148 km NNE of Cruz Bay, U.S. Virgin Islands
  5. 3.9 149 km NNE of Cruz Bay, U.S. Virgin Islands
  6. 3.8 129 km NNE of Cruz Bay, U.S. Virgin Islands
  7. 3.8 151 km NNE of Cruz Bay, U.S. Virgin Islands
  8. 3.1 183 km NNE of Cruz Bay, U.S. Virgin Islands
  9. 3.4 138 km NNE of Cruz Bay, U.S. Virgin Islands
  10. 3.9 128 km N of Cruz Bay, U.S. Virgin Islands
  11. 3.9 165 km NNE of Cruz Bay, U.S. Virgin Islands
  12. 3.7 140 km NNE of Cruz Bay, U.S. Virgin Islands
  13. 3.3 146 km N of Charlotte Amalie, U.S. Virgin Islands
  14. 3.7 123 km NNE of Cruz Bay, U.S. Virgin Islands
  15. 3.8 144 km N of Cruz Bay, U.S. Virgin Islands

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.