QuakeIndex

Earthquake · reviewed by a seismologist

M 3.7md

131 km NNE of San Juan, Puerto Rico

Yes. A magnitude 3.7 earthquake was recorded 131 km NNE of San Juan, Puerto Rico, at 3:30 am AST on 9 December 2023 (07:30 UTC), 66 km deep. 4 people have reported feeling it to USGS.

· 66 km deep · released about 5.4 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N
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 3.7 (md)
Depth
66 km below the surface
Felt
4 reports · strongest reported intensity III
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1005 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 38 km (24 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 5.4 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.7 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 32,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 1,400× the energy of this one
  3. Magna, Utah 2020 M 5.7 1,000× the energy of this one
  4. This earthquake M 3.7 about 5.4 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 11× 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 2023-02-28 — about 13 times the energy of this one.

Before 2016, the USGS record lists one earthquake of M5 or more within 50 km:

  1. 5.1 92 km N of Suárez, Puerto Rico · 42 km SSE 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 19.6215, -65.8188. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 3.6 132 km NNE of Vieques, Puerto Rico
  2. 3.5 136 km NNE of Vieques, Puerto Rico
  3. 3.3 139 km NNE of Vieques, Puerto Rico
  4. 3.8 135 km NNE of Vieques, Puerto Rico
  5. 3.5 131 km NNE of Vieques, Puerto Rico
  6. 3.7 123 km NNE of Vieques, Puerto Rico
  7. 4.0 138 km NNE of Vieques, Puerto Rico
  8. 3.7 139 km NNE of Vieques, Puerto Rico
  9. 3.4 138 km NNE of Vieques, Puerto Rico
  10. 3.8 135 km NNE of Vieques, Puerto Rico
  11. 3.7 138 km NNE of Vieques, Puerto Rico
  12. 3.8 140 km NNE of Vieques, Puerto Rico
  13. 3.4 130 km NNE of Vieques, Puerto Rico
  14. 3.3 119 km N of San Juan, Puerto Rico
  15. 4.0 110 km N of Brenas, Puerto Rico

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.