QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9md

Puerto Rico region

Yes. A magnitude 3.9 earthquake was recorded in the Puerto Rico region, 87 km (54 mi) NNE of San Juan, PR, at 3:14 am AST on 23 May 2023 (07:14 UTC), 136 km deep.

87 km (54 mi) NNE of San Juan, PR

· 136 km deep · released about 12 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Loíza Municipio 78 kmFajardo Municipio 82 kmRío Grande Municipio 83 kmLuquillo Municipio 83 kmCarolina Municipio 84 kmSan Juan Municipio 86 kmCataño Municipio 87 kmToa Baja Municipio 89 kmCanóvanas Municipio 89 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
Magnitude
M 3.9 (md)
Depth
136 km below the surface
Felt
no reports yet
Nearest
Loíza Municipio, 78 km SSW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1268 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 it was probably too small to be felt, even directly above it. 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 in our catalogue was M 4.4 on 2019-12-28 — about 5.1 times the energy of this one.

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 19.1140, -65.7136. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Loíza Municipio, PR 78 km (49 mi) SSW earthquakes near Loíza Municipio
Fajardo Municipio, PR 82 km (51 mi) S earthquakes near Fajardo Municipio
Río Grande Municipio, PR 83 km (51 mi) S earthquakes near Río Grande Municipio
Luquillo Municipio, PR 83 km (52 mi) S earthquakes near Luquillo Municipio
Carolina Municipio, PR 84 km (52 mi) SSW earthquakes near Carolina Municipio
San Juan Municipio, PR 86 km (53 mi) SSW earthquakes near San Juan Municipio

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

Aftershocks so far

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

  1. 3.0 57 km NNE of San Juan, Puerto Rico
  2. 3.4 60 km NNE of Luquillo, Puerto Rico
  3. 3.4 113 km NNE of Vieques, Puerto Rico
  4. 3.6 69 km N of Suárez, Puerto Rico
  5. 3.6 Puerto Rico region
  6. 4.2 123 km N of Suárez, Puerto Rico
  7. 4.0 123 km NNE of Vieques, Puerto Rico
  8. 3.4 93 km N of San Juan, Puerto Rico
  9. 3.6 74 km N of Culebra, Puerto Rico
  10. 3.3 75 km NNE of Luquillo, Puerto Rico
  11. 3.8 118 km NNE of Vieques, Puerto Rico
  12. 3.6 43 km N of Suárez, Puerto Rico
  13. 3.3 53 km NNE of Vieques, Puerto Rico
  14. 3.6 Puerto Rico region
  15. 3.3 100 km NNE of Vieques, 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.