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, at 3:31 am AST on 4 June 2023 (07:31 UTC), 102 km deep.

· 102 km deep · released about 10 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
102 km below the surface
Felt
no reports yet
Nearest
Loíza Municipio, 122 km SSW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1257 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 10 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 16,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 730× the energy of this one
  3. Magna, Utah 2020 M 5.7 520× the energy of this one
  4. This earthquake M 3.9 about 10 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 22× 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 2023-02-28 — about 6.7 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 19.5195, -65.7108. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Loíza Municipio, PR 122 km (76 mi) SSW earthquakes near Loíza Municipio
Cataño Municipio, PR 128 km (80 mi) SSW earthquakes near Cataño Municipio
Toa Baja Municipio, PR 129 km (80 mi) SSW earthquakes near Toa Baja Municipio
Dorado Municipio, PR 130 km (81 mi) SSW earthquakes near Dorado Municipio
Vega Baja Municipio, PR 139 km (86 mi) SSW earthquakes near Vega Baja Municipio
Manatí Municipio, PR 145 km (90 mi) SW earthquakes near Manatí Municipio

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.

  1. 3.8 138 km NNE of Suárez, Puerto Rico
  2. 3.7 145 km NNE of Vieques, Puerto Rico
  3. 3.9 141 km N of Suárez, Puerto Rico
  4. 4.2 123 km N of Suárez, Puerto Rico
  5. 3.7 135 km N of Suárez, Puerto Rico
  6. 3.1 132 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. 3.3 104 km N of San Juan, Puerto Rico
  10. 3.5 116 km N of San Juan, Puerto Rico
  11. 3.8 133 km NNE of Vieques, Puerto Rico
  12. 3.7 141 km NNE of Vieques, Puerto Rico
  13. 3.7 142 km NNE of Vieques, Puerto Rico
  14. 3.8 118 km NNE of Vieques, Puerto Rico
  15. 3.5 121 km N of San Juan, 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.