QuakeIndex

Earthquake · reviewed by a seismologist

M 3.5md

36 km W of Saint Croix, U.S. Virgin Islands

Yes. A magnitude 3.5 earthquake was recorded 36 km W of Saint Croix, U.S. Virgin Islands, at 10:38 pm AST on 1 August 2021 (02:38 UTC), 25 km deep.

· 25 km deep · released about 2.5 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Vieques Municipio 52 kmCulebra Municipio 64 kmCeiba Municipio 76 kmNaguabo Municipio 83 kmHumacao Municipio 83 kmFajardo Municipio 85 kmYabucoa Municipio 87 kmMaunabo Municipio 89 kmLuquillo Municipio 92 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 3.5 (md)
Depth
25 km below the surface
Felt
no reports yet
Nearest
Vieques Municipio, 52 km NW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1927 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 57 km (35 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 2.5 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 68,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 3,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 2,100× the energy of this one
  4. This earthquake M 3.5 about 2.5 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 5.2× 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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

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

  1. 6.1 22 km NNE of Saint Croix, U.S. Virgin Islands · 49 km ENE of this epicentre
  2. 5.0 29 km S of Cruz Bay, U.S. Virgin Islands · 47 km NE 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 17.7923, -65.0870. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Vieques Municipio, PR 52 km (32 mi) NW earthquakes near Vieques Municipio
Culebra Municipio, PR 64 km (40 mi) NNW earthquakes near Culebra Municipio
Ceiba Municipio, PR 76 km (47 mi) NW earthquakes near Ceiba Municipio
Naguabo Municipio, PR 83 km (52 mi) NW earthquakes near Naguabo Municipio
Humacao Municipio, PR 83 km (52 mi) WNW earthquakes near Humacao Municipio
Fajardo Municipio, PR 85 km (53 mi) NW earthquakes near Fajardo Municipio

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

Aftershocks so far

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

  1. 2.8 21 km SSW of Saint Croix, U.S. Virgin Islands
  2. 2.8 29 km S of Esperanza, Puerto Rico
  3. 2.8 8 km S of Esperanza, Puerto Rico
  4. 3.1 16 km SSE of Esperanza, Puerto Rico
  5. 2.5 9 km S of Esperanza, Puerto Rico
  6. 3.1 28 km S of Cruz Bay, U.S. Virgin Islands
  7. 2.8 Puerto Rico region
  8. 3.0 18 km S of Esperanza, Puerto Rico
  9. 2.5 Puerto Rico region
  10. 2.7 16 km SSE of Esperanza, Puerto Rico
  11. 2.7 19 km SE of Esperanza, Puerto Rico
  12. 2.3 Puerto Rico region
  13. 2.5 29 km SSW of Charlotte Amalie, U.S. Virgin Islands
  14. 3.3 15 km S of Esperanza, Puerto Rico
  15. 2.5 12 km SE of Esperanza, 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.