QuakeIndex

Earthquake · reviewed by a seismologist

M 3.6md

97 km N of Charlotte Amalie, U.S. Virgin Islands

Yes. A magnitude 3.6 earthquake was recorded 97 km N of Charlotte Amalie, U.S. Virgin Islands, at 7:11 pm AST on 18 July 2021 (23:11 UTC), 89 km deep. 1 person has reported feeling it to USGS.

· 89 km deep · released about 3.3 tons of TNT

10 km30 km60 km120 km N Culebra Municipio 104 kmFajardo Municipio 110 kmLuquillo Municipio 119 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 3.6 (md)
Depth
89 km below the surface
Felt
1 report · strongest reported intensity III
Nearest
Culebra Municipio, 104 km SSW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1942 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 3.3 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.6 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 51,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 2,300× the energy of this one
  3. Magna, Utah 2020 M 5.7 1,600× the energy of this one
  4. This earthquake M 3.6 about 3.3 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 6.9× 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 2021-02-06 — about 140 times the energy of this one.

Before 2016, the USGS record lists 13 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.1 91 km N of Charlotte Amalie, U.S. Virgin Islands · 21 km ESE of this epicentre
  2. 6.0 112 km N of Charlotte Amalie, U.S. Virgin Islands · 18 km NE of this epicentre
  3. 5.9 68 km N of Cruz Bay, U.S. Virgin Islands · 46 km SE of this epicentre
  4. 5.6 112 km N of Charlotte Amalie, U.S. Virgin Islands · 21 km NE of this epicentre
  5. 5.3 78 km NNE of Cruz Bay, U.S. Virgin Islands · 47 km ESE 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 19.2225, -65.0258. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Culebra Municipio, PR 104 km (65 mi) SSW earthquakes near Culebra Municipio
Fajardo Municipio, PR 110 km (68 mi) SSW earthquakes near Fajardo Municipio
Luquillo Municipio, PR 119 km (74 mi) SW earthquakes near Luquillo Municipio
Río Grande Municipio, PR 124 km (77 mi) SW earthquakes near Río Grande Municipio
Ceiba Municipio, PR 125 km (77 mi) SSW earthquakes near Ceiba Municipio
Loíza Municipio, PR 130 km (80 mi) SW earthquakes near Loíza Municipio

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

Aftershocks so far

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

  1. 3.8 88 km N of Cruz Bay, U.S. Virgin Islands
  2. 3.5 55 km N of Charlotte Amalie, U.S. Virgin Islands
  3. 3.6 63 km N of Charlotte Amalie, U.S. Virgin Islands
  4. 3.6 106 km N of Charlotte Amalie, U.S. Virgin Islands
  5. 3.7 107 km NNW of Charlotte Amalie, U.S. Virgin Islands
  6. 3.7 114 km N of Cruz Bay, U.S. Virgin Islands
  7. 3.6 90 km N of Charlotte Amalie, U.S. Virgin Islands
  8. 3.7 76 km N of Cruz Bay, U.S. Virgin Islands
  9. 4.0 109 km N of Cruz Bay, U.S. Virgin Islands
  10. 3.6 98 km NNW of Charlotte Amalie, U.S. Virgin Islands
  11. 3.6 89 km N of Culebra, Puerto Rico
  12. 3.3 69 km NNW of Charlotte Amalie, U.S. Virgin Islands
  13. 3.9 75 km N of Charlotte Amalie, U.S. Virgin Islands
  14. 3.4 Puerto Rico region
  15. 3.7 107 km N of Charlotte Amalie, 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.