QuakeIndex

Earthquake · reviewed by a seismologist

M 3.5md

81 km NNE of Luquillo, Puerto Rico

Yes. A magnitude 3.5 earthquake was recorded 81 km NNE of Luquillo, Puerto Rico, at 9:59 pm AST on 31 January 2021 (01:59 UTC), 25 km deep.

· 25 km deep · released about 3.1 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Fajardo Municipio 76 kmCulebra Municipio 80 kmLuquillo Municipio 82 kmRío Grande Municipio 86 kmLoíza Municipio 88 kmCeiba Municipio 91 kmCarolina Municipio 94 kmCanóvanas Municipio 95 kmSan Juan Municipio 99 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
Fajardo Municipio, 76 km SSW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2035 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 61 km (38 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 3.1 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 55,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 2,500× the energy of this one
  3. Magna, Utah 2020 M 5.7 1,700× the energy of this one
  4. This earthquake M 3.5 about 3.1 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 6.5× 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 4.7 on 2020-11-26 — about 57 times the energy of this one.

Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:

  1. 5.1 122 km NNE of Vieques, Puerto Rico · 42 km NNE of this epicentre
  2. 5.1 92 km N of Suárez, Puerto Rico · 42 km NW of this epicentre
  3. 5.0 73 km NNE of Vieques, Puerto Rico · 12 km WSW 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 19.0436, -65.3910. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Fajardo Municipio, PR 76 km (47 mi) SSW earthquakes near Fajardo Municipio
Culebra Municipio, PR 80 km (50 mi) S earthquakes near Culebra Municipio
Luquillo Municipio, PR 82 km (51 mi) SSW earthquakes near Luquillo Municipio
Río Grande Municipio, PR 86 km (53 mi) SSW earthquakes near Río Grande Municipio
Loíza Municipio, PR 88 km (55 mi) SW earthquakes near Loíza Municipio
Ceiba Municipio, PR 91 km (57 mi) SSW earthquakes near Ceiba Municipio

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

Aftershocks so far

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

  1. 3.9 86 km N of Culebra, Puerto Rico
  2. 2.5 87 km NNE of Vieques, Puerto Rico
  3. 3.4 84 km NNE of Luquillo, Puerto Rico
  4. 3.3 86 km N of Culebra, Puerto Rico
  5. 3.1 Puerto Rico region
  6. 3.7 89 km N of Culebra, Puerto Rico
  7. 3.3 77 km NNE of Luquillo, Puerto Rico
  8. 3.5 36 km NNE of Culebra, Puerto Rico
  9. 3.7 102 km N of Charlotte Amalie, U.S. Virgin Islands
  10. 3.6 Puerto Rico region
  11. 3.7 69 km N of Culebra, Puerto Rico
  12. 3.4 71 km N of Culebra, Puerto Rico
  13. 3.7 74 km NNW of Charlotte Amalie, U.S. Virgin Islands
  14. 3.6 Virgin Islands
  15. 2.6 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.