QuakeIndex

Earthquake · reviewed by a seismologist

M 3.5md

54 km NNE of Luquillo, Puerto Rico

Yes. A magnitude 3.5 earthquake was recorded 54 km NNE of Luquillo, Puerto Rico, 77 km (48 mi) NE of San Juan, PR, at 2:01 am AST on 24 December 2021 (06:01 UTC), 16 km deep.

77 km (48 mi) NE of San Juan, PR

· 16 km deep · released about 2.5 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Fajardo Municipio 48 kmLuquillo Municipio 55 kmCulebra Municipio 55 kmRío Grande Municipio 59 kmCeiba Municipio 63 kmLoíza Municipio 65 kmCanóvanas Municipio 69 kmCarolina Municipio 70 kmNaguabo Municipio 72 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
16 km below the surface
Felt
no reports yet
Nearest
Fajardo Municipio, 48 km SSW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1784 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 60 km (37 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

The largest earthquake within 50 km since 2016 was M 4.8 on 2021-03-09 — about 95 times the energy of this one.

Before 2016, the USGS record lists one earthquake of M5 or more within 50 km:

  1. 5.0 73 km NNE of Vieques, Puerto Rico · 23 km N 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 18.8020, -65.4596. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Fajardo Municipio, PR 48 km (30 mi) SSW earthquakes near Fajardo Municipio
Luquillo Municipio, PR 55 km (34 mi) SSW earthquakes near Luquillo Municipio
Culebra Municipio, PR 55 km (34 mi) SSE earthquakes near Culebra Municipio
Río Grande Municipio, PR 59 km (37 mi) SW earthquakes near Río Grande Municipio
Ceiba Municipio, PR 63 km (39 mi) SSW earthquakes near Ceiba Municipio
Loíza Municipio, PR 65 km (40 mi) SW earthquakes near Loíza Municipio

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

Aftershocks so far

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

  1. 3.1 74 km NNW of Charlotte Amalie, U.S. Virgin Islands
  2. 3.4 77 km NNW of Charlotte Amalie, U.S. Virgin Islands
  3. 3.3 76 km N of Culebra, Puerto Rico
  4. 3.5 28 km NNE of Culebra, Puerto Rico
  5. 2.9 41 km NNE of Suárez, Puerto Rico
  6. 3.3 67 km NNE of Luquillo, Puerto Rico
  7. 3.9 Puerto Rico region
  8. 3.5 32 km NNW of Charlotte Amalie, U.S. Virgin Islands
  9. 3.1 Puerto Rico region
  10. 3.5 34 km N of Culebra, Puerto Rico
  11. 3.2 66 km NNW of Charlotte Amalie, U.S. Virgin Islands
  12. 3.8 62 km N of Culebra, Puerto Rico
  13. 4.0 69 km NNW of Charlotte Amalie, U.S. Virgin Islands
  14. 3.2 62 km NNW of Charlotte Amalie, U.S. Virgin Islands
  15. 3.9 74 km N of Culebra, 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.