QuakeIndex

Earthquake · reviewed by a seismologist

M 3.1md

61 km NNE of Arecibo, Puerto Rico

Yes. A magnitude 3.1 earthquake was recorded 61 km NNE of Arecibo, Puerto Rico, 87 km (54 mi) NW of San Juan, PR, at 8:34 am AST on 23 March 2021 (12:34 UTC), 36 km deep. 1 person has reported feeling it to USGS.

87 km (54 mi) NW of San Juan, PR

· 36 km deep · released about 1,300 lb of TNT

10 km30 km60 km120 km N Barceloneta Municipio 60 kmManatí Municipio 64 kmVega Baja Municipio 65 kmArecibo Municipio 65 kmHatillo Municipio 68 kmDorado Municipio 68 kmVega Alta Municipio 69 kmCamuy Municipio 70 kmQuebradillas Municipio 71 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 3.1 (md)
Depth
36 km below the surface
Felt
1 report · strongest reported intensity II
Nearest
Barceloneta Municipio, 60 km S
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2059 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 19 km (12 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 1,300 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.1 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 270,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 12,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 8,500× the energy of this one
  4. This earthquake M 3.1 about 1,300 lb of TNT
  5. Around the size people start to feel M 3.0 this one released 1.3× 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 2017-08-18 — about 380 times the energy of this one.

Before 2016, the USGS record lists 11 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.4 61 km N of Hatillo, Puerto Rico · 25 km W of this epicentre
  2. 6.0 81 km N of Isabela, Puerto Rico · 44 km WNW of this epicentre
  3. 5.9 78 km N of Arecibo, Puerto Rico · 20 km NNW of this epicentre
  4. 5.8 12 km N of Garrochales, Puerto Rico · 50 km S of this epicentre
  5. 5.7 78 km N of Tierras Nuevas Poniente, Puerto Rico · 17 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 19.0116, -66.5776. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Barceloneta Municipio, PR 60 km (37 mi) S earthquakes near Barceloneta Municipio
Manatí Municipio, PR 64 km (40 mi) S earthquakes near Manatí Municipio
Vega Baja Municipio, PR 65 km (40 mi) SSE earthquakes near Vega Baja Municipio
Arecibo Municipio, PR 65 km (40 mi) S earthquakes near Arecibo Municipio
Hatillo Municipio, PR 68 km (42 mi) SSW earthquakes near Hatillo Municipio
Dorado Municipio, PR 68 km (42 mi) SSE earthquakes near Dorado Municipio

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

Aftershocks so far

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

  1. 3.4 80 km N of Tierras Nuevas Poniente, Puerto Rico
  2. 3.5 72 km N of Tierras Nuevas Poniente, Puerto Rico
  3. 3.5 74 km N of Tierras Nuevas Poniente, Puerto Rico
  4. 3.0 35 km N of Tierras Nuevas Poniente, Puerto Rico
  5. 3.0 Puerto Rico region
  6. 3.2 67 km N of Tierras Nuevas Poniente, Puerto Rico
  7. 2.8 12 km N of Arecibo, Puerto Rico
  8. 3.4 61 km N of Arecibo, Puerto Rico
  9. 3.1 68 km N of Arecibo, Puerto Rico
  10. 3.5 72 km N of Hatillo, Puerto Rico
  11. 3.3 69 km N of Brenas, Puerto Rico
  12. 3.1 51 km N of Hatillo, Puerto Rico
  13. 3.5 22 km NNE of Tierras Nuevas Poniente, Puerto Rico
  14. 3.5 77 km N of Tierras Nuevas Poniente, Puerto Rico
  15. 3.2 46 km N of Hatillo, 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.