QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9md

Earthquake near Aguadilla, PR

No earthquake was likely felt in Aguadilla in the 24 hours to 5:19 pm AST (21:19 UTC). The last one was M 3.5, 4 km (3 mi) SE, at 12:03 am AST on 6 November 2026, estimated intensity II (weak) in town. Every earthquake near Aguadilla

This page: a magnitude 3.9 earthquake was recorded 47 km (29 mi) west of Aguadilla, PR, at 2:04 pm AST on 21 January 2021 (18:04 UTC), 104 km deep. 3 people have reported feeling it to USGS.

USGS: 40 km WNW of Rincón, Puerto Rico

58 km (36 mi) NW of Mayagüez, PR · 116 km (72 mi) WNW of Ponce, PR

2:04 pm AST, Jan 21, 2021 · · 104 km deep · released about 11 tons of TNT

Every earthquake near Aguadilla Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Rincón Municipio 40 kmAguada Municipio 45 kmAguadilla Municipio 47 kmAñasco Municipio 54 kmMayagüez Municipio 55 kmMoca Municipio 56 kmIsabela Municipio 61 kmHormigueros Municipio 64 kmSan Sebastián Municipio 68 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
2:04 pm AST on 21 January 2021 ()
Where
47 km (29 mi) west of Aguadilla, PR · earthquakes near Aguadilla
Magnitude
M 3.9 (md)
Depth
104 km below the surface
Felt
3 reports · strongest reported intensity IV
Nearest
Rincón Municipio, 40 km ESE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2055 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. In Aguadilla, 47 km away, the estimate is intensity II (weak). 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 11 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 15,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 660× the energy of this one
  3. Magna, Utah 2020 M 5.7 470× the energy of this one
  4. This earthquake M 3.9 about 11 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 24× 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 4.4 on 2017-10-01 — about 5.2 times the energy of this one.

Before 2016, the USGS record lists 9 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.1 24 km NNW of San Antonio, Puerto Rico · 48 km ENE of this epicentre
  2. 6.4 32 km NW of Aguadilla, Puerto Rico · 26 km ENE of this epicentre
  3. 6.3 6 km WNW of Aguadilla, Puerto Rico · 40 km E of this epicentre
  4. 6.3 58 km E of Punta Cana, Dominican Republic · 28 km W of this epicentre
  5. 6.1 15 km WNW of San Antonio, Puerto Rico · 38 km E 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 18.4976, -67.5925. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Rincón Municipio, PR 40 km (25 mi) ESE earthquakes near Rincón Municipio
Aguada Municipio, PR 45 km (28 mi) ESE earthquakes near Aguada Municipio
Aguadilla Municipio, PR 47 km (29 mi) E earthquakes near Aguadilla Municipio
Añasco Municipio, PR 54 km (34 mi) ESE earthquakes near Añasco Municipio
Mayagüez Municipio, PR 55 km (34 mi) SW earthquakes near Mayagüez Municipio
Moca Municipio, PR 56 km (35 mi) ESE earthquakes near Moca Municipio

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

Aftershocks so far

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

  1. 3.2 Mona Passage
  2. 3.0 18 km WNW of Rincón, Puerto Rico
  3. 3.4 53 km NW of San Antonio, Puerto Rico
  4. 3.4 27 km NW of Rincón, Puerto Rico
  5. 3.4 68 km NW of San Antonio, Puerto Rico
  6. 3.1 60 km NW of San Antonio, Puerto Rico
  7. 3.2 44 km NW of San Antonio, Puerto Rico
  8. 3.3 47 km ESE of Punta Cana, Dominican Republic
  9. 3.1 72 km NW of Aguadilla, Puerto Rico
  10. 2.8 34 km WNW of Rincón, Puerto Rico
  11. 3.4 71 km NW of Rincón, Puerto Rico
  12. 2.0 2 km NNE of Rincón, Puerto Rico
  13. 3.2 59 km W of Stella, Puerto Rico
  14. 3.6 50 km NW of Rincón, Puerto Rico
  15. 3.2 69 km NW of San Antonio, 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.