QuakeIndex

Earthquake · reviewed by a seismologist

M 3.1md

Earthquake near Isabela, PR

No earthquake was likely felt in Isabela in the 24 hours to 5:27 pm AST (21:27 UTC). The last one was M 3.4, 31 km (19 mi) N, at 9:00 pm AST on 27 October 2026, estimated intensity II (weak) in town. Every earthquake near Isabela

This page: a magnitude 3.1 earthquake was recorded 12 km (8 mi) northwest of Isabela, PR, at 6:58 pm AST on 12 July 2021 (22:58 UTC), 82 km deep.

USGS: 9 km N of San Antonio, Puerto Rico

41 km (26 mi) WNW of Arecibo, PR · 111 km (69 mi) W of San Juan, PR

6:58 pm AST, Jul 12, 2021 · · 82 km deep · released about 1,200 lb of TNT

Every earthquake near Isabela Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Aguadilla Municipio 12 kmIsabela Municipio 14 kmQuebradillas Municipio 23 kmMoca Municipio 23 kmAguada Municipio 24 kmCamuy Municipio 30 kmRincón Municipio 31 kmSan Sebastián Municipio 31 kmAñasco Municipio 33 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
6:58 pm AST on 12 July 2021 ()
Where
12 km (8 mi) northwest of Isabela, PR · earthquakes near Isabela
Magnitude
M 3.1 (md)
Depth
82 km below the surface
Felt
no reports yet
Nearest
Aguadilla Municipio, 12 km SSW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1948 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 Isabela, 12 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.

Earthquakes near other towns within 30 km: Rafael Hernandez, Mora, Caban, Aceitunas, Aguadilla, Moca.

How big was it?

This earthquake released about 1,200 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 6.7 280,000× 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 8,800× the energy of this one
  4. This earthquake M 3.1 about 1,200 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 2019-11-29 — about 370 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. 7.7 45 km N of San Antonio, Puerto Rico · 36 km N of this epicentre
  2. 7.1 24 km NNW of San Antonio, Puerto Rico · 16 km NW of this epicentre
  3. 6.4 32 km NW of Aguadilla, Puerto Rico · 30 km W of this epicentre
  4. 6.3 6 km WNW of Aguadilla, Puerto Rico · 19 km SW of this epicentre
  5. 6.1 15 km WNW of San Antonio, Puerto Rico · 14 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 18.5818, -67.1040. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Aguadilla Municipio, PR 12 km (7 mi) SSW earthquakes near Aguadilla Municipio
Isabela Municipio, PR 14 km (9 mi) SE earthquakes near Isabela Municipio
Quebradillas Municipio, PR 23 km (14 mi) SE earthquakes near Quebradillas Municipio
Moca Municipio, PR 23 km (14 mi) S earthquakes near Moca Municipio
Aguada Municipio, PR 24 km (15 mi) SSW earthquakes near Aguada Municipio
Camuy Municipio, PR 30 km (18 mi) ESE earthquakes near Camuy Municipio

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

Aftershocks so far

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

  1. 3.0 1 km SW of Mayagüez, Puerto Rico
  2. 3.5 40 km N of Carrizales, Puerto Rico
  3. 3.3 43 km NW of San Antonio, Puerto Rico
  4. 3.2 42 km NW of San Antonio, Puerto Rico
  5. 2.5 6 km SE of Espino, Puerto Rico
  6. 3.4 42 km N of San Antonio, Puerto Rico
  7. 3.3 10 km SW of Stella, Puerto Rico
  8. 3.3 50 km N of Isabela, Puerto Rico
  9. 3.5 Mona Passage
  10. 3.1 Puerto Rico region
  11. 3.2 5 km SW of Stella, Puerto Rico
  12. 2.4 19 km N of Quebradillas, Puerto Rico
  13. 3.1 45 km NW of Aguadilla, Puerto Rico
  14. 3.3 26 km N of Hatillo, Puerto Rico
  15. 3.2 29 km NNW of Rincón, 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.