QuakeIndex

Earthquake · reviewed by a seismologist

M 3.1md

50 km NNW of San Antonio, Puerto Rico

Yes. A magnitude 3.1 earthquake was recorded 50 km NNW of San Antonio, Puerto Rico, at 9:48 pm AST on 8 August 2023 (01:48 UTC), 8.6 km deep.

· 8.6 km deep · released about 1,400 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Aguadilla Municipio 50 kmIsabela Municipio 57 kmAguada Municipio 59 kmRincón Municipio 62 kmMoca Municipio 63 kmQuebradillas Municipio 64 kmAñasco Municipio 70 kmCamuy Municipio 70 kmSan Sebastián Municipio 73 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
8.6 km below the surface
Felt
no reports yet
Nearest
Aguadilla Municipio, 50 km SSE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1191 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 41 km (25 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 1,400 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 6.7 240,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 11,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 7,700× the energy of this one
  4. This earthquake M 3.1 about 1,400 lb of TNT
  5. Around the size people start to feel M 3.0 this one released 1.5× 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 6.0 on 2019-09-24 — about 22,000 times the energy of this one.

Before 2016, the USGS record lists 18 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.7 45 km N of San Antonio, Puerto Rico · 24 km E of this epicentre
  2. 7.1 24 km NNW of San Antonio, Puerto Rico · 26 km SE of this epicentre
  3. 6.8 94 km NE of Punta Cana, Dominican Republic · 48 km NW of this epicentre
  4. 6.4 32 km NW of Aguadilla, Puerto Rico · 31 km S of this epicentre
  5. 6.1 15 km WNW of San Antonio, Puerto Rico · 39 km SSE 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 18.8880, -67.3417. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Aguadilla Municipio, PR 50 km (31 mi) SSE earthquakes near Aguadilla Municipio
Isabela Municipio, PR 57 km (35 mi) SE earthquakes near Isabela Municipio
Aguada Municipio, PR 59 km (37 mi) SSE earthquakes near Aguada Municipio
Rincón Municipio, PR 62 km (38 mi) S earthquakes near Rincón Municipio
Moca Municipio, PR 63 km (39 mi) SSE earthquakes near Moca Municipio
Quebradillas Municipio, PR 64 km (40 mi) SE earthquakes near Quebradillas 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. 3.0 12 km NNE of Isabela, Puerto Rico
  2. 3.5 73 km NW of San Antonio, Puerto Rico
  3. 2.8 31 km NW of Aguadilla, Puerto Rico
  4. 3.5 19 km NNW of San Antonio, Puerto Rico
  5. 3.4 71 km N of Isabela, Puerto Rico
  6. 3.0 21 km NNE of Isabela, Puerto Rico
  7. 3.1 51 km NNW of San Antonio, Puerto Rico
  8. 3.2 49 km N of San Antonio, Puerto Rico
  9. 3.2 Puerto Rico region
  10. 3.9 65 km N of Isabela, Puerto Rico
  11. 2.8 26 km NNE of Isabela, Puerto Rico
  12. 3.5 94 km NNW of San Antonio, Puerto Rico
  13. 3.2 64 km NNW of San Antonio, Puerto Rico
  14. 2.8 Mona Passage
  15. 3.4 71 km NNW 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.