QuakeIndex

Earthquake · reviewed by a seismologist

M 3.1md

84 km N of San Antonio, Puerto Rico

Yes. A magnitude 3.1 earthquake was recorded 84 km N of San Antonio, Puerto Rico, at 8:35 pm AST on 12 October 2018 (00:35 UTC), 72 km deep.

· 72 km deep · released about 1,200 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Aguadilla Municipio 85 kmIsabela Municipio 88 kmQuebradillas Municipio 92 kmAguada Municipio 96 kmCamuy Municipio 97 kmMoca Municipio 98 kmRincón Municipio 100 kmHatillo Municipio 101 kmSan Sebastián Municipio 105 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
72 km below the surface
Felt
no reports yet
Nearest
Aguadilla Municipio, 85 km S
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2952 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. 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 1,200 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 4.2 on 2017-08-27 — about 46 times the energy of this one.

Before 2016, the USGS record lists 13 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.7 45 km N of San Antonio, Puerto Rico · 40 km SSE of this epicentre
  2. 6.0 93 km NNW of San Antonio, Puerto Rico · 9 km NNW of this epicentre
  3. 6.0 81 km N of Isabela, Puerto Rico · 34 km E of this epicentre
  4. 6.0 67 km NNW of San Antonio, Puerto Rico · 18 km S of this epicentre
  5. 5.7 88 km N of San Antonio, Puerto Rico · 4 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 19.2401, -67.2501. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Aguadilla Municipio, PR 85 km (53 mi) S earthquakes near Aguadilla Municipio
Isabela Municipio, PR 88 km (54 mi) SSE earthquakes near Isabela Municipio
Quebradillas Municipio, PR 92 km (57 mi) SSE earthquakes near Quebradillas Municipio
Aguada Municipio, PR 96 km (60 mi) S earthquakes near Aguada Municipio
Camuy Municipio, PR 97 km (60 mi) SSE earthquakes near Camuy Municipio
Moca Municipio, PR 98 km (61 mi) S earthquakes near Moca Municipio

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

Aftershocks so far

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

  1. 2.7 43 km N of San Antonio, Puerto Rico
  2. 2.8 70 km NNW of San Antonio, Puerto Rico
  3. 3.0 74 km N of San Antonio, Puerto Rico
  4. 3.1 59 km N of Hatillo, Puerto Rico
  5. 3.1 81 km NW of San Antonio, Puerto Rico
  6. 3.1 61 km N of Isabela, Puerto Rico
  7. 2.9 63 km N of Isabela, Puerto Rico
  8. 2.5 46 km NNW of San Antonio, Puerto Rico
  9. 2.9 81 km NNW of San Antonio, Puerto Rico
  10. 2.8 47 km NW of San Antonio, Puerto Rico
  11. 2.5 47 km N of Isabela, Puerto Rico
  12. 2.3 53 km NW of San Antonio, Puerto Rico
  13. 2.8 43 km NNW of San Antonio, Puerto Rico
  14. 3.0 84 km NNW of San Antonio, Puerto Rico
  15. 2.7 54 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.