QuakeIndex

Earthquake · reviewed by a seismologist

M 2.5md

Earthquake near Arroyo, PR

No earthquake was likely felt in Arroyo in the 24 hours to 8:31 pm AST (00:31 UTC). The last one was M 3.3, 39 km (24 mi) WSW, at 8:40 am AST on 1 November 2026, estimated intensity II (weak) in town. Every earthquake near Arroyo

This page: a magnitude 2.5 earthquake was recorded 9 km (6 mi) south-southwest of Arroyo, PR, at 11:13 pm AST on 7 December 2018 (03:13 UTC), 9.0 km deep.

USGS: 9 km SSW of Arroyo, Puerto Rico

58 km (36 mi) S of San Juan, PR · 39 km (24 mi) S of Caguas, PR

11:13 pm AST, Dec 7, 2018 · · 9.0 km deep · released about 190 lb of TNT

Every earthquake near Arroyo Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Arroyo Municipio 11 kmGuayama Municipio 11 kmPatillas Municipio 17 kmSalinas Municipio 21 kmMaunabo Municipio 24 kmCayey Municipio 25 kmYabucoa Municipio 31 kmSan Lorenzo Municipio 31 kmSanta Isabel 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
11:13 pm AST on 7 December 2018 ()
Where
9 km (6 mi) south-southwest of Arroyo, PR · earthquakes near Arroyo
Magnitude
M 2.5 (md)
Depth
9.0 km below the surface
Felt
no reports yet
Nearest
Arroyo Municipio, 11 km NNE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2896 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 21 km (13 mi) from the epicentre. In Arroyo, 9 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.

Likely felt in: Guayama 11 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 190 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 80,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 57,000× the energy of this one
  3. Around the size people start to feel M 3.0 5.1× the energy of this one
  4. This earthquake M 2.5 about 190 lb of TNT

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 4.6 on 2016-12-05 — about 1,300 times the energy of this one.

Before 2016, the USGS record lists one earthquake of M5 or more within 50 km:

  1. 5.1 3 km W of Aguas Buenas, Puerto Rico · 42 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 17.8850, -66.0856. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Arroyo Municipio, PR 11 km (7 mi) NNE earthquakes near Arroyo Municipio
Guayama Municipio, PR 11 km (7 mi) NNW earthquakes near Guayama Municipio
Patillas Municipio, PR 17 km (10 mi) NE earthquakes near Patillas Municipio
Salinas Municipio, PR 21 km (13 mi) WNW earthquakes near Salinas Municipio
Maunabo Municipio, PR 24 km (15 mi) ENE earthquakes near Maunabo Municipio
Cayey Municipio, PR 25 km (16 mi) NNW earthquakes near Cayey Municipio

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

Aftershocks so far

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

  1. 2.1 9 km SSE of Arroyo, Puerto Rico
  2. 2.3 9 km SSE of Arroyo, Puerto Rico
  3. 2.1 5 km SSE of Arroyo, Puerto Rico
  4. 1.9 4 km N of Palmarejo, Puerto Rico
  5. 1.9 1 km ENE of El Ojo, Puerto Rico
  6. 2.1 22 km SSE of Lamboglia, Puerto Rico
  7. 2.0 0 km SSE of Playita Cortada, Puerto Rico
  8. 1.6 5 km SE of Arroyo, Puerto Rico
  9. 2.3 4 km NW of Palomas, Puerto Rico
  10. 1.8 11 km S of Emajagua, Puerto Rico
  11. 2.5 1 km ESE of Salinas, Puerto Rico
  12. 1.9 2 km WNW of Las Ollas, Puerto Rico
  13. 2.1 23 km S of Emajagua, Puerto Rico
  14. 1.8 9 km SSW of Emajagua, Puerto Rico
  15. 2.2 24 km SE of Emajagua, 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.