QuakeIndex

Earthquake · reviewed by a seismologist

M 2.9md

Earthquake near San Juan, PR

No earthquake was likely felt in San Juan in the 24 hours to 4:35 pm AST (20:35 UTC). The last one was M 4.1, 99 km (62 mi) SE, at 5:44 am AST on 28 October 2026, estimated intensity II (weak) in town; 5 felt reports to USGS. Every earthquake near San Juan

This page: a magnitude 2.9 earthquake was recorded 37 km (23 mi) north of San Juan, PR, at 8:11 pm AST on 4 December 2018 (00:11 UTC), 50 km deep.

USGS: 37 km N of San Juan, Puerto Rico

45 km (28 mi) NNW of San Juan, PR

8:11 pm AST, Dec 4, 2018 · · 50 km deep · released about 630 lb of TNT

Every earthquake near San Juan Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Dorado Municipio 37 kmToa Baja Municipio 38 kmCataño Municipio 39 kmSan Juan Municipio 43 kmVega Alta Municipio 44 kmVega Baja Municipio 45 kmLoíza Municipio 46 kmToa Alta Municipio 49 kmCarolina Municipio 49 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
8:11 pm AST on 4 December 2018 ()
Where
37 km (23 mi) north of San Juan, PR · earthquakes near San Juan
Magnitude
M 2.9 (md)
Depth
50 km below the surface
Felt
no reports yet
Nearest
Dorado Municipio, 37 km SSW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2899 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 San Juan, 37 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 630 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.9 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 24,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 17,000× the energy of this one
  3. Around the size people start to feel M 3.0 1.5× the energy of this one
  4. This earthquake M 2.9 about 630 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 4.8 on 2017-08-18 — about 760 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

  1. 5.8 12 km N of Garrochales, Puerto Rico · 50 km WSW of this epicentre
  2. 5.5 64 km N of Tierras Nuevas Poniente, Puerto Rico · 43 km NW of this epicentre
  3. 5.1 66 km N of Brenas, Puerto Rico · 37 km NW of this epicentre
  4. 5.0 3 km N of Brenas, Puerto Rico · 38 km SSW 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 18.7968, -66.1650. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Dorado Municipio, PR 37 km (23 mi) SSW earthquakes near Dorado Municipio
Toa Baja Municipio, PR 38 km (24 mi) S earthquakes near Toa Baja Municipio
Cataño Municipio, PR 39 km (24 mi) S earthquakes near Cataño Municipio
San Juan Municipio, PR 43 km (27 mi) SSE earthquakes near San Juan Municipio
Vega Alta Municipio, PR 44 km (27 mi) SSW earthquakes near Vega Alta Municipio
Vega Baja Municipio, PR 45 km (28 mi) SSW earthquakes near Vega Baja Municipio

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

Aftershocks so far

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

  1. 2.6 68 km N of Suárez, Puerto Rico
  2. 2.4 24 km N of Dorado, Puerto Rico
  3. 2.0 18 km N of Garrochales, Puerto Rico
  4. 2.0 20 km NE of San Juan, Puerto Rico
  5. 3.1 37 km NNE of Vieques, Puerto Rico
  6. 2.5 6 km ESE of San Juan, Puerto Rico
  7. 2.1 0 km SW of Toa Alta, Puerto Rico
  8. 2.6 24 km N of San Juan, Puerto Rico
  9. 2.9 13 km NNW of Brenas, Puerto Rico
  10. 2.1 37 km N of San Juan, Puerto Rico
  11. 1.5 18 km NNE of Tierras Nuevas Poniente, Puerto Rico
  12. 2.5 12 km N of Brenas, Puerto Rico
  13. 2.6 32 km N of Garrochales, Puerto Rico
  14. 3.0 2 km ENE of Guaynabo, Puerto Rico
  15. 2.8 71 km N of San Juan, 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.