QuakeIndex

Earthquake · reviewed by a seismologist

M 3.6md

Earthquake near Pájaros, PR

No earthquake was likely felt in Pájaros in the 24 hours to 9:56 pm AST (01:56 UTC). The last one was M 4.8, 91 km (56 mi) WSW, at 9:19 am AST on 18 September 2026, estimated intensity III (weak) in town; 86 felt reports to USGS. Every earthquake near Pájaros

This page: a magnitude 3.6 earthquake was recorded 2 km (1 mi) east-southeast of Pájaros, PR, at 12:41 am AST on 18 December 2021 (04:41 UTC), 121 km deep. 2 people have reported feeling it to USGS.

USGS: 2 km ESE of Pájaros, Puerto Rico

in Bayamón, PR

12:41 am AST, Dec 18, 2021 · · 121 km deep · released about 4.5 tons of TNT

Every earthquake near Pájaros Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Bayamón Municipio 3 kmToa Alta Municipio 5 kmGuaynabo Municipio 9 kmNaranjito Municipio 9 kmCataño Municipio 11 kmToa Baja Municipio 11 kmAguas Buenas Municipio 14 kmDorado Municipio 15 kmCorozal Municipio 15 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
12:41 am AST on 18 December 2021 ()
Where
2 km (1 mi) east-southeast of Pájaros, PR · earthquakes near Pájaros
Magnitude
M 3.6 (md)
Depth
121 km below the surface
Felt
2 reports · strongest reported intensity II
Measured shaking
intensity II (ShakeMap)
Nearest
Bayamón Municipio, 3 km ESE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1558 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 Pájaros, 2 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: Mucarabones, Candelaria, Toa Alta, Galateo, Bayamón, Candelaria Arenas.

How big was it?

This earthquake released about 4.5 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.7 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 38,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 1,700× the energy of this one
  3. Magna, Utah 2020 M 5.7 1,200× the energy of this one
  4. This earthquake M 3.6 about 4.5 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 9.4× 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 4.6 on 2019-03-12 — about 27 times the energy of this one.

Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:

  1. 5.8 12 km N of Garrochales, Puerto Rico · 45 km WNW of this epicentre
  2. 5.1 3 km W of Aguas Buenas, Puerto Rico · 13 km SSE of this epicentre
  3. 5.0 3 km N of Brenas, Puerto Rico · 22 km NW 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 18.3578, -66.1993. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Bayamón Municipio, PR 3 km (2 mi) ESE earthquakes near Bayamón Municipio
Toa Alta Municipio, PR 5 km (3 mi) W earthquakes near Toa Alta Municipio
Guaynabo Municipio, PR 9 km (6 mi) E earthquakes near Guaynabo Municipio
Naranjito Municipio, PR 9 km (6 mi) SW earthquakes near Naranjito Municipio
Cataño Municipio, PR 11 km (7 mi) NNE earthquakes near Cataño Municipio
Toa Baja Municipio, PR 11 km (7 mi) N earthquakes near Toa Baja Municipio

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

Aftershocks so far

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

  1. 2.4 3 km SSE of Pájaros, Puerto Rico
  2. 3.0 4 km N of Animas, Puerto Rico
  3. 3.3 1 km ESE of Guaynabo, Puerto Rico
  4. 3.3 1 km WNW of Morovis, Puerto Rico
  5. 2.1 4 km WNW of Coamo, Puerto Rico
  6. 2.9 13 km N of Brenas, Puerto Rico
  7. 2.7 6 km SSE of Salinas, Puerto Rico
  8. 2.6 6 km SSE of Salinas, Puerto Rico
  9. 2.2 6 km SSE of Salinas, Puerto Rico
  10. 2.3 6 km SSE of Salinas, Puerto Rico
  11. 2.2 2 km SSW of Río Cañas Abajo, Puerto Rico
  12. 2.5 4 km SSE of Salinas, Puerto Rico
  13. 2.3 6 km NW of Palomas, Puerto Rico
  14. 2.2 2 km E of G. L. Garcia, Puerto Rico
  15. 2.6 2 km WNW of Río Cañas Abajo, 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.