QuakeIndex

Earthquake · reviewed by a seismologist

M 2.8md

Earthquake near Cayey, PR

No earthquake was likely felt in Cayey in the 24 hours to 6:02 pm AST (22:02 UTC). The last one was M 3.3, 38 km (24 mi) SW, at 8:40 am AST on 1 November 2026, estimated intensity II (weak) in town. Every earthquake near Cayey

This page: a magnitude 2.8 earthquake was recorded in Cayey, PR, at 7:30 pm AST on 11 December 2021 (23:30 UTC), 18 km deep.

USGS: 1 km SSW of Cayey, Puerto Rico

36 km (22 mi) SSW of San Juan, PR · 20 km (13 mi) SW of Caguas, PR

7:30 pm AST, Dec 11, 2021 · · 18 km deep · released about 550 lb of TNT

Every earthquake near Cayey Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Cayey Municipio 2 kmCidra Municipio 8 kmAibonito Municipio 10 kmComerío Municipio 15 kmGuayama Municipio 15 kmSalinas Municipio 17 kmCaguas Municipio 18 kmAguas Buenas Municipio 18 kmBarranquitas Municipio 18 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
7:30 pm AST on 11 December 2021 ()
Where
in Cayey, PR · earthquakes near Cayey
Magnitude
M 2.8 (md)
Depth
18 km below the surface
Felt
no reports yet
Nearest
Cayey Municipio, 2 km E
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1796 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 23 km (14 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.

Likely felt in: Cayey in town, intensity II · Sumidero 14 km, intensity II · Guayama 14 km, intensity II · Coamo 20 km, intensity II · Caguas 20 km, intensity II · Jagual 20 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 550 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 28,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 19,000× the energy of this one
  3. Around the size people start to feel M 3.0 1.7× the energy of this one
  4. This earthquake M 2.8 about 550 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 440 times the energy of this one.

Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:

  1. 5.1 3 km W of Aguas Buenas, Puerto Rico · 18 km NNE of this epicentre
  2. 5.0 3 km N of Brenas, Puerto Rico · 48 km NNW 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 18.1013, -66.1728. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Cayey Municipio, PR 2 km (1 mi) E earthquakes near Cayey Municipio
Cidra Municipio, PR 8 km (5 mi) N earthquakes near Cidra Municipio
Aibonito Municipio, PR 10 km (6 mi) WNW earthquakes near Aibonito Municipio
Comerío Municipio, PR 15 km (9 mi) NNW earthquakes near Comerío Municipio
Guayama Municipio, PR 15 km (9 mi) SSE earthquakes near Guayama Municipio
Salinas Municipio, PR 17 km (11 mi) SSW earthquakes near Salinas Municipio

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

Aftershocks so far

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

  1. 2.4 1 km SSE of Salinas, Puerto Rico
  2. 3.0 0 km W of Sumidero, Puerto Rico
  3. 2.4 3 km SSE of Pájaros, Puerto Rico
  4. 3.3 1 km ESE of Guaynabo, Puerto Rico
  5. 3.3 1 km WNW of Morovis, Puerto Rico
  6. 2.1 4 km WNW of Coamo, 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. 2.0 14 km SSE of Ponce, Puerto Rico
  12. 2.2 2 km SSW of Río Cañas Abajo, Puerto Rico
  13. 1.6 5 km S of Ponce, Puerto Rico
  14. 2.0 1 km NW of Ponce, Puerto Rico
  15. 2.5 4 km SSE of Salinas, 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.