QuakeIndex

Earthquake · reviewed by a seismologist

M 3.1md

Earthquake near Central Aguirre, PR

No earthquake was likely felt in Central Aguirre in the 24 hours to 11:08 pm AST (03:08 UTC). The last one was M 3.0, 23 km (14 mi) WSW, at 7:09 pm AST on 5 November 2026, estimated intensity II (weak) in town. Every earthquake near Central Aguirre

This page: a magnitude 3.1 earthquake was recorded in Central Aguirre, PR, at 6:31 pm AST on 9 September 2021 (22:31 UTC), 12 km deep. 3 people have reported feeling it to USGS.

USGS: 0 km NNE of Central Aguirre, Puerto Rico

53 km (33 mi) SSW of San Juan, PR · 36 km (23 mi) SSW of Caguas, PR

6:31 pm AST, Sep 9, 2021 · · 12 km deep · released about 1,400 lb of TNT

Every earthquake near Central Aguirre Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Salinas Municipio 5 kmGuayama Municipio 9 kmSanta Isabel Municipio 18 kmCayey Municipio 18 kmArroyo Municipio 19 kmAibonito Municipio 20 kmCoamo Municipio 22 kmCidra Municipio 25 kmPatillas Municipio 25 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
6:31 pm AST on 9 September 2021 ()
Where
in Central Aguirre, PR · earthquakes near Central Aguirre
Magnitude
M 3.1 (md)
Depth
12 km below the surface
Felt
3 reports · strongest reported intensity III
Nearest
Salinas Municipio, 5 km WNW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1557 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 41 km (25 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: Guayama 12 km, intensity III · Cayey 18 km, intensity II · Santa Isabel 19 km, intensity II · Coamo 20 km, intensity II · Río Cañas Abajo 28 km, intensity II · Sumidero 31 km, intensity II · Jagual 33 km, intensity II · Caguas 36 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 1,400 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 6.7 230,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 10,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 7,400× the energy of this one
  4. This earthquake M 3.1 about 1,400 lb of TNT
  5. Around the size people start to feel M 3.0 this one released 1.5× 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 5.0 on 2020-01-07 — about 660 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 · 35 km NNE 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 17.9563, -66.2218. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Salinas Municipio, PR 5 km (3 mi) WNW earthquakes near Salinas Municipio
Guayama Municipio, PR 9 km (6 mi) ENE earthquakes near Guayama Municipio
Santa Isabel Municipio, PR 18 km (11 mi) W earthquakes near Santa Isabel Municipio
Cayey Municipio, PR 18 km (11 mi) NNE earthquakes near Cayey Municipio
Arroyo Municipio, PR 19 km (12 mi) E earthquakes near Arroyo Municipio
Aibonito Municipio, PR 20 km (12 mi) NNW earthquakes near Aibonito 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. 2.0 5 km S of Morovis, Puerto Rico
  2. 2.7 0 km NW of Aguas Buenas, Puerto Rico
  3. 2.5 1 km SE of Salinas, Puerto Rico
  4. 2.3 16 km SSE of Ponce, Puerto Rico
  5. 2.7 2 km W of Pastos, Puerto Rico
  6. 3.3 4 km SSW of Las Piedras, Puerto Rico
  7. 2.4 2 km NNW of Potala Pastillo, Puerto Rico
  8. 2.9 0 km WNW of Aguas Buenas, Puerto Rico
  9. 2.1 1 km SSE of Las Ochenta, Puerto Rico
  10. 3.2 1 km ESE of Emajagua, Puerto Rico
  11. 2.3 6 km SSW of Potala Pastillo, Puerto Rico
  12. 2.9 7 km S of Ponce, Puerto Rico
  13. 2.9 8 km SSE of Tallaboa, Puerto Rico
  14. 2.8 5 km SSE of Corozal, Puerto Rico
  15. 3.0 1 km NW of Potala Pastillo, 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.