QuakeIndex

Earthquake · reviewed by a seismologist

M 3.1md

Earthquake near Emajagua, PR

Yes: an earthquake was likely felt in Emajagua in the last 24 hours. M 2.9, 23 km (14 mi) SE of Emajagua, at 5:20 pm AST on 11 November 2026 (21:20 UTC); the estimated shaking in Emajagua was intensity II (weak). 1 person has reported feeling it to USGS. Every earthquake near Emajagua

This page: a magnitude 3.1 earthquake was recorded 3 km (2 mi) southeast of Emajagua, PR, at 7:01 am AST on 3 October 2021 (11:01 UTC), 9.0 km deep. 3 people have reported feeling it to USGS.

USGS: 2 km SE of Emajagua, Puerto Rico

51 km (32 mi) SSE of San Juan, PR · 33 km (21 mi) SE of Caguas, PR

7:01 am AST, Oct 3, 2021 · · 9.0 km deep · released about 1,200 lb of TNT

Every earthquake near Emajagua Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Maunabo Municipio 4 kmYabucoa Municipio 8 kmPatillas Municipio 13 kmHumacao Municipio 18 kmArroyo Municipio 19 kmSan Lorenzo Municipio 22 kmLas Piedras Municipio 22 kmJuncos Municipio 27 kmNaguabo Municipio 28 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
7:01 am AST on 3 October 2021 ()
Where
3 km (2 mi) southeast of Emajagua, PR · earthquakes near Emajagua
Magnitude
M 3.1 (md)
Depth
9.0 km below the surface
Felt
3 reports · strongest reported intensity III
Nearest
Maunabo Municipio, 4 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 39 km (24 mi) from the epicentre. In Emajagua, 3 km away, the estimate is intensity III (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: Emajagua 3 km, intensity III · Humacao 19 km, intensity II · Jagual 24 km, intensity II · Guayama 27 km, intensity II · Caguas 34 km, intensity II · Cayey 35 km, intensity II · Aguas Claras 37 km, intensity II · Sumidero 38 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 1,200 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 6.7 280,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 12,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 8,800× the energy of this one
  4. This earthquake M 3.1 about 1,200 lb of TNT
  5. Around the size people start to feel M 3.0 this one released 1.3× 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 2016-12-05 — about 200 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 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 17.9860, -65.8610. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Maunabo Municipio, PR 4 km (3 mi) WNW earthquakes near Maunabo Municipio
Yabucoa Municipio, PR 8 km (5 mi) N earthquakes near Yabucoa Municipio
Patillas Municipio, PR 13 km (8 mi) W earthquakes near Patillas Municipio
Humacao Municipio, PR 18 km (11 mi) NNE earthquakes near Humacao Municipio
Arroyo Municipio, PR 19 km (12 mi) W earthquakes near Arroyo Municipio
San Lorenzo Municipio, PR 22 km (13 mi) NW earthquakes near San Lorenzo Municipio

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

Aftershocks so far

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

  1. 3.0 2 km N of Yaurel, Puerto Rico
  2. 1.8 19 km SW of Esperanza, Puerto Rico
  3. 2.8 0 km SW of Pastos, Puerto Rico
  4. 2.1 5 km SSE of Palmas, Puerto Rico
  5. 3.1 3 km N of Olimpo, Puerto Rico
  6. 1.9 0 km E of Salinas, Puerto Rico
  7. 2.4 1 km SSE of Salinas, Puerto Rico
  8. 3.0 0 km W of Sumidero, Puerto Rico
  9. 2.7 8 km SE of Esperanza, Puerto Rico
  10. 2.5 23 km SW of Esperanza, Puerto Rico
  11. 3.3 1 km ESE of Guaynabo, Puerto Rico
  12. 2.1 7 km SE of Esperanza, Puerto Rico
  13. 2.3 13 km SSE of Esperanza, Puerto Rico
  14. 2.7 6 km SSE of Salinas, Puerto Rico
  15. 2.6 6 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.