QuakeIndex

Earthquake · reviewed by a seismologist

M 3.0md

Earthquake near Emajagua, PR

No earthquake was likely felt in Emajagua in the 24 hours to 3:14 pm AST (19:14 UTC). The last one was M 2.2, 7 km (5 mi) ESE, at 2:59 pm AST on 4 November 2026, estimated intensity II (weak) in town. Every earthquake near Emajagua

This page: a magnitude 3.0 earthquake was recorded 30 km (19 mi) southeast of Emajagua, PR, at 7:12 pm AST on 4 August 2021 (23:12 UTC), 10 km deep.

USGS: 29 km SE of Emajagua, Puerto Rico

77 km (48 mi) SSE of San Juan, PR · 60 km (37 mi) SE of Caguas, PR

7:12 pm AST, Aug 4, 2021 · · 10 km deep · released about 1,100 lb of TNT

Every earthquake near Emajagua Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Maunabo Municipio 31 kmYabucoa Municipio 33 kmHumacao Municipio 37 kmPatillas Municipio 39 kmVieques Municipio 42 kmArroyo Municipio 43 kmNaguabo Municipio 43 kmLas Piedras Municipio 46 kmCeiba Municipio 48 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
7:12 pm AST on 4 August 2021 ()
Where
30 km (19 mi) southeast of Emajagua, PR · earthquakes near Emajagua
Magnitude
M 3.0 (md)
Depth
10 km below the surface
Felt
no reports yet
Nearest
Maunabo Municipio, 31 km NW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1925 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 38 km (24 mi) from the epicentre. In Emajagua, 30 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.

Likely felt in: Emajagua 30 km, intensity II · Esperanza 37 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 1,100 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.0 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 300,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 13,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 9,400× the energy of this one
  4. This earthquake M 3.0 about 1,100 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 210 times the energy of this one.

Before 2016, the USGS record lists one earthquake of M5 or more within 50 km:

  1. 5.3 68 km SSE of Emajagua, Puerto Rico · 48 km S 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 17.8258, -65.6668. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Maunabo Municipio, PR 31 km (19 mi) NW earthquakes near Maunabo Municipio
Yabucoa Municipio, PR 33 km (21 mi) NW earthquakes near Yabucoa Municipio
Humacao Municipio, PR 37 km (23 mi) NNW earthquakes near Humacao Municipio
Patillas Municipio, PR 39 km (24 mi) WNW earthquakes near Patillas Municipio
Vieques Municipio, PR 42 km (26 mi) NE earthquakes near Vieques Municipio
Arroyo Municipio, PR 43 km (27 mi) WNW earthquakes near Arroyo 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. 3.3 27 km SSE of Jobos, Puerto Rico
  2. 2.8 17 km SSE of Esperanza, Puerto Rico
  3. 2.5 23 km S of Arroyo, Puerto Rico
  4. 2.0 5 km ESE of Jobos, Puerto Rico
  5. 3.0 54 km S of Emajagua, Puerto Rico
  6. 2.3 1 km WNW of Esperanza, Puerto Rico
  7. 2.5 22 km SSW of Esperanza, Puerto Rico
  8. 3.7 15 km SE of Esperanza, Puerto Rico
  9. 2.2 7 km SSE of Lamboglia, Puerto Rico
  10. 3.0 13 km SE of Esperanza, Puerto Rico
  11. 2.2 3 km N of Yaurel, Puerto Rico
  12. 3.0 2 km N of Yaurel, Puerto Rico
  13. 1.8 19 km SW of Esperanza, Puerto Rico
  14. 3.2 18 km SE of Esperanza, Puerto Rico
  15. 2.1 5 km SSE of Palmas, 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.