QuakeIndex

Earthquake · reviewed by a seismologist

M 3.5md

72 km SSE of Emajagua, Puerto Rico

Yes. A magnitude 3.5 earthquake was recorded 72 km SSE of Emajagua, Puerto Rico, at 9:53 am AST on 1 October 2021 (13:53 UTC), 47 km deep.

· 47 km deep · released about 2.3 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Maunabo Municipio 74 kmYabucoa Municipio 78 kmPatillas Municipio 79 kmArroyo Municipio 80 kmVieques Municipio 81 kmHumacao Municipio 84 kmGuayama Municipio 86 kmNaguabo Municipio 91 kmLas Piedras Municipio 92 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
Magnitude
M 3.5 (md)
Depth
47 km below the surface
Felt
no reports yet
Nearest
Maunabo Municipio, 74 km NNW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1867 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. 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.

How big was it?

This earthquake released about 2.3 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 72,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 3,200× the energy of this one
  3. Magna, Utah 2020 M 5.7 2,300× the energy of this one
  4. This earthquake M 3.5 about 2.3 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 4.9× 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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

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 · 15 km W 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 17.4113, -65.5743. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Maunabo Municipio, PR 74 km (46 mi) NNW earthquakes near Maunabo Municipio
Yabucoa Municipio, PR 78 km (49 mi) NNW earthquakes near Yabucoa Municipio
Patillas Municipio, PR 79 km (49 mi) NNW earthquakes near Patillas Municipio
Arroyo Municipio, PR 80 km (49 mi) NW earthquakes near Arroyo Municipio
Vieques Municipio, PR 81 km (50 mi) N earthquakes near Vieques Municipio
Humacao Municipio, PR 84 km (52 mi) NNW earthquakes near Humacao Municipio

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

Aftershocks so far

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

  1. 3.0 26 km SE of Emajagua, Puerto Rico
  2. 3.3 98 km SSE of Emajagua, Puerto Rico
  3. 3.2 54 km WSW of Saint Croix, U.S. Virgin Islands
  4. 3.0 30 km SSW of Esperanza, Puerto Rico
  5. 3.1 83 km SSE of Emajagua, Puerto Rico
  6. 3.1 30 km SE of Emajagua, Puerto Rico
  7. 2.9 29 km SSW of Esperanza, Puerto Rico
  8. 3.1 65 km SSE of Arroyo, Puerto Rico
  9. 3.4 83 km SW of Saint Croix, U.S. Virgin Islands
  10. 3.1 42 km SE of Emajagua, Puerto Rico
  11. 2.5 41 km SSE of Arroyo, Puerto Rico
  12. 3.3 77 km WSW of Saint Croix, U.S. Virgin Islands
  13. 2.6 37 km S of Esperanza, Puerto Rico
  14. 2.7 29 km SSW of Esperanza, Puerto Rico
  15. 2.9 28 km SE of Emajagua, 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.