QuakeIndex

Earthquake · reviewed by a seismologist

M 3.4md

51 km NW of San Antonio, Puerto Rico

Yes. A magnitude 3.4 earthquake was recorded 51 km NW of San Antonio, Puerto Rico, at 4:35 pm AST on 5 April 2021 (20:35 UTC), 6.0 km deep. 1 person has reported feeling it to USGS.

· 6.0 km deep · released about 1.7 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Aguadilla Municipio 48 kmAguada Municipio 54 kmRincón Municipio 55 kmIsabela Municipio 59 kmMoca Municipio 61 kmAñasco Municipio 66 kmQuebradillas Municipio 68 kmSan Sebastián Municipio 73 kmCamuy Municipio 75 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 3.4 (md)
Depth
6.0 km below the surface
Felt
1 report · strongest reported intensity II
Nearest
Aguadilla Municipio, 48 km SE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1978 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 56 km (35 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 1.7 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.4 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 99,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 4,400× the energy of this one
  3. Magna, Utah 2020 M 5.7 3,100× the energy of this one
  4. This earthquake M 3.4 about 1.7 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 3.6× 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 6.0 on 2019-09-24 — about 8,800 times the energy of this one.

Before 2016, the USGS record lists 15 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.7 45 km N of San Antonio, Puerto Rico · 40 km ENE of this epicentre
  2. 7.1 24 km NNW of San Antonio, Puerto Rico · 32 km ESE of this epicentre
  3. 6.8 94 km NE of Punta Cana, Dominican Republic · 46 km NNW of this epicentre
  4. 6.4 32 km NW of Aguadilla, Puerto Rico · 21 km SSE of this epicentre
  5. 6.3 6 km WNW of Aguadilla, Puerto Rico · 47 km SE 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 18.7796, -67.4775. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Aguadilla Municipio, PR 48 km (30 mi) SE earthquakes near Aguadilla Municipio
Aguada Municipio, PR 54 km (34 mi) SE earthquakes near Aguada Municipio
Rincón Municipio, PR 55 km (34 mi) SSE earthquakes near Rincón Municipio
Isabela Municipio, PR 59 km (37 mi) SE earthquakes near Isabela Municipio
Moca Municipio, PR 61 km (38 mi) SE earthquakes near Moca Municipio
Añasco Municipio, PR 66 km (41 mi) SSE earthquakes near Añasco Municipio

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

Aftershocks so far

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

  1. 3.3 93 km NE of Punta Cana, Dominican Republic
  2. 3.2 48 km NNW of San Antonio, Puerto Rico
  3. 3.0 11 km NNW of Rincón, Puerto Rico
  4. 3.1 7 km WNW of Aguadilla, Puerto Rico
  5. 3.0 14 km NW of Rincón, Puerto Rico
  6. 3.2 49 km NNW of San Antonio, Puerto Rico
  7. 3.1 9 km N of San Antonio, Puerto Rico
  8. 3.1 57 km WNW of Rincón, Puerto Rico
  9. 3.4 15 km N of Isabela, Puerto Rico
  10. 3.5 51 km NNW of San Antonio, Puerto Rico
  11. 3.4 22 km NNW of Isabela, Puerto Rico
  12. 3.5 59 km N of San Antonio, Puerto Rico
  13. 3.5 40 km N of Isabela, Puerto Rico
  14. 3.4 70 km ENE of Punta Cana, Dominican Republic
  15. 3.1 86 km NE of Punta Cana, Dominican Republic

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.