QuakeIndex

Earthquake · reviewed by a seismologist

M 3.1md

51 km N of Dorado, Puerto Rico

Yes. A magnitude 3.1 earthquake was recorded 51 km N of Dorado, Puerto Rico, 60 km (37 mi) NNW of San Juan, PR, at 11:28 am AST on 21 September 2020 (15:28 UTC), 14 km deep. 1 person has reported feeling it to USGS.

60 km (37 mi) NNW of San Juan, PR

· 14 km deep · released about 1,200 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Dorado Municipio 50 kmToa Baja Municipio 52 kmCataño Municipio 54 kmVega Baja Municipio 55 kmVega Alta Municipio 55 kmSan Juan Municipio 58 kmManatí Municipio 60 kmLoíza Municipio 61 kmBarceloneta Municipio 61 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 3.1 (md)
Depth
14 km below the surface
Felt
1 report · strongest reported intensity II
Nearest
Dorado Municipio, 50 km S
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1556 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. 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 1,200 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 4.8 on 2017-08-18 — about 390 times the energy of this one.

Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:

  1. 5.7 78 km N of Tierras Nuevas Poniente, Puerto Rico · 44 km NW of this epicentre
  2. 5.5 64 km N of Tierras Nuevas Poniente, Puerto Rico · 30 km WNW of this epicentre
  3. 5.1 66 km N of Brenas, Puerto Rico · 22 km NW of this epicentre
  4. 5.0 3 km N of Brenas, Puerto Rico · 48 km SSW 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 18.9228, -66.2251. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Dorado Municipio, PR 50 km (31 mi) S earthquakes near Dorado Municipio
Toa Baja Municipio, PR 52 km (32 mi) S earthquakes near Toa Baja Municipio
Cataño Municipio, PR 54 km (33 mi) S earthquakes near Cataño Municipio
Vega Baja Municipio, PR 55 km (34 mi) SSW earthquakes near Vega Baja Municipio
Vega Alta Municipio, PR 55 km (34 mi) SSW earthquakes near Vega Alta Municipio
San Juan Municipio, PR 58 km (36 mi) SSE earthquakes near San Juan Municipio

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

Aftershocks so far

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

  1. 3.3 85 km N of Tierras Nuevas Poniente, Puerto Rico
  2. 3.3 84 km N of Tierras Nuevas Poniente, Puerto Rico
  3. 3.1 61 km NNE of Arecibo, Puerto Rico
  4. 3.2 71 km N of Brenas, Puerto Rico
  5. 3.1 72 km N of Brenas, Puerto Rico
  6. 3.3 49 km N of Brenas, Puerto Rico
  7. 2.9 76 km NNE of San Juan, Puerto Rico
  8. 3.4 64 km N of Tierras Nuevas Poniente, Puerto Rico
  9. 3.0 54 km N of Brenas, Puerto Rico
  10. 3.2 75 km N of Tierras Nuevas Poniente, Puerto Rico
  11. 3.2 72 km N of Brenas, Puerto Rico
  12. 3.2 77 km N of Tierras Nuevas Poniente, Puerto Rico
  13. 3.0 34 km N of San Juan, Puerto Rico
  14. 3.0 53 km N of Brenas, Puerto Rico
  15. 3.0 75 km N of Tierras Nuevas Poniente, 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.