QuakeIndex

Earthquake · reviewed by a seismologist

M 2.5md

Earthquake near San Sebastián, PR

No earthquake was likely felt in San Sebastián in the 24 hours to 3:38 am AST (07:38 UTC). The last one was M 3.4, 50 km (31 mi) N, at 9:00 pm AST on 27 October 2026, estimated intensity II (weak) in town. Every earthquake near San Sebastián

This page: a magnitude 2.5 earthquake was recorded 4 km (2 mi) south-southeast of San Sebastián, PR, at 11:56 pm AST on 17 January 2021 (03:56 UTC), 19 km deep.

USGS: 3 km SSE of San Sebastián, Puerto Rico

97 km (60 mi) W of San Juan, PR · 21 km (13 mi) ENE of Mayagüez, PR

11:56 pm AST, Jan 17, 2021 · · 19 km deep · released about 190 lb of TNT

Every earthquake near San Sebastián Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Sebastián Municipio 3 kmLas Marías Municipio 8 kmLares Municipio 12 kmMoca Municipio 14 kmMaricao Municipio 15 kmAñasco Municipio 16 kmQuebradillas Municipio 19 kmCamuy Municipio 20 kmIsabela Municipio 21 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
11:56 pm AST on 17 January 2021 ()
Where
4 km (2 mi) south-southeast of San Sebastián, PR · earthquakes near San Sebastián
Magnitude
M 2.5 (md)
Depth
19 km below the surface
Felt
no reports yet
Nearest
San Sebastián Municipio, 3 km NNE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1945 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 13 km (8 mi) from the epicentre. In San Sebastián, 4 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: San Sebastián 4 km, intensity II · Lares 11 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 190 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 78,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 55,000× the energy of this one
  3. Around the size people start to feel M 3.0 4.9× the energy of this one
  4. This earthquake M 2.5 about 190 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 6.4 on 2020-01-07 — about 620,000 times the energy of this one.

Before 2016, the USGS record lists 7 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.1 24 km NNW of San Antonio, Puerto Rico · 50 km NNW of this epicentre
  2. 6.3 6 km WNW of Aguadilla, Puerto Rico · 29 km WNW of this epicentre
  3. 6.1 15 km WNW of San Antonio, Puerto Rico · 39 km NW of this epicentre
  4. 6.1 18 km NNW of San Antonio, Puerto Rico · 43 km NNW of this epicentre
  5. 5.8 4 km E of Moca, Puerto Rico · 15 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 18.3030, -66.9765. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
San Sebastián Municipio, PR 3 km (2 mi) NNE earthquakes near San Sebastián Municipio
Las Marías Municipio, PR 8 km (5 mi) S earthquakes near Las Marías Municipio
Lares Municipio, PR 12 km (7 mi) ESE earthquakes near Lares Municipio
Moca Municipio, PR 14 km (9 mi) NW earthquakes near Moca Municipio
Maricao Municipio, PR 15 km (9 mi) SSE earthquakes near Maricao Municipio
Añasco Municipio, PR 16 km (10 mi) W earthquakes near Añasco Municipio

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

Aftershocks so far

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

  1. 1.9 4 km SE of Maria Antonia, Puerto Rico
  2. 1.8 5 km SW of Guánica, Puerto Rico
  3. 2.5 6 km SSE of Maria Antonia, Puerto Rico
  4. 1.8 11 km SSE of Guánica, Puerto Rico
  5. 1.9 3 km SW of Indios, Puerto Rico
  6. 2.0 2 km WSW of Indios, Puerto Rico
  7. 2.5 7 km SSE of Maria Antonia, Puerto Rico
  8. 2.3 11 km SSE of Guánica, Puerto Rico
  9. 1.7 4 km ESE of La Parguera, Puerto Rico
  10. 2.2 9 km SSE of Guánica, Puerto Rico
  11. 1.7 5 km WSW of Fuig, Puerto Rico
  12. 1.8 3 km SW of Indios, Puerto Rico
  13. 1.6 2 km E of Palomas, Puerto Rico
  14. 1.6 6 km WSW of Guánica, Puerto Rico
  15. 2.3 0 km S of Indios, 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.