QuakeIndex

Earthquake · reviewed by a seismologist

M 1.9md

Earthquake near San Sebastián, PR

No earthquake was likely felt in San Sebastián in the 24 hours to 6:10 am AST (10:10 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 1.9 earthquake was recorded 4 km (2 mi) southwest of San Sebastián, PR, at 4:26 pm AST on 28 September 2019 (20:26 UTC), 16 km deep.

USGS: 3 km SW of San Sebastián, Puerto Rico

19 km (11 mi) NE of Mayagüez, PR · 101 km (63 mi) W of San Juan, PR

4:26 pm AST, Sep 28, 2019 · · 16 km deep · released about 25 lb of TNT

Every earthquake near San Sebastián Felt it? Tell USGS Check my area
10 km30 km60 km120 km N San Sebastián Municipio 5 kmMoca Municipio 9 kmLas Marías Municipio 11 kmAñasco Municipio 13 kmLares Municipio 16 kmMaricao Municipio 18 kmIsabela Municipio 18 kmAguada Municipio 19 kmQuebradillas Municipio 19 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
4:26 pm AST on 28 September 2019 ()
Where
4 km (2 mi) southwest of San Sebastián, PR · earthquakes near San Sebastián
Magnitude
M 1.9 (md)
Depth
16 km below the surface
Felt
no reports yet
Nearest
San Sebastián Municipio, 5 km ENE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2600 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth it was probably too small to be felt, even directly above it. 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.

Earthquakes near other towns within 30 km: Juncal, Espino, Moca, Añasco, Las Marias, Aceitunas.

How big was it?

This earthquake released about 25 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.9 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 620,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 440,000× the energy of this one
  3. Around the size people start to feel M 3.0 39× the energy of this one
  4. This earthquake M 1.9 about 25 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 4.3 on 2019-09-05 — about 3,500 times the energy of this one.

Before 2016, the USGS record lists 8 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.1 24 km NNW of San Antonio, Puerto Rico · 46 km NNW of this epicentre
  2. 6.3 6 km WNW of Aguadilla, Puerto Rico · 25 km WNW of this epicentre
  3. 6.1 15 km WNW of San Antonio, Puerto Rico · 34 km NW of this epicentre
  4. 6.1 18 km NNW of San Antonio, Puerto Rico · 39 km NNW of this epicentre
  5. 5.8 4 km E of Moca, Puerto Rico · 11 km NNW 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 18.3186, -67.0176. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
San Sebastián Municipio, PR 5 km (3 mi) ENE earthquakes near San Sebastián Municipio
Moca Municipio, PR 9 km (6 mi) NW earthquakes near Moca Municipio
Las Marías Municipio, PR 11 km (7 mi) SSE earthquakes near Las Marías Municipio
Añasco Municipio, PR 13 km (8 mi) WSW earthquakes near Añasco Municipio
Lares Municipio, PR 16 km (10 mi) ESE earthquakes near Lares Municipio
Maricao Municipio, PR 18 km (11 mi) SSE earthquakes near Maricao Municipio

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

Aftershocks so far

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

  1. 2.4 7 km ESE of Maricao, Puerto Rico
  2. 1.8 12 km N of Yauco, Puerto Rico
  3. 1.6 11 km SE of La Parguera, Puerto Rico
  4. 1.8 7 km WNW of Puerto Real, Puerto Rico
  5. 2.3 7 km WSW of Guánica, Puerto Rico
  6. 1.6 3 km WSW of Fuig, Puerto Rico
  7. 1.9 2 km SW of Adjuntas, Puerto Rico
  8. 2.0 2 km NNE of Sabana Grande, Puerto Rico
  9. 1.8 4 km WNW of Hormigueros, Puerto Rico
  10. 2.6 4 km NNE of Isabela, Puerto Rico
  11. 1.6 6 km WSW of Guánica, Puerto Rico
  12. 1.5 3 km WNW of Palmarejo, Puerto Rico
  13. 2.3 8 km NW of Caban, Puerto Rico
  14. 2.0 3 km SW of San Sebastián, Puerto Rico
  15. 2.4 25 km NW of Aguadilla, 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.