QuakeIndex

Earthquake · reviewed by a seismologist

M 3.9ml

Earthquake near Guayanilla, PR

No earthquake was likely felt in Guayanilla in the 24 hours to 12:49 pm AST (16:49 UTC). The last one was M 2.1, in Guayanilla, at 4:39 pm AST on 9 November 2026, estimated intensity II (weak) in town. Every earthquake near Guayanilla

This page: a magnitude 3.9 earthquake was recorded in Guayanilla, PR, at 8:21 am AST on 7 January 2020 (12:21 UTC), 10 km deep. 4 people have reported feeling it to USGS.

USGS: 1 km NNW of Guayanilla, Puerto Rico

19 km (12 mi) W of Ponce, PR

8:21 am AST, Jan 7, 2020 · · 10 km deep · released about 10 tons of TNT

Every earthquake near Guayanilla Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Guayanilla Municipio 3 kmPeñuelas Municipio 7 kmYauco Municipio 9 kmGuánica Municipio 16 kmSabana Grande Municipio 17 kmAdjuntas Municipio 17 kmPonce Municipio 20 kmMaricao Municipio 22 kmLajas Municipio 26 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
8:21 am AST on 7 January 2020 ()
Where
in Guayanilla, PR · earthquakes near Guayanilla
Magnitude
M 3.9 (ml)
Depth
10 km below the surface
Felt
4 reports · strongest reported intensity V
Measured shaking
intensity III (ShakeMap)
Nearest
Guayanilla Municipio, 3 km S
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2426 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 88 km (55 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.

Likely felt in: Guayanilla in town, intensity IV · Magas Arriba 3 km, intensity IV · Yauco 6 km, intensity IV · Tallaboa 9 km, intensity III · Tallaboa Alta 11 km, intensity III · Adjuntas 17 km, intensity III · Ponce 18 km, intensity III · San Germán 27 km, intensity III. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 10 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.9 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 16,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 730× the energy of this one
  3. Magna, Utah 2020 M 5.7 520× the energy of this one
  4. This earthquake M 3.9 about 10 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 22× 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 6.4 on 2020-01-07 — about 5,800 times the energy of this one.

Before 2016, the USGS record since 1900 lists no earthquake of M5 or more within 50 km.

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 18.0291, -66.7975. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Guayanilla Municipio, PR 3 km (2 mi) S earthquakes near Guayanilla Municipio
Peñuelas Municipio, PR 7 km (5 mi) E earthquakes near Peñuelas Municipio
Yauco Municipio, PR 9 km (6 mi) NW earthquakes near Yauco Municipio
Guánica Municipio, PR 16 km (10 mi) SW earthquakes near Guánica Municipio
Sabana Grande Municipio, PR 17 km (11 mi) WNW earthquakes near Sabana Grande Municipio
Adjuntas Municipio, PR 17 km (11 mi) NNE earthquakes near Adjuntas Municipio

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

Aftershocks so far

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

  1. 2.0 7 km S of Tallaboa, Puerto Rico
  2. 1.8 1 km SSE of Guayanilla, Puerto Rico
  3. 1.8 2 km NNW of Magas Arriba, Puerto Rico
  4. 2.4 6 km SW of Tallaboa, Puerto Rico
  5. 1.8 8 km SSW of Guánica, Puerto Rico
  6. 2.8 1 km NNW of Magas Arriba, Puerto Rico
  7. 2.9 8 km SSE of Indios, Puerto Rico
  8. 1.8 7 km SSE of Guánica, Puerto Rico
  9. 2.2 6 km SW of Tallaboa, Puerto Rico
  10. 2.6 20 km SSW of Tallaboa, Puerto Rico
  11. 1.8 3 km WSW of Tallaboa, Puerto Rico
  12. 2.8 3 km NNW of Guayanilla, Puerto Rico
  13. 2.9 0 km NE of Guayanilla, Puerto Rico
  14. 1.9 2 km ESE of Magas Arriba, Puerto Rico
  15. 3.5 1 km W of Tallaboa, 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.