QuakeIndex

Earthquake · reviewed by a seismologist

M 2.8md

Mona Passage

Yes. A magnitude 2.8 earthquake was recorded in Mona Passage, 12 km (8 mi) SW of Mayagüez, PR, at 12:49 am AST on 21 December 2021 (04:49 UTC), 19 km deep.

12 km (8 mi) SW of Mayagüez, PR · 125 km (78 mi) WSW of San Juan, PR

· 19 km deep · released about 450 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Hormigueros Municipio 10 kmCabo Rojo Municipio 13 kmSan Germán Municipio 18 kmAñasco Municipio 21 kmLajas Municipio 23 kmRincón Municipio 26 kmLas Marías Municipio 27 kmSabana Grande Municipio 28 kmAguada Municipio 30 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 2.8 (md)
Depth
19 km below the surface
Felt
no reports yet
Nearest
Hormigueros Municipio, 10 km ENE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1787 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 19 km (12 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: Puerto Real 5 km, intensity II · Mayagüez 12 km, intensity II · Pole Ojea 15 km, intensity II · San Germán 17 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 450 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 34,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 24,000× the energy of this one
  3. Around the size people start to feel M 3.0 2.1× the energy of this one
  4. This earthquake M 2.8 about 450 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 in our catalogue was M 6.4 on 2020-01-07 — about 270,000 times the energy of this one.

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 18.1110, -67.2070. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Hormigueros Municipio, PR 10 km (6 mi) ENE earthquakes near Hormigueros Municipio
Cabo Rojo Municipio, PR 13 km (8 mi) SSE earthquakes near Cabo Rojo Municipio
San Germán Municipio, PR 18 km (11 mi) E earthquakes near San Germán Municipio
Añasco Municipio, PR 21 km (13 mi) NNE earthquakes near Añasco Municipio
Lajas Municipio, PR 23 km (14 mi) SE earthquakes near Lajas Municipio
Rincón Municipio, PR 26 km (16 mi) N earthquakes near Rincón Municipio

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

Aftershocks so far

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

  1. 2.5 3 km SE of Maria Antonia, Puerto Rico
  2. 2.7 Puerto Rico region
  3. 2.7 3 km SW of Indios, Puerto Rico
  4. 2.3 0 km SSW of Fuig, Puerto Rico
  5. 2.9 7 km S of Indios, Puerto Rico
  6. 2.9 18 km S of Guánica, Puerto Rico
  7. 2.3 6 km SSW of Indios, Puerto Rico
  8. 2.6 4 km S of Guánica, Puerto Rico
  9. 2.1 4 km SSW of Indios, Puerto Rico
  10. 2.3 6 km SSW of Guánica, Puerto Rico
  11. 2.0 6 km E of La Parguera, Puerto Rico
  12. 2.6 4 km SW of La Parguera, Puerto Rico
  13. 2.5 4 km SW of Guánica, Puerto Rico
  14. 2.3 2 km E of Maria Antonia, Puerto Rico
  15. 2.4 7 km SSE of Maria Antonia, 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.