QuakeIndex

Earthquake · reviewed by a seismologist

M 3.5md

Mona Passage

Yes. A magnitude 3.5 earthquake was recorded in Mona Passage, 52 km (32 mi) NW of Mayagüez, PR, at 1:22 pm AST on 12 December 2021 (17:22 UTC), 9.0 km deep. 1 person has reported feeling it to USGS.

52 km (32 mi) NW of Mayagüez, PR · 145 km (90 mi) W of San Juan, PR

· 9.0 km deep · released about 3 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Aguadilla Municipio 32 kmRincón Municipio 33 kmAguada Municipio 34 kmMoca Municipio 43 kmIsabela Municipio 45 kmAñasco Municipio 46 kmQuebradillas Municipio 54 kmSan Sebastián Municipio 56 kmHormigueros Municipio 60 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 3.5 (md)
Depth
9.0 km below the surface
Felt
1 report · strongest reported intensity II
Nearest
Aguadilla Municipio, 32 km ESE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1721 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 64 km (40 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: Rincón 33 km, intensity II · Aguadilla 34 km, intensity II · Aguada 34 km, intensity II · Rafael Hernandez 39 km, intensity II · Isabela 44 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 3 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 57,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 2,500× the energy of this one
  3. Magna, Utah 2020 M 5.7 1,800× the energy of this one
  4. This earthquake M 3.5 about 3 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 6.2× 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 in our catalogue was M 4.6 on 2020-01-29 — about 40 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 18.5831, -67.4290. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Aguadilla Municipio, PR 32 km (20 mi) ESE earthquakes near Aguadilla Municipio
Rincón Municipio, PR 33 km (21 mi) SE earthquakes near Rincón Municipio
Aguada Municipio, PR 34 km (21 mi) SE earthquakes near Aguada Municipio
Moca Municipio, PR 43 km (27 mi) ESE earthquakes near Moca Municipio
Isabela Municipio, PR 45 km (28 mi) ESE earthquakes near Isabela Municipio
Añasco Municipio, PR 46 km (28 mi) SE earthquakes near Añasco Municipio

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

Aftershocks so far

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

  1. 3.0 62 km NW of San Antonio, Puerto Rico
  2. 2.6 39 km NW of San Antonio, Puerto Rico
  3. 3.2 67 km NW of San Antonio, Puerto Rico
  4. 2.4 6 km W of Mayagüez, Puerto Rico
  5. 3.4 39 km WSW of Stella, Puerto Rico
  6. 3.3 21 km SW of Stella, Puerto Rico
  7. 3.2 39 km NW of San Antonio, Puerto Rico
  8. 3.1 2 km ESE of La Playa, Puerto Rico
  9. 2.2 21 km SW of Stella, Puerto Rico
  10. 3.2 20 km NW of San Antonio, Puerto Rico
  11. 3.2 37 km NW of San Antonio, Puerto Rico
  12. 2.7 5 km SSW of La Playa, Puerto Rico
  13. 3.4 4 km SSW of La Playa, Puerto Rico
  14. 2.4 35 km NW of Rincón, Puerto Rico
  15. 1.9 38 km WNW of Rincón, 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.