QuakeIndex

Earthquake · reviewed by a seismologist

M 3.0md

Earthquake near Loíza, PR

No earthquake was likely felt in Loíza in the 24 hours to 11:31 am AST (15:31 UTC). The last one was M 4.1, 78 km (48 mi) SE, at 5:44 am AST on 28 October 2026, estimated intensity II (weak) in town; 5 felt reports to USGS. Every earthquake near Loíza

This page: a magnitude 3.0 earthquake was recorded 20 km (13 mi) north of Loíza, PR, at 12:59 am AST on 21 April 2018 (04:59 UTC), 64 km deep.

USGS: 20 km N of Loíza, Puerto Rico

30 km (19 mi) NE of San Juan, PR · 25 km (15 mi) NNE of Carolina, PR

12:59 am AST, Apr 21, 2018 · · 64 km deep · released about 890 lb of TNT

Every earthquake near Loíza Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Loíza Municipio 20 kmCarolina Municipio 26 kmRío Grande Municipio 28 kmSan Juan Municipio 29 kmCanóvanas Municipio 32 kmLuquillo Municipio 33 kmTrujillo Alto Municipio 33 kmCataño Municipio 34 kmToa Baja Municipio 37 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
12:59 am AST on 21 April 2018 ()
Where
20 km (13 mi) north of Loíza, PR · earthquakes near Loíza
Magnitude
M 3.0 (md)
Depth
64 km below the surface
Felt
no reports yet
Nearest
Loíza Municipio, 20 km SSW
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 3040 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 it was probably too small to be felt, even directly above it. In Loíza, 20 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: Suárez, Vieques, San Isidro, Santa Barbara, Canovanas, Río Grande.

How big was it?

This earthquake released about 890 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.0 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 380,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 17,000× the energy of this one
  3. Magna, Utah 2020 M 5.7 12,000× the energy of this one
  4. This earthquake M 3.0 about 890 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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:

  1. 5.1 3 km W of Aguas Buenas, Puerto Rico · 47 km SSW of this epicentre
  2. 5.0 3 km N of Brenas, Puerto Rico · 50 km WSW 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 18.6150, -65.8863. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Loíza Municipio, PR 20 km (12 mi) SSW earthquakes near Loíza Municipio
Carolina Municipio, PR 26 km (16 mi) SSW earthquakes near Carolina Municipio
Río Grande Municipio, PR 28 km (17 mi) SSE earthquakes near Río Grande Municipio
San Juan Municipio, PR 29 km (18 mi) SW earthquakes near San Juan Municipio
Canóvanas Municipio, PR 32 km (20 mi) S earthquakes near Canóvanas Municipio
Luquillo Municipio, PR 33 km (21 mi) SE earthquakes near Luquillo Municipio

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

Aftershocks so far

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

  1. 2.7 2 km E of La Fermina, Puerto Rico
  2. 2.3 3 km ENE of Bayamón, Puerto Rico
  3. 2.9 8 km NNW of Dorado, Puerto Rico
  4. 2.8 31 km N of San Juan, Puerto Rico
  5. 2.8 Puerto Rico region
  6. 1.7 1 km SE of Bayamón, Puerto Rico
  7. 2.8 4 km SE of Cataño, Puerto Rico
  8. 2.3 4 km N of Brenas, Puerto Rico
  9. 2.0 3 km SW of Guaynabo, Puerto Rico
  10. 2.6 31 km N of San Juan, Puerto Rico
  11. 2.5 4 km NNE of Guaynabo, Puerto Rico
  12. 2.1 44 km NNE of Luquillo, Puerto Rico
  13. 2.3 2 km SSW of Bayamón, Puerto Rico
  14. 2.5 12 km NNE of Brenas, Puerto Rico
  15. 2.8 2 km NW of Dorado, 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.