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M3.4 earthquake 133 km NNE of Loíza, Puerto Rico

A magnitude 3.4 earthquake struck 133 km NNE of Loíza, Puerto Rico at 23:23 local time (03:23 UTC) on 12 Sept 2026, at a depth of 8 km, according to USGS.

Data: USGS · updated 2026-09-13 05:15 UTC · reviewed

Magnitude
3.4minor
duration magnitude (md)
Depth
7.9 km
Status
Reviewed
Origin time
2026-09-13 03:23:41 UTC
Local: 12 Sept 2026, 23:23:41 (America/Puerto Rico)
Epicentre
19.511° N, 65.345° W

Circles show this event and others within 30 km from 7 days before to 30 days after. Lines: plate boundaries and GEM active faults. Open on the live map

Nearby places

Distance and estimated shaking at nearby places
PlaceDistanceEst. shaking
LoízaPuerto Rico · pop. 4,311133 kmINot felt
LuquilloPuerto Rico · pop. 8,326133 kmINot felt
FajardoPuerto Rico · pop. 32,124135 kmINot felt
Charlotte AmalieSaint Thomas Island, U.S. Virgin Islands · pop. 20,000137 kmINot felt
San JuanPuerto Rico · pop. 418,140141 kmINot felt
CarolinaPuerto Rico · pop. 170,404141 kmINot felt

Shaking is an estimate from the intensity prediction equation of Allen, Wald & Worden (2012), not an observation. Local ground and buildings can change it by a level or more. Likely felt out to about 22 km.

Every agency's solution

Agencies locate earthquakes with their own stations and methods, so their numbers differ. We match reports of the same event by time, distance and magnitude and show them side by side. The headline uses USGS · PR, which has been reviewed by an analyst.

AgencyMagnitudeDepthEpicentreTime offsetStatus
USGS · PRheadlinePuerto Rico Seismic Network via U.S. Geological Survey3.4 md7.9 km19.51° N, 65.34° W–Reviewed

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How big was it?

Often felt by people at rest close to the epicentre, rarely causes damage.

It released roughly the energy of 1.9 t of TNT. Magnitude is logarithmic: each whole step means about 32 times more energy and 10 times larger waves on a seismogram. Depth matters too: at 8 km this was a shallow earthquake, which is felt more strongly at the surface than a deeper one of the same size.

M3.4 releases about 32× the energy of M2.4, and its waves are about 10× taller on a seismogram. Energy: 1.9 t of TNT vs 60 kg of TNT.

Each square is the energy of one M2.4. Energy from log₁₀E = 1.5M + 4.8.

Aftershocks and nearby activity

5 later earthquakes within 30 km; the largest was M3.5 15 days ago. 6 in the 7 days before. Aftershock rates usually fall off roughly in proportion to 1/time.

Aftershocks

Mainshock M3.4

5 later earthquakes nearby. Aftershock rates typically fall off roughly as 1/time (Omori's law).

Aftershocks
Time after mainshock (hours)MagnitudeDepth (km)
7.603.516
10.713.280
90.823.418
196.493.376
231.923.312
  1. 3.5139 km NNE of Luquillo, Puerto Rico09-13 10:59
  2. 3.4118 km N of Charlotte Amalie, Saint Thomas Island, U.S. Virgin Islands09-16 22:12
  3. 3.3135 km NNE of Loíza, Puerto Rico09-22 19:18
  4. 3.3105 km NNE of Luquillo, Puerto Rico09-21 07:53
  5. 3.2124 km N of Culebra, Puerto Rico09-13 14:06

Did you feel it?

Reports from people help show where shaking was strong. They are anonymous and shown here in aggregate.

Reports close 14 days after an earthquake.

Reports on SeismoAtlas

No reports yet.

Event id pr71531608. First recorded here 28 Sept 2026, 17:32:11 UTC. Solutions: USGS · PR (usgs:pr71531608). Cite as: SeismoAtlas, “M3.4 earthquake 133 km NNE of Loíza, Puerto Rico”, https://seismoatlas.com/earthquake/pr71531608-m3-4-earthquake-133-km-nne-of-loiza-puerto-rico, data from USGS.

JSON: /api/v1/events/pr71531608. SeismoAtlas is not an official warning service.