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M3.4 earthquake 5 km W of Guánica, Puerto Rico

A magnitude 3.4 earthquake struck 5 km W of Guánica, Puerto Rico at 13:20 local time (17:20 UTC) on 18 Sept 2026, at a depth of 6 km, according to USGS.

1 reports to USGS “Did You Feel It?”

Data: USGS · updated 2026-09-25 18:15 UTC · reviewed

Magnitude
3.4minor
local magnitude (Richter) (ml)
Depth
6 km
Status
Reviewed
Origin time
2026-09-18 17:20:42 UTC
Local: 18 Sept 2026, 13:20:42 (America/Puerto Rico)
Epicentre
17.966° N, 66.960° 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
GuánicaPuerto Rico · pop. 9,2245 kmIVLight
Sabana GrandePuerto Rico · pop. 8,96113 kmIIIWeak
YaucoPuerto Rico · pop. 20,29514 kmIIIWeak
MayagüezPuerto Rico · pop. 73,07732 kmIIWeak
PoncePuerto Rico · pop. 137,49136 kmIIWeak
AreciboPuerto Rico · pop. 87,75462 kmINot felt
San JuanPuerto Rico · pop. 418,140106 kmINot felt
Santo Domingo EsteSanto Domingo Province, Dominican Republic · pop. 700,000311 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 23 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 ml6 km17.97° N, 66.96° W–Reviewed

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 6 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

51 later earthquakes within 30 km; the largest was M3.1 9 days ago. 13 in the 7 days before. Aftershock rates usually fall off roughly in proportion to 1/time.

Aftershocks

Mainshock M3.4

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

Aftershocks
Time after mainshock (hours)MagnitudeDepth (km)
1.052.88
1.062.56
2.072.76
2.133.07
4.342.58
4.922.57
5.122.67
9.862.59
9.882.513
10.222.57
11.473.07
11.773.18
12.183.18
23.182.88
29.432.69
30.892.57
51.203.08
54.302.57
79.172.111
79.712.215
83.752.017
92.411.811
93.392.17
94.421.87
98.002.28
103.722.18
105.882.27
107.582.117
108.922.57
119.681.78
120.932.314
123.512.18
123.592.37
125.932.08
130.181.99
145.922.112
148.022.68
148.922.46
150.962.37
160.932.09
163.672.17
187.162.49
192.332.18
202.222.16
204.751.27
204.762.08
204.761.27
205.082.37
226.031.77
230.282.27
239.782.017
  1. 3.15 km SW of Guánica, Puerto Rico09-19 05:06
  2. 3.15 km W of Guánica, Puerto Rico09-19 05:31
  3. 3.05 km WSW of Guánica, Puerto Rico09-18 19:28
  4. 3.04 km SW of Guánica, Puerto Rico09-19 04:49
  5. 3.05 km WSW of Guánica, Puerto Rico09-20 20:32
  6. 2.84 km WSW of Guánica, Puerto Rico09-18 18:23
  7. 2.8Near Guánica, Puerto Rico09-19 16:31
  8. 2.75 km W of Guánica, Puerto Rico09-18 19:24
  9. 2.67 km SW of Guánica, Puerto Rico09-24 21:21
  10. 2.65 km SW of Guánica, Puerto Rico09-19 22:46
  11. 2.65 km WSW of Guánica, Puerto Rico09-18 22:28
  12. 2.5Near Guánica, Puerto Rico09-18 21:41
  13. 2.55 km SSW of Guánica, Puerto Rico09-18 18:24
  14. 2.54 km W of Guánica, Puerto Rico09-20 00:13
  15. 2.55 km SW of Guánica, Puerto Rico09-23 06:15
  16. 2.54 km W of Guánica, Puerto Rico09-20 23:38
  17. 2.54 km SSW of Guánica, Puerto Rico09-19 03:13
  18. 2.54 km SW of Guánica, Puerto Rico09-19 03:33
  19. 2.54 km SW of Guánica, Puerto Rico09-19 03:12
  20. 2.55 km SW of Guánica, Puerto Rico09-18 22:15
  21. 2.45 km WSW of Guánica, Puerto Rico09-24 22:16
  22. 2.44 km SE of Guánica, Puerto Rico09-26 12:30
  23. 2.3Near Guayanilla, Puerto Rico09-23 18:16
  24. 2.34 km W of Guánica, Puerto Rico09-25 00:18
  25. 2.34 km SW of Guánica, Puerto Rico09-23 20:55

Did you feel it?

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Reports on SeismoAtlas

No reports yet.

USGS “Did You Feel It?” has 1 reports: add yours at USGS.

Event id pr2026261002. First recorded here 28 Sept 2026, 17:32:11 UTC. Solutions: USGS · PR (usgs:pr2026261002). Cite as: SeismoAtlas, “M3.4 earthquake 5 km W of Guánica, Puerto Rico”, https://seismoatlas.com/earthquake/pr2026261002-m3-4-earthquake-5-km-w-of-guanica-puerto-rico, data from USGS.

JSON: /api/v1/events/pr2026261002. SeismoAtlas is not an official warning service.