M2.5 earthquake 45 km SW of Fortuna, California, United States
A magnitude 2.5 earthquake struck 45 km SW of Fortuna, California, United States at 21:39 local time (04:39 UTC) on 17 Sept 2026, at a depth of 9 km, according to USGS.
revised from M2.6
Data: USGS · updated 2026-09-28 23:22 UTC · reviewed
- Magnitude
- 2.5micro
duration magnitude (md)
revised from 2.6 - Depth
- 9 km
- Status
- Reviewed
- Origin time
- 2026-09-18 04:39:53 UTC
- Local: 17 Sept 2026, 21:39:53 (America/Los Angeles)
- Epicentre
- 40.294° N, 124.500° 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
| Place | Distance | Est. shaking |
|---|---|---|
| FortunaCalifornia, United States · pop. 12,000 | 45 km | INot felt |
| EurekaCalifornia, United States · pop. 27,017 | 63 km | INot felt |
| SacramentoCalifornia, United States · pop. 524,943 | 321 km | INot felt |
| San FranciscoCalifornia, United States · pop. 827,526 | 333 km | INot felt |
| OaklandCalifornia, United States · pop. 419,267 | 338 km | INot felt |
| StocktonCalifornia, United States · pop. 305,658 | 380 km | INot felt |
| San JoseCalifornia, United States · pop. 997,368 | 399 km | INot 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 4 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 · NC, which has been reviewed by an analyst.
| Agency | Magnitude | Depth | Epicentre | Time offset | Status |
|---|---|---|---|---|---|
| USGS · NCheadlineNorthern California Seismic System via U.S. Geological Survey | 2.5 mdwas 2.6 | 9 km | 40.29° N, 124.50° W | – | Reviewed · 1 revision |
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How big was it?
Usually not felt. Recorded by nearby seismometers; thousands occur worldwide every day.
It released roughly the energy of 97 kg 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 9 km this was a shallow earthquake, which is felt more strongly at the surface than a deeper one of the same size.
M2.5 releases about 36× the energy of M1.5, and its waves are about 11× taller on a seismogram. Energy: 97 kg of TNT vs 3 kg of TNT.
Each square is the energy of one M1.5. Energy from log₁₀E = 1.5M + 4.8.
Aftershocks and nearby activity
6 later earthquakes within 30 km; the largest was M3.0 7 days ago. 2 in the 7 days before. Aftershock rates usually fall off roughly in proportion to 1/time.
Mainshock M2.5
6 later earthquakes nearby. Aftershock rates typically fall off roughly as 1/time (Omori's law).
| Time after mainshock (hours) | Magnitude | Depth (km) |
|---|---|---|
| 86.25 | 3.0 | 6 |
| 87.00 | 1.8 | 9 |
| 90.03 | 2.5 | 10 |
| 110.34 | 2.5 | 2 |
| 113.65 | 1.7 | 20 |
| 123.94 | 1.4 | 10 |
- 3.048 km SW of Fortuna, California, United States09-21 18:54
- 2.557 km WSW of Fortuna, California, United States09-22 19:00
- 2.546 km SW of Fortuna, California, United States09-21 22:41
- 1.840 km SW of Fortuna, California, United States09-21 19:39
- 1.741 km SW of Fortuna, California, United States09-22 22:18
- 1.442 km SW of Fortuna, California, United States09-23 08:36
Did you feel it?
Reports from people help show where shaking was strong. They are anonymous and shown here in aggregate.
Reports on SeismoAtlas
No reports yet.
Event id nc75437647. First recorded here 28 Sept 2026, 17:32:11 UTC. Solutions: USGS · NC (usgs:nc75437647). Cite as: SeismoAtlas, “M2.5 earthquake 45 km SW of Fortuna, California, United States”, https://seismoatlas.com/earthquake/nc75437647-m2-5-earthquake-45-km-sw-of-fortuna-california-united-states, data from USGS.
JSON: /api/v1/events/nc75437647. SeismoAtlas is not an official warning service.