Swarm of 12 Quakes Fire Off 100 Miles from South Oregon Coast

Published 09/09/25 at 6:25 p.m.
By Oregon Coast Beach Connection Staff

(Port Orford, Oregon) – A string of 12 quakes have erupted off the south Oregon coast since Monday night, the first happening a little after 9 p.m. at a sizable magnitude 5.8. The rest that followed ranged in magnitude from 2.7 to 5.1.

No damage is reported and no tsunami threat is in the cards. This is not abnormal for the area to exhibit a swarm of quakes, but it does not happen often. At 5.8, the first one at 9:08 p.m. was sizable and a bit bigger than usual there. It was 8 miles beneath the surface and about 102 miles offshore.

The other quakes:

- M 5.1 – 181 km WSW of Port Orford, Oregon – 12:31:43 p.m. PDT
- M 4.4 – 162 km W of Port Orford, Oregon – 12:31:03 p.m. PDT
- M 4.9 – 181 km WSW of Port Orford, Oregon – 12:02:04 p.m. PDT
- M 3.6 – 218 km WSW of Port Orford, Oregon – 9:31:29 a.m. PDT
- M 2.7 – 135 km WSW of Port Orford, Oregon – 7:58:09 a.m. PDT
- M 4.3 – 184 km WSW of Port Orford, Oregon – 4:47:09 a.m. PDT
- M 3.1 – 173 km WSW of Port Orford, Oregon – 1:05:20 a.m. PDT
- M 4.9 – 167 km WSW of Port Orford, Oregon – 10:59:03 p.m. PDT (Sept 8)
- M 3.3 – 173 km WSW of Port Orford, Oregon – 9:38:58 p.m. PDT (Sept 8)
- M 2.7 – 166 km W of Gold Beach, Oregon – 9:32:41 p.m. PDT (Sept 8)
- M 4.4 – 174 km WSW of Port Orford, Oregon – 9:15:08 p.m. PDT (Sept 8)

All were in and around the same vicinity, which is typical of this grouping of faults.

Measurements of earthquake magnitudes are extremely wide, although the increments may appear small. A 7.0 is 1,000 times bigger than a 4.0, according to the USGS. But it is 31,622 times stronger in its release of energy.

There are many quakes in the area off Coos Bay, Bandon and Port Orford during the year, although 2025 has been not as active as most years.

Although a larger quake than usual off the Oregon coast, scientists say this is generally normal for what is known as the Blanco Fracture Zone, an area of fault lines and weak spots that is geologically quite active. You can see some of the uplifting action in the way the cliffs at Shore Acres tilt at an angle.

It is not directly connected to the Cascadia Subduction Zone, but it is a reminder that the big one will hit one day.

Such smaller quakes do not mean the area is releasing pressure, either, according to Seaside geologist Tom Horning.

See Live Earthquake, Tsunami Updates from Oregon Coast, Washington. B.C., California, Alaska

Horning said that here there's a lot of interaction between parts of the the Earth just beneath the offshore parts of Oregon's coastline.

“Other sides of the plate are where the smaller quakes are occurring with regularity,” Horning said. “However, these other parts of the plate boundary are having quakes regularly because of local geologic conditions that favor frequent events. Their locked interfaces stand vertically and are locked for only a few miles underground. It is easy for the plate movements to overwhelm these smaller locked zones, so frequent small quakes take place.”

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Recent Quake Stories (earlier this summer)

Oregon Coast Tsunami Findings: Port Orford Received Largest Wave at 2.4 ft
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