M1.8 earthquake 8 km W of Longbranch, Washington
A magnitude 1.8 earthquake struck 8 km W of Longbranch, Washington on Mon, Mar 31, 1975, 6:26 PM PDT (01:26 UTC), 8 km (5 mi) below the surface.
A larger quake followed: M2.2 2 km NNE of Riverton, Washington. This one was a foreshock.
Map
Where this earthquake was located, with the others nearby. Select one for its page.
The earthquake
- Magnitude
- 1.8 (md), micro
- Local time
- UTC
- 1975-04-01 01:26:27 UTC
- Depth
- 7.6 km (4.7 mi), shallow
- Epicenter
- 47.196° N, 122.868° W
- Region
- Washington
- Tsunami flag
- No
- Status
- Reviewed by a seismologist
Did you feel it?
No one has reported feeling this quake to the USGS.
How well it is located
Reviewed by a seismologist.
- Location uncertainty
- About 0.4 km horizontally, 1.2 km in depth
- Magnitude uncertainty
- ±0.14
- Depth from
- From location
- Station coverage gap
- 182°, poorly surrounded by stations
- Stations used
- 6
Nearest places
Distance and direction from each place to the epicenter, with its forecast.
Nearby
Within 100 km, magnitude 1.5 and up: 8 in the 60 days after this one and 5 in the 30 days before it.
After
- 2.22 km NNE of Riverton, Washington · 18802 days ago · 25 km deep · 56 km away
- 3.711 km SW of Greenwater, Washington · 18793 days ago · 6 km deep · 86 km away
- 2.817 km ESE of Carbonado, Washington · 18793 days ago · -1 km deep · 80 km away
- 4.010 km SSW of Seabeck, Washington · 18787 days ago · 40 km deep · 40 km away
- 4.22 km SW of DuPont, Washington · 18781 days ago · 45 km deep · 20 km away
- 1.71 km NNE of Snoqualmie, Washington · 18752 days ago · 8 km deep · 88 km away
- 1.55 km S of Fall City, Washington · 18748 days ago · 18 km deep · 81 km away
- 1.75 km SSE of Keyport, Washington · 18745 days ago · 18 km deep · 55 km away
Before
- 2.13 km NE of Dash Point, Washington · 18804 days ago · 14 km deep · 40 km away
- 2.83 km NW of Black Diamond, Washington · 18815 days ago · 20 km deep · 65 km away
- 2.18 km WSW of Lofall, Washington · 18823 days ago · 19 km deep · 67 km away
- 1.918 km SSE of Carbonado, Washington · 18826 days ago · 6 km deep · 76 km away
- 2.05 km SW of Wilderness Rim, Washington · 18831 days ago · 19 km deep · 82 km away
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Sources
From the USGS Earthquake Hazards Program and its partner networks, event uw10860543. Read Tue, Sep 22, 2026, 5:15 PM UTC.