Reviewed by USGSCalifornia35y ago
M2.8 earthquake 44 km SW of Ferndale, California
Wednesday, September 25, 1991, 22:09:24 UTC · 40.313°N, 124.651°W
A magnitude 2.8 earthquake struck 44 km SW of Ferndale, California on Wednesday, September 25, 1991, 22:09:24 UTC, at a depth of 21.8 km (shallow).
- Magnitude
- 2.8
- Minor · md
- Depth
- 22 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 50 km aftershock search area
In context
How big was it, and why here?
Energy released
239 kg of TNT
That is about 1/63,000 of the Hiroshima bomb. A magnitude 5.0 releases about 1,995 times more energy.
Tectonic setting
0 km
from the nearest mapped plate boundary, between the North American and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
22 km
Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.
Did You Feel It?
Where it was felt
No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.
I felt it — report to USGS ↗USGS PAGER estimate
Who was exposed to shaking
USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.
After the main event
Aftershocks within 50 km
USGS lists 7 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M3.2 on October 20, 1991. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 3.225 km SW of Scotia, California35y ago · 29 km E of this epicenter
- 2.740 km SW of Ferndale, California35y ago · 5 km E of this epicenter
- 3.038 km SW of Ferndale, California35y ago · 8 km E of this epicenter
- 3.07 km SSE of Ferndale, California35y ago · 43 km NE of this epicenter
- 2.624 km SW of Scotia, California35y ago · 30 km E of this epicenter
- 3.0off the coast of Northern California35y ago · 42 km NW of this epicenter
- 2.875 km WSW of Ferndale, California35y ago · 43 km W of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 157 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.4123 km W of Big Lagoon, CaliforniaJanuary 31, 1922 · 126 km NW of this epicenter
- 7.2The 1980 Eureka, California EarthquakeNovember 8, 1980 · 96 km N of this epicenter
- 7.1The 1923 Humboldt County, California EarthquakeJanuary 22, 1923 · 38 km NW of this epicenter
- 7.0136 km WSW of Brookings, OregonAugust 17, 1991 · 183 km NW of this epicenter
- 6.9103 km W of Pistol River, OregonJuly 13, 1991 · 224 km N of this epicenter
- 6.8123 km W of Ferndale, CaliforniaNovember 25, 1954 · 91 km W of this epicenter
- 6.884 km W of Ferndale, CaliforniaFebruary 9, 1941 · 64 km NW of this epicenter
- 6.8off the coast of Northern CaliforniaJuly 6, 1934 · 122 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 17 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 3 recorded deaths. The most severe:
- 1969M4.8
Santa Rosa
2 Oct 1969 · 265 km away · intensity VIII
1 death$8 million damage
- 1954M6.6
Humboldt County
21 Dec 1954 · 87 km away
1 death$2 million damage
- 1932M6.5
Eureka
6 Jun 1932 · 56 km away · intensity VIII
1 deathModerate damage ($1–5M)
- 1980M7.2
North Coast
8 Nov 1980 · 96 km away · intensity VII
$2 million damage
- 1991M6.2
Honeydew, Whitethorn, Petrolia
17 Aug 1991 · 27 km away · intensity VII
Moderate damage ($1–5M)
- 1975M5.6
Oroville
1 Aug 1975 · 284 km away · intensity VIII
$3 million damage
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.