Reviewed by USGSOregon35y ago
M2.6 earthquake 110 km WSW of Brookings, Oregon
Saturday, August 31, 1991, 15:01:48 UTC · 41.785°N, 125.567°W
A magnitude 2.6 earthquake struck 110 km WSW of Brookings, Oregon on Saturday, August 31, 1991, 15:01:48 UTC, at a depth of 3.9 km (shallow).
- Magnitude
- 2.6
- Minor · ma
- Depth
- 4 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
112 kg of TNT
That is about 1/134,692 of the Hiroshima bomb. A magnitude 5.0 releases about 4,266 times more energy.
Tectonic setting
23 km
from the nearest mapped plate boundary, between the Juan de Fuca and North American plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
4 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 5 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M2.9 on August 31, 1991. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 2.8108 km WSW of Brookings, Oregon35y ago · 4 km N of this epicenter
- 2.8134 km WSW of Pistol River, Oregon35y ago · 34 km NW of this epicenter
- 2.873 km WSW of Brookings, Oregon35y ago · 37 km E of this epicenter
- 2.6116 km WSW of Pistol River, Oregon35y ago · 16 km NW of this epicenter
- 2.9145 km W of Crescent City, California35y ago · 37 km SW of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 200 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 · 66 km S of this epicenter
- 7.2The 1980 Eureka, California EarthquakeNovember 8, 1980 · 132 km SE of this epicenter
- 7.1The 1923 Humboldt County, California EarthquakeJanuary 22, 1923 · 152 km S of this epicenter
- 7.0136 km WSW of Brookings, OregonAugust 17, 1991 · 27 km SW of this epicenter
- 6.9103 km W of Pistol River, OregonJuly 13, 1991 · 45 km N of this epicenter
- 6.8123 km W of Ferndale, CaliforniaNovember 25, 1954 · 149 km S of this epicenter
- 6.884 km W of Ferndale, CaliforniaFebruary 9, 1941 · 129 km S of this epicenter
- 6.8off the coast of Northern CaliforniaJuly 6, 1934 · 71 km S of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 11 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 2 recorded deaths. The most severe:
- 1954M6.6
Humboldt County
21 Dec 1954 · 174 km away
1 death$2 million damage
- 1932M6.5
Eureka
6 Jun 1932 · 159 km away · intensity VIII
1 deathModerate damage ($1–5M)
- 1980M7.2
North Coast
8 Nov 1980 · 132 km away · intensity VII
$2 million damage
- 1991M6.2
Honeydew, Whitethorn, Petrolia
17 Aug 1991 · 200 km away · intensity VII
Moderate damage ($1–5M)
- 1865
Fort Humboldt, Eureka
1 Oct 1865 · 125 km away · intensity IX
Moderate damage ($1–5M)
- 1922M7.6
Northern
31 Jan 1922 · 87 km away
Limited damage (under $1M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.