Reviewed by USGS42y ago
M3.5 earthquake off the coast of Northern California
Friday, September 14, 1984, 17:43:41 UTC · 40.455°N, 127.859°W
A magnitude 3.5 earthquake struck off the coast of Northern California on Friday, September 14, 1984, 17:43:41 UTC, at a depth of 10.0 km (shallow).
- Magnitude
- 3.5
- Minor · ml
- Depth
- 10 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 earthquake
In context
How big was it, and why here?
Energy released
3 tons of TNT
That is about 1/5,615 of the Hiroshima bomb. A magnitude 5.0 releases about 178 times more energy.
Tectonic setting
17 km
from the nearest mapped plate boundary, between the Pacific and Juan de Fuca plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
10 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 has not published any M2.5+ earthquake within 50 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 119 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 · 206 km NE of this epicenter
- 7.1The 1923 Humboldt County, California EarthquakeJanuary 22, 1923 · 239 km E of this epicenter
- 6.8123 km W of Ferndale, CaliforniaNovember 25, 1954 · 182 km E of this epicenter
- 6.884 km W of Ferndale, CaliforniaFebruary 9, 1941 · 220 km E of this epicenter
- 6.8off the coast of Northern CaliforniaJuly 6, 1934 · 206 km NE of this epicenter
- 6.7217 km W of Ferndale, CaliforniaSeptember 10, 1984 · 87 km E of this epicenter
- 6.552 km WNW of Big Lagoon, CaliforniaJuly 15, 1918 · 281 km E of this epicenter
- 6.5235 km W of Port Orford, OregonAugust 5, 1910 · 260 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 4 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1865
Fort Humboldt, Eureka
1 Oct 1865 · 289 km away · intensity IX
Moderate damage ($1–5M)
- 1922M7.6
Northern
31 Jan 1922 · 208 km away
Limited damage (under $1M)
- 1923M7.1
Northern
22 Jan 1923 · 239 km away · intensity VIII
Limited damage (under $1M)tsunami
- 1941M6.6
Northern
9 Feb 1941 · 221 km away · intensity VI
Limited damage (under $1M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.