M3.8 earthquake 73 km WSW of Ferndale, California

Thursday, December 8, 2005, 09:47:08 UTC · 40.372°N, 125.088°W

A magnitude 3.8 earthquake struck 73 km WSW of Ferndale, California on Thursday, December 8, 2005, 09:47:08 UTC, at a depth of 8.1 km (shallow). USGS received 22 “Did You Feel It?” reports, with a maximum reported intensity of IV (light).

Magnitude: 3.8; Minor · md
Depth: 8 km; Shallow
Felt reports: 22; Max intensity IV
Est. shaking: I; Not felt (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

7 tons of TNT

That is about 1/2,062 of the Hiroshima bomb. A magnitude 5.0 releases about 65 times more energy.

Tectonic setting

5 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

8 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

Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.

Place	Intensity	Reports	Distance
95540<br>0.302	II · Weak	4	85 km
95536<br>0.311	II · Weak	3	72 km
95503<br>0.320	III · Weak	2	92 km
95501<br>0.320	II · Weak	2	92 km
95006<br>0.320	I · Not felt	2	437 km
95558<br>0.330	IV · Light	1	74 km
95521<br>0.330	II · Weak	1	104 km
94515<br>0.330	II · Weak	1	290 km
93451<br>0.330	I · Not felt	1	641 km
95547<br>0.330	I · Not felt	1	87 km

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 M4.6 on December 23, 2005. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 188 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 18 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 · 295 km away · intensity VIII
1 death$8 million damage
1954M6.6
Humboldt County
21 Dec 1954 · 114 km away
1 death$2 million damage
1932M6.5
Eureka
6 Jun 1932 · 78 km away · intensity VIII
1 deathModerate damage ($1–5M)
1992M7.1
Humboldt County: Ferndale, Petrolia
25 Apr 1992 · 65 km away · intensity VIII
$75 million damagetsunami
1980M7.2
North Coast
8 Nov 1980 · 109 km away · intensity VII
$2 million damage
1991M6.2
Honeydew, Whitethorn, Petrolia
17 Aug 1991 · 65 km away · intensity VII
Moderate damage ($1–5M)

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers