M2.8 earthquake 73 km WNW of Ferndale, California

Wednesday, May 27, 1981, 09:49:55 UTC · 40.740°N, 125.108°W

A magnitude 2.8 earthquake struck 73 km WNW of Ferndale, California on Wednesday, May 27, 1981, 09:49:55 UTC, at a depth of 14.4 km (shallow).

Magnitude: 2.8; Minor · md
Depth: 14 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

231 kg of TNT

That is about 1/65,214 of the Hiroshima bomb. A magnitude 5.0 releases about 2,065 times more energy.

Tectonic setting

14 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

14 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 8 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M4.0 on June 23, 1981. 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 134 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 12 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 · 103 km away
1 death$2 million damage
1932M6.5
Eureka
6 Jun 1932 · 69 km away · intensity VIII
1 deathModerate damage ($1–5M)
1980M7.2
North Coast
8 Nov 1980 · 83 km away · intensity VII
$2 million damage
1865
Fort Humboldt, Eureka
1 Oct 1865 · 59 km away · intensity IX
Moderate damage ($1–5M)
1922M7.6
Northern
31 Jan 1922 · 44 km away
Limited damage (under $1M)
1923M7.1
Northern
22 Jan 1923 · 29 km away · intensity VIII
Limited damage (under $1M)tsunami

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

Nearby trackers