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The December 20, 1940 earthquake

M6.0near Shelter Cove, California

A magnitude 6.0 earthquake 9.3 miles deep, 27.0 miles off Humboldt County. The 86th strongest in California’s record since 1900, and the strongest within 50 miles since a magnitude 6.0 on March 18, 1910.

The earthquake

Magnitude
6.0
moment magnitude (mw)
Depth
9.3 mi
15.0 km below the surface
Local time
Friday, December 20, 1940
15:40 PST; 23:40 UTC
Epicentre
39.73°N, 124.42°W
27.0 mi from Humboldt County
In California’s record
86th
strongest of 97,065 since 1900
Within 50 miles
3
counties; more on this date

USGS ANSS Comprehensive Earthquake Catalog, event iscgem901741 (“44 km SW of Shelter Cove, California”). The USGS event page carries the ShakeMap, felt reports and the official summary.

Counties and cities within 50 miles

Distance from the epicentre to each county boundary (zero when inside) and to each city centre.

Counties

Earthquakes around the epicentre

1,344 earthquakes of magnitude 3 or more within 50 miles of this epicentre since 1973.

Earthquakes of magnitude 3 or more within 50 miles of the epicentre, by year 1973: 4 1974: 13 1975: 16 1976: 21 1977: 22 1978: 27 1979: 31 1980: 32 1981: 67 1982: 19 1983: 47 1984: 17 1985: 27 1986: 49 1987: 63 1988: 23 1989: 19 1990: 28 1991: 45 1992: 256 256 1993: 37 1994: 36 1995: 21 1996: 12 1997: 14 1998: 14 1999: 12 2000: 14 2001: 14 2002: 24 2003: 13 2004: 13 2005: 13 2006: 15 2007: 8 2008: 7 2009: 4 2010: 8 2011: 4 2012: 9 2013: 12 2014: 12 2015: 10 2016: 8 2017: 12 2018: 4 2019: 24 2020: 14 2021: 32 2022: 9 2023: 7 2024: 64 2025: 18 19731978198319881993199820032008201320182023

Earlier earthquakes of magnitude 5 or more within 50 miles, strongest first

USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.