The December 21, 1954 earthquake
M6.4Eureka-Arcata, California
A magnitude 6.4 earthquake 9.3 miles deep, centred in Humboldt County. The 33rd strongest in California’s record since 1900, and the strongest within 50 miles since a magnitude 6.5 on June 6, 1932. 1 aftershock of magnitude 2.5 or more followed within 30 days.
The earthquake
- Magnitude
- 6.4
- moment magnitude (mw)
- Depth
- 9.3 mi
- 15.0 km below the surface
- Local time
- Tuesday, December 21, 1954
- 11:56 PST; 19:56 UTC
- In California’s record
- 33rd
- strongest of 97,065 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event iscgem891371 (“The 1954 Eureka-Arcata, California Earthquake”). The USGS event page carries the ShakeMap, felt reports and the official summary.
Aftershocks
Earthquakes of magnitude 2.5 or more within 20 miles of the epicentre in the 30 days after.
1
Aftershocks in 30 days
4.7
Largest aftershock, Dec 30, 1954
0
On the first day
0
In the 7 days before
- The search radius is the surface rupture length expected for an earthquake of this magnitude (Wells and Coppersmith, 1994), at least 20 and at most 600 miles, so a great earthquake's sequence is counted along its whole fault.
- Before the modern seismic networks of the 1970s many small aftershocks went unrecorded, so early sequences read short.
Counties and cities within 50 miles
Distance from the epicentre to each county boundary (zero when inside) and to each city centre.
Counties
- Humboldt CountyCA · inside
- Trinity CountyCA · 15.0 mi
- Siskiyou CountyCA · 34.0 mi
- Del Norte CountyCA · 37.5 mi
Earthquakes around the epicentre
1,596 earthquakes of magnitude 3 or more within 50 miles of this epicentre since 1973.
Earlier earthquakes of magnitude 5 or more within 50 miles, strongest first
- June 6, 1932M6.5
- April 23, 1906M6.4
- September 22, 1952M6.0
- October 28, 1909M6.0
- August 18, 1908M5.8
- August 20, 1927M5.6
- August 20, 1927M5.3
- February 9, 1923M5.0
- September 22, 1930M5.0
- December 11, 1930M5.0
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.