1954 Eureka earthquake

1954 Eureka earthquake
1954 Eureka earthquake is located in California
1954 Eureka earthquake
UTC time1954-12-21 19:56:29
ISC event891371
USGS-ANSSComCat
Local dateDecember 21, 1954 (1954-12-21)
Local time11:56 am Pacific Time
Magnitude6.5 Mw
Epicenter40°47′N 123°52′W / 40.78°N 123.87°W / 40.78; -123.87
TypeUnknown
Areas affectedNorth Coast (California)
United States
Total damage$2 million
Max. intensityMMI VII (Very strong)
Casualties1 death, 50 injuries

The 1954 Eureka earthquake occurred at 11:56 am on December 21, just east of Eureka and Arcata, California in the United States. The unknown type shock had a moment magnitude of 6.5 and a maximum Mercalli intensity of VII (Very strong). Buildings swayed, windows were broken, and the Humboldt County Courthouse collapsed. A total of US$2 million damages was counted, with one death and 50 injuries.

Geology

See also: Geology and geological history of California

The earthquake was located within the Franciscan subduction complex, taking up northwestern California.[1] The history of the subduction complex spans for about 150 million years, with significant events happening in this time period.[2][3] Regularly, faults are hidden beneath the ocean, but at this particular subduction complex, the faults can be spotted piercing through land. The faults are considered active, with evidence of rupture originating within the last 10,000 years.[4]

Earthquake

The earthquake struck Eureka, Arcata, and the surrounding Humboldt County on December 21, 1954, at approximately 11:56 am. The earthquake had a magnitude of 6.5 Mw  with an unknown depth.[5] There have been an estimated 10 attempts to locate the earthquake. Contributing to this problem was the reduction of operating seismic stations within Humboldt County, with a total of two seismic stations. Other nearby seismic stations also recorded the earthquake, though these attempts were not that useful. For the earthquake, a total of two radio signals were sent, which helped identify the time of the earthquake.[4]

Damage

In local areas, chimneys toppled, windows shattered, and ancient buildings swayed dangerously.[6] The earthquake caused the Humboldt County courthouse to be deemed uninhabitable, prompting reconstruction of the building.[7] The Sweasey Dam broke, threatening nearby areas. In addition, a 65,000 U.S. gal (250,000 L) water tank fell, located near Fortuna, California.[6]

Aftermath

Soldiers of the United States Armed Forces inspected some harbors of the Humboldt County for damage. Damage was found in the jetties, prompting repair money costing US$300,000.[8] A total of US$2 million damages was counted, with one death and 50 injuries.[6]

References

  1. ^ Dumitru, Trevor A.; Ernst, W.G.; Hourigan, Jeremy K.; McLaughlin, Robert J. (2015-06-11). "Detrital zircon U–Pb reconnaissance of the Franciscan subduction complex in northwestern California". International Geology Review. 57 (5–8): 767–800. doi:10.1080/00206814.2015.1008060. ISSN 0020-6814.
  2. ^ Wakabayashi, John (2015-02-03). "Anatomy of a subduction complex: architecture of the Franciscan Complex, California, at multiple length and time scales". International Geology Review. 57 (5–8): 669–746. doi:10.1080/00206814.2014.998728. ISSN 0020-6814.
  3. ^ Rutte, Daniel; Garber, Joshua; Kylander-Clark, Andrew; Renne, Paul (2021-03-04), An Exhumation Pulse From the Nascent Franciscan Subduction Zone (California, USA), doi:10.5194/egusphere-egu21-12967
  4. ^ a b Dengler, Lori (27 July 2024). "Not My Fault: An earthquake enigma: Where was the 1954 earthquake located?" (PDF). Times-Standard – via Humboldt County.
  5. ^ "M 6.5 – The 1954 Eureka-Arcata, California Earthquake". United States Geological Survey. Retrieved 2024-10-08.
  6. ^ a b c "THROWBACK THURSDAY: Remembering the Dec. 21, 1954 earthquake". Times-Standard. 2017-12-21. Retrieved 2024-10-08.
  7. ^ "Court House Plans Approved by Board". Blue Lake Advocate. April 25, 1957 – via University of California, Riverside.
  8. ^ "$300,000 Jetty Repairs Scheduled for Spring". Blue Lake Advocate. March 7, 1957 – via University of California, Riverside.

Further reading

  • Steinbrugge, Karl V.; Moran, Donald F. (1957). "An Engineering Study Of The Eureka, California, Earthquake Of December 21, 1954". Bulletin of the Seismological Society of America. 47 (2): 129–153. doi:10.1785/BSSA0470020129. ISSN 1943-3573.