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Revisiting the M6.5 21 December 1954 Korbel Earthquake

The December 21, 1954 M6.5 earthquake near Korbel, CA, in Humboldt County remains one of the more interesting North Coast historic events. The felt area extended from north of Coos Bay, OR, to south of Santa Rosa and Sacramento, CA, and eastward past Alturas, CA. Nearby residents considered it the strongest quake since 1906 and fishermen described flow on the Mad River reversing course. It is the only large historic earthquake in the region that may have been located on a surface fault within the overlying North American plate. It was recorded on two nearby accelerometers of the Coast and Geodetic Survey, on stations of the seismographic networks of UC Berkeley and the California Seismological Lab in Pasadena, CA and at regional and teleseismic sites. A variety of investigations between 1954 and the 1980s have produced at least 14 locations clustered between 40.78°N and 124.87°W in the SW and 40.94°N and 124.0°W in the NE. The estimated epicenters are based on analyses of arrival and t_S-t_P times, polarization and/or felt reports. Using data published in various reports and papers, as well as unpublished data from Berkeley’s archives, including original recordings, we redetermine the earthquake’s hypocenter and evaluate the uncertainties in the estimation. We review the magnitude and estimate a mechanism, in addition to comparing the 1954 event and its aftershocks with event information and data available in the modern catalog and archives.

Session: Characteristics, Hazards and Evolution of the Gorda Region of the Cascadia Subduction Zone [Poster]

Type: Poster

Room: Evergreen Ballroom

Date: 4/21/2022

Presentation Time: 08:00 AM Pacific

Presenting Author: Margaret Hellweg

Student Presenter: No

Additional Authors