A documentary study of the felt effects of the great California earthquake of 1857
We have collected over 60 hitherto unpublished accounts of the California earthquake of January 9, 1857. We have used them, together with those already known, to estimate felt intensities and prepare an isoseismal map which roughly indicates the level of short-period ground motion experienced during this earthquake. Modified Mercalli intensities of VI to VII occurred in the modern metropolitan areas of southern California, and VI to VIII in the southern San Joaquin Valley. The intensity along the fault was IX or more. Instances of seiching, fissuring, sandblows, and hydrologic changes were reported from Sacramento to the Colorado River delta. Most reports say that shaking lasted between one and three minutes. At least two large aftershocks occurred within a week of the main event.
Additional Information© 1978 Seismological Society of America. Manuscript received June 9, 1978. We owe particular thanks to Dan Burd, who searched through a great number of possible sources in order to find many of those that we have used here. Many historians and librarians have helped us in our search for information. We gratefully acknowledge the help of W. Harland Boyd, Lori Davisson, the late Maynard Geiger O.F.M., Roberta Nichols, Virginia Rust, Marilyn Seifert, Helen Uliberry, Richard S. Whitehead, and members of the staffs of the Bancroft Library, the California State Library, the Historical Department of the Church of Jesus Christ of Latter-Day Saints, the National Archives, the Periodical Division of the Library of Congress, and the Serra Museum Library. Laurie Sieh, Carlos Salvado, Alejandro Nava, and George E. Agnew helped produce our translations from the Spanish. We offer special thanks to Clarence Allen and Rodman W. Paul, who provided the encouragement to begin this project. This work has been supported with funds provided by the California Institute of Technology (Division of Geological and Planetary Sciences), U.S. Geological Survey Contracts 14-08-0001-15225 and 14-08-0001-16774, NASA Grant NGR 05-009-246, and Mr. and Mrs. George E. Agnew.
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