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CATALOG OF SANTA BARBARA EARTHQUAKES - 1800 TO 1960 compiled and edited by Arthur Gibbs Sylvester, 2001 INTRODUCTION The purpose of this catalog is to document the times, sizes, and felt effects of pre-instrumental earthquakes that have been felt in the Santa Barbara and Ventura area, as well as to ascertain the nature and location of damage, if any, resulting from a given earthquake of a given intensity or magnitude. Four seismographs were installed by Caltech by 1925, and a broader southern California network was established in 1932 to locate small earthquakes. Even then, the Santa Barbara area was on the edge of the network, and the azimuthal distribution of seismographs was not optimal for locating earthquakes with a precision of better than about 10 km. Not until 1969 was a network of seismographs installed around the Channel by the U.S. Geological Survey for the specific purpose of locating earthquakes there. We gathered information initially about Santa Barbara earthquakes from the catalog of Townley and Allen (1939). Then we read the Santa Barbara newspapers from their first editions in 1852 to 1960. Once a fairly extensive listing had been compiled from these two sources, we selectively read newspapers from Oxnard, Ventura, Ojai, Santa Paula, Lompoc, Santa Maria, and Carpinteria to get a better idea of the location of any given earthquake and the regional extent of its felt area. Newspapers from these cities were read for the period three days before and six days after a given earthquake in the primary Santa Barbara listing. We also read the same newspapers for the same period of time around major earthquakes that occurred outside of the study area, such as the 1933 Long Beach earthquake, to determine what effects, if any, were recorded in Santa Barbara. We sought additional information in diaries in the local libraries and historical societies with no success owing to the paucity of extant diaries. Subsequently we checked and updated our information for the large earthquakes using statewide catalogs prepared by Toppozada et al. (1981), Coffman, et al. (1982), and Ellsworth (1990). The areal distribution of data is too limited to permit exact locations of most earthquakes or to draw isoseismal maps for any but the largest earthquakes. Thus data are available from only a few towns, most of which did not have newspapers until the early 1900's, scattered along the coast. Santa Barbara, located as it is between the sea to the south and the mountains to the north - and only scattered ranches to the west and east, is, in effect, only one datum for any given earthquake. Many earthquakes take place in the Santa Barbara Channel, and their epicenters cannot be located with any confidence whatsoever from the data available before 1932. The readings were done by Nancy Riggs, Leslie Frambrini, David Hoexter, and Arthur Sylvester. Tracy Hoganson transcribed the typewritten notes into word processed text. PRINCIPAL EARTHQUAKES The Santa Barbara area has been affected by three major earthquakes and several lesser ones during the time covered by the catalog: 1812, 1925, and 1927. The earthquake of 1812 is regarded as one of the largest earthquakes in California history, based evidently on the size of the felt area, the extensive destruction to missions in Santa Barbara County, and the report of seismic sea waves. The assigned magnitude of this earthquake is 7.0 (Toppozada et al., 1981; Evernden and Thompson, 1985). The data for this earthquake are meager unfortunately, and permissive arguments can be presented which not only raise doubts about the existence of any seismic sea waves (Grauzinis, et al., 1965), but also downgrade the probable magnitude and scope of the earthquake (Sylvester, 1978). The great Fort Tejon earthquake of 1857 (M 8), which accompanied the rupture of the San Andreas fault for a distance of about 300 km from Parkfield to Cajon Pass, was "sensibly felt" in Santa Barbara but did not cause significant damage according to fairly extensive and detailed press reports. The effects were considerably stronger in the Santa Clara River valley and were described in detail in the Santa Barbara newspapers. The earthquake of 29 June 1925 (M 6.3) was Santa Barbara's most destructive earthquake in terms of loss of life and property. Indeed, the property damage was so extensive, that much of the downtown part of the city had to be rebuilt, and was rebuilt according to the dictates of an architectural plan adopted by the City only weeks after the earthquake, resulting in the attractive Spanish style that characterizes the City today. Thus the earthquake forced one of the first urban renewal projects in California. More significantly, the Santa Barbara earthquake exposed inadequacies of contemporary building design and construction, prompting much discussion and little remedial legislative action statewide until the general lessons learned were confirmed by the 1933 Long Beach earthquake. The heavy damage to public schools in Long Beach, coupled with the realization of the enormous loss of life that might have occurred if the earthquake had taken place only an hour or so earlier, led to the formulation and enactment of the Field Act in 1993 by the State Legislature. That act gave jurisdiction to the State Division of Architecture to regulate the design and construction of public school facilities. Significant expansion of the codes to cover other kinds of public buildings, such as hospitals, fire and police stations, did not happen until after the 1971 San Fernando earthquake. The 1927 Pt. Arguello earthquake (Byerly, 1930), Ms and Mw = 7.0; Mo=3 x 1026 ( Helmberger et al. 1992; Satake and Somerville, 1992), generated the only truly documented seismic sea waves by a local earthquake (Satake and Somerville, 1992). The epicenter was about 45 km due west of Pt. Conception (Helmberger et al., 1992). The earthquake damaged nearby coastal cities of Lompoc and Santa Maria. Other noteworthy earthquakes that strongly affected Santa Barbara and vicinity include the Los Alamos earthquakes of 1902 and 1915, and the Santa Barbara earthquake of 1941. The strongest intensities in both the 1902 and 1915 earthquakes were clearly centered in the Los Alamos area, and their location, together with numerous reports of small earthquakes before and since in the same area, indicate that the central part of the Santa Maria basin is a zone of active faulting at depth (Sylvester and Darrow, 1979). The earthquake of 1941 (M 5.9) was centered in the Santa Barbara Channel about 10 km south of the City of Santa Barbara and caused much window breakage and cracking of walls in the downtown part of the City where the damage was so extensive in 1925. Reports of earthquakes emanate from Ojai during the period of the catalog as well as from Ventura and nearby areas. The Ventura reports probably reflect activity offshore of Pt. Mugu. This judgment is based on the similarity of felt reports of numerous earthquakes believed to have been generated in that area with felt reports from the 1973 Pt. Mugu earthquake (M 5.3). All times given in this catalog are local times.
EARTHQUAKE SWARMS Reports of several small earthquakes clustered closely in time are found in Townley and Allen (1939) and various newspaper stories for the years 1815, 1854, 1909, 1920, and 1929. Sylvester et al (1970, their table I) concluded that these temporally and evidently areally clustered earthquakes represented swarm activity, similar to that of the 1968 Santa Barbara Channel earthquake swarm. The epicentral data provided by the Caltech network since 1932 indicate that the seismic activity of the eastern and central Santa Barbara Channel is characterized by swarms, relatively frequent minor earthquakes, and infrequent major earthquakes, including those of 1812, 1925, 1941, 1968 (Sylvester et al., 1970) and possibly that in 1978. ABBREVIATIONS For convenience, the following abbreviations are used through the text:
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