Information about past historic earthquakes is used to evaluate seismic hazards. We are refining and extending an existing database of information on historic earthquakes in Washington, Oregon, and British Columbia. The database currently includes information on over 500 Cascadia earthquakes between 1793 and 1929. We are working to produce two additional PC databases; one for earthquakes from 1930-1969, and another dealing with the 1872 North Cascades Earthquake and events that may be its aftershocks.

In a previous project, we compiled information on early Cascadia earthquakes. This database catalog is the only comprehensive collection of source material describing the felt effects of historic earthquakes in this region. It currently includes over a dozen catalog-type sources, and about 400 other sources, including newspaper articles, technical reports, weather observer's records, and entries from diaries. Our database allows all of the information that we have searched out and compiled on Cascadia earthquakes (some of it from very obscure sources) to be conveniently shared with other investigators and with the public. The Cascadia database 1793-1929 is available over the World-Wide-Web in MS-ACCESS format.

The current project is a similar database for earthquakes since 1930, and a special data-base of material on the 1872 earthquake. The 1872 North Cascades earthquake is Washington's largest historic earthquake; estimated magnitude 7.4. The location of this earthquake is controversial. Although a large volume of newspaper accounts was collected as part of geological and geophysical studies of a proposed nuclear reactor site, few copies of these materials were circulated, and they are not widely available. Interpretations of the macroseismic accounts are controversial, and several quite different epicenters have been suggested for this earthquake.

During this reporting period, material related to the 1872 North Cascades (M 7.4) and the 1949 Olympia (M 7.1) earthquakes was scanned and proofread. These are the two largest earthquakes known historically in Washington or Oregon, and copious amounts of material are available. We are formatting this information for the World-Wide-Web.

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