A map is presented showing the epicenters of strong earthquakes, the earlier ones being located from field data obtained from the Descriptive catalog of earthquakes of the Pacific Coast of the United States, 1769 to 1928, and the later from instrumental data. Some general conclusions are suggested from the distribution of these epicenters. The seismicity of groups of counties in northern California is rated on an arbitrary scale. The seismicities are presented in the form of a map.
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