Shaking damage at Santa Rosa City Hall caused by the April 1906 San Francisco earthquake (Magnitude 7.9).
Photo from Stienbrugge Collection, National Information Service for Earthquake Enginnering, Pacific Earthquake Engineering Research Center, University of California, Berkeley.
Historic Earthquakes Interactive Map
The Historic Earthquake Online Database is an interactive web map documenting the effects of notable historical California earthquakes, as reported by the people who survived the experience. By selecting an earthquake on the map, you can see where it was felt, and the effects reported at those locations. These “felt reports” are usually from newspapers during the 1850 to 1930 time period. The felt reports were compiled and published in 1981 and 1982 with updates added through the years. Not all earthquakes have intensity maps and felt reports online since the conversion from printed report to web page is an ongoing process. Most of the San Francisco Bay area events between 1838 and 1906 are in the database.
Map Sheet 49: Epicenters and Areas Damaged by M>5 California Earthquakes, 1800-1999
Map Sheet 49 shows epicenters of potentially damaging earthquakes, magnitude 5 or greater, which have occurred in California since 1800. In addition, an inset map shows areas that have been damaged by earthquakes of magnitude 7 or greater, and the minimum number of times such damage has occurred. The map measures 27 inches by 37 inches.
The 200-year earthquake history is divided into three nearly equal time periods, distinguished by red, blue and green on the epicenter map and bar graph, to show the changes in earthquake occurrence and identification with time.
The map shows that since 1800, earthquakes capable of damaging unreinforced buildings have occurred at least six times in each of these regions: Los Angeles to San Fernando, San Francisco Bay to Santa Cruz, and Eureka to Cape Mendocino. The epicenters of 800 magnitude 5 or greater temblors are shown, including some centered offshore of California, as well as bordering regions of Nevada, Oregon and Mexico. A list of earthquakes of magnitude 5.5 and greater, sorted by latitude for easy locating, is included on the map
California Geological Survey seismologists compared old newspaper and other written accounts of earthquake shaking with accounts of the shaking from earthquakes recorded by modern instruments to determine the most likely epicenters and magnitudes of pre-1932 earthquakes. Most of the information about earthquakes that occurred before the 1849 gold rush comes from reports from the 21 missions near the coast from San Diego to Sonoma. Information about earthquakes from 1850 to 1931 is based largely on newspaper reports. Post-1932 data is from the seismological laboratories at Caltech and UC Berkeley, which began to routinely determine the epicenters and magnitudes of earthquakes in Southern and Northern California, respectively, in 1932 and 1942, supplemented by data from the United States Geological Survey starting in the 1970s. As California's population increased and spread across the state, earthquakes began to be reported in new areas — a fact that is reflected in the color-coded map.
The map indicates that California, on the average, has experienced one magnitude 6 or greater earthquake each year since 1850. It also shows that some areas have been relatively quiet seismically in the last 90 years but were very active in the previous 100 years. The relatively quiet areas include the San Andreas system of faults, which includes the San Jacinto and the Hayward-Rodgers Creek faults. Strong earthquakes also have occurred away from major known surface faults, such as near Vacaville in the Sacramento Valley 1892.
California Earthquake Catalogs