IS-23 is a compilation of felt reports for several widely reported earthquakes dating from times before seismological recording instruments. Primary documentation is emphasized; newspapers also checked for time hear events and possible aftershock. 89 pages. Digital PDF download. IS-23D
From the Introduction:
This study was undertaken to discover historical felt reports for earthquakes that have occurred in Colorado. The main goal of the project was the collection of felt reports for five earthquakes which were thought to have occurred on or about September 16, 1880; November 7, 1882; December, 1891; November 15, 1901; and September 8, 1944. The investigation included field trips to local and private historical collections in many towns in northwestern Colorado. Records at city and county offices, businesses, and churches were also evaluated for earthquake data. Historical documents and other sources were checked at state research libraries and repositories, and at regional and national federal archives, including the National Archives in Washington, D.C., the Federal Records Service, Region 8 in the Denver Federal Center, the research library at the Colorado Historical Society, the Western History collection at the Denver Public Library, the State of Colorado Library and Archives, and the University of Colorado Western.
In addition to these five earthquakes, felt reports for 16 other earthquakes were investigated in towns near their previously estimated epicenters. Other studied reports included two explosions and the Denver-Derby earthquakes of 1967. These events were not researched with the same systematic search at every location or as thoroughly as the five primary events listed above.