MONTROSE/RIDGWAY
Earthquake ID:  92 Date: 10/11/1960
Intensity:  VI
Time: 8:05 AM
Magnitude:  5.5
Earthquake Depth: 12  (kM)
Magnitude USGS:  5.5 BRK-3
Latitude: 38.29
Magnitude Other:   Longitude: -107.7
 
Earthquake Information:
In the early morning hours on October 11, 1960 (local time) a large part of southwestern Colorado was shaken by one of the largest earthquakes to occur historically in the state. Tally and Cloud (1962) described the effects of the tremor. Intensity VI damage was reported in Cimarron, Lake City, Montrose, Ophir, Ouray, Placerville, Powderhorn, Ridgway, and Tellu-ride. Plaster, chimneys, and windows were cracked in many of these locations. Perhaps the hardest hit was Montrose, where a foundation was cracked in three places. Numerous other locations reported the earthquake effects at lesser intensity. Grand Junction experienced somewhat high intensities for its distance to the epicenter. Talley and Cloud (1962) reported a magnitude of mb 5.5 for this earthquake. Their isoseismal map for the event indicates the quake was felt over an area of about 26,000 km 2. The isoseismal map shown in Figure 18 was prepared from information in Talley and Cloud (1959), the USCGS quarterly series “Abstracts of Earthquake Reports”, and the NOAA intensity file computer printout. The felt area is somewhat larger on Figure 18, being approximately 39,000 km 2. Unruh and others (1993) relocated this event and report a slightly different epicentral location; we use their location in Table 1.
 
Location Map: (click on image for full size view)
Location Map for Earthquake ID 92
 
References:
31 - Coffman, J.L., von Hake, C.A., and Stover, C.W., 1982, Earthquake History of the United States: U.S. National Oceanic and Atmospheric Administration and U.S. Geological Survey, Publication 41-1 (through 1980), 258 p.
112 - Stover, C.W., Reagor, B.G., and Algermissen, S.T., 1984, Seismicity map of the State of Colorado: U.S. Geological Survey Miscellaneous Field Studies Map MF-1694.
118 - Talley, H.C., and Cloud, W.K., 1962, United States earthquakes 1960: U.S. Coast and Geodetic Survey, 90 p.
125 - Unruh, J.R., Wong, I.G., Bott, J.D.J., Silva, W.J., and Lettis, W.R., 1993, Seismotectonic evaluation, Rifle Gap Dam, Silt Project, Ruedi Dam, Fryingpan-Arkansas Project, northwestern Colorado: unpublished report prepared by William Lettis & Associates and Woodward-Clyde Consultants for U.S. Bureau of Reclamation, Denver, Colorado, 154 p.
137 - Wong, I.G., 1991, The 1986 Crested Butte, Colorado earthquake swarm: The Mountain Geologist, v. 28, no. 1, p. 3-8.