One of the strongest shocks to affect the Denver area in the 1960's occurred on August 9, 1967.
An isoseismal map for this event is shown in the images below. Felt reports and intensity ratings were described by von Hake and Cloud (1969)
Intensity VII damage was reported in Northglenn, where plate glass windows broke, many walls, ceilings, foundations, and concrete floors cracked, and several businesses sustained damage due to fallen merchandise. A liquor store estimated damage at $10,000 to $20,000.
Intensity VI damage was reported in 28 locations, many of which suffered considerable cracked plaster and mortar, broken windows, damaged foundations and chimneys, and damage to household goods. The earthquake was felt as far as Sterling, Pueblo, and Laramie.
Based on the isoseismal map below, we estimate the felt area to be about 50,000 sq km. Von Hake and Cloud (1969)
proposed a size of 39,000 sq km, while Hadsell (1968)
indicated it was felt over 117,000 sq km. Docekal (1970)
reported a felt area of 52,000 sq km. A magnitude of mb 5.3 was reported for this earthquake by von Hake and Cloud (1969)
. Nuttli and others (1979)
calculated an mb of 4.9 and Ms of 4.4. Herrmann and others (1981)
suggested a focal depth of 3 km for this event. The overall felt area is prominently elongated in directions parallel and perpendicular to the mountain front. The intensity V and VI contours also are oriented in an elongate pattern perpendicular to the mountain front.
References:Colorado Geological Survey - Earthquake Reference Collection - Denver - August 9, 1967 Colorado Geological Survey - Visit us on Facebook