The Carbondale, Colorado, earthquake swarm of April - May, 1984

Abstract

During the Carbondale, Colorado, earthquake swarm (Mi <3.2) of April -May 1984, a total of 34 earthquakes were located using regional data or local data from a temporary network installed in the epicentral area. These earthquakes were relocated with the method of Joint Hypocenter Determination (JHD) in order to better delineate the source zone of the swarm. The majority of the earthquakes occurred about 7 km south-southwest of Carbondale, at the northern terminus of the Elk Mountain anticline. The most precisely determined hypocenters of the swarm have focal depths in the 2 to 7 km range. Two composite focal mechanisms were constructed from local first-motion data. One of these mechanisms corresponds to normal faulting and the second suggests reverse faulting.

Can flexural-slip faults related to evaporite dissolution generate hazardous earthquakes? The case of the Grand Hogback monocline of west-central Colorado

“…The seismic activity recorded in the area tends to be spatially associated with the Grand Hogback monocline, and it may be partially related to active evaporite tectonism (Kirkham and Rogers, 1981;Goter et al, 1988;Unruh et al, 1993;Morgan et al, 2012). However, none of the historically or instrumentally recorded earthquakes are known to have produced surface ruptures, suggesting that the faulting events identifi ed in the trenches may be related to earthquakes larger than the bigger events of the historical earthquake catalogue (I = V, M = 4.3).…”

“…The swarm prompted the U.S. Geological Survey to establish a temporary, portable microseismic network two days after the 14 May earthquake (Goter et al, 1988). An additional 17 well-located earthquakes with duration magnitudes of 1.3-2.6 were recorded by their microseismic network during the remaining days of May.…”

Seismicity of the rocky mountains and Rio Grande Rift from the EarthScope Transportable Array and CREST temporary seismic networks, 2008–2010

“…The Colorado Geological Survey has in the past published volumes of seismicity, fault activity observations, and historical felt reports in Colorado [ Kirkham and Rogers, , , ]. Tectonic earthquakes in Colorado are interpreted to occur along reactivated Laramide and older structures, at sites of evaporite deformation [ Bass and Northrop , ; Mallory , ; Goter et al ., ; Kirkham , ], and near Quaternary faults, but little seismicity is attributed to the Rio Grande Rift [ Kirkham and Rogers , ; Bott and Wong , ; Kirkham and Rogers , , ; Kirkham and Scott , ; Bott et al, ].…”