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- 16 - <br />The 1960 Montrose earthquake and other small nearby earthquakes appear <br />to be associated with the northeastern flank of the Uncompahgre <br />Plateau. An analysis based on earthquake magnitude and distance from <br />the JD-5 lease indicate that the historic earthquakes probably <br />produced intensities of V or less at the lease. <br />The Uncompahgre Plateau is 'a positive structural block bounded by <br />monoclinal folds and faults on both its northeast and southwest sides. <br />Cater (1970) describes geomorphic evidence which indicates that the <br />structural block and bounding faults were probably tectonically active <br />during Pliocene and Quaternary time. About 1,300 feet of post- Kansan <br />uplift is indicated in the vicinity of Unaweep Canyon, Kirkham and <br />Rogers (1978). Kirkham and Rogers (1978) have mapped several fault <br />zones, of late Cenozoic age, along the flanks of the Uncompahgre <br />Plateau. Two small faults, one on the northeast flank and the other <br />on the southwest flank of the plateau, show evidence of Quaternary <br />movement. The other faults along the uplift may have moved during <br />Quaternary time; however, detailed studies would be required to <br />establish if Quaternary movement has occurred on all the faults. <br />Post - Triassic displacement on the faults bordering the Ute Creek <br />graben on the southwest flank of the plateau has amounted to about 800 <br />to 1,200 feet. <br />The complex fault zones flanking the Paradox Valley have resulted <br />primarily from the collapse of the anticline's crest as a result of <br />salt solution and flowage. These faults are apparently relatively <br />shallow features whidz terminate in the salt core of the anticline. <br />Considering the existing potential for salt flowage related to <br />