Fault and joint geometry at Raft River geothermal area, Idaho

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Report: Fault and joint geometry at Raft River geothermal area, Idaho

Raft River geothermal reservoir is formed by fractures in sedimentary strata of the Miocene and Pliocene Salt Lake Formation. The fracturing is most intense at the base of the Salt Lake Formation, along a decollement that dips eastward at less than 5 0 on top of metamorphosed Precambrian and Lower Paleozoic rocks. Core taken from less than 200 m above the decollement contains two sets of normal faults. The major set of faults dips between 50 0 and 70 0. These faults occur as conjugate pairs that are bisected by vertical extension fractures. The second set of faults dips 10 0 to 20 0 and may parallel part of the basal decollement or reflect the presence of listric normal faults in the upper plate. Surface joints form two suborthogonal sets that dip vertically. East-northeast-striking joints are most frequent on the limbs of the Jim Sage anticline, a large fold that is associated with the geothermal field. The north-trending joint set is prominent in the fold's hinge. Surface joint intensity decreases in proximity to known faults, indicating that surface joint intensity mapping may be useful for locating the surface traces of faults in the reservoir.

Guth, L. R.; Bruhn, R. L.; Beck and S. L.  

DOE Information Bridge, 7/1/1981



Guth, L. R.; Bruhn, R. L.; Beck, S. L.  . 7/1/1981. Fault and joint geometry at Raft River geothermal area, Idaho. (!) : DOE Information Bridge.

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