Fault and joint geometry at Raft River geothermal area, Idaho ( USA).

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 E at <50 on top of metamorphosed Precambrian and Lower Palaeozoic rocks. The major set of faults occur as conjugate pairs that are bisected by vertical extension fractures. The second set of faults 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.-from STAR, 20(12), 1982