KINEMATIC AND DYNAMIC ANALYSIS OF A LOW-ANGLE STRIKE-SLIP-FAULT - THELAKE-CREEK FAULT OF SOUTH-CENTRAL IDAHO

A large, low-angle strike-slip fault with significant offset is presen t in south-central Idaho. The 40+ km long Lake Creek fault is oriented N50 degrees W, 30 degrees SW and has a slip vector 18 km long, plungi ng 2 degrees to N55 degrees W. Slip was determined by restoring the of fset of a map-scale fold trough. Thus, the fault is a dextral-normal f ault with predominant dextral strike-slip and minimal normal dip-slip displacement. The present-day gentle dip of the fault appears to be th e original dip since older folds and coeval to younger dykes in the ar ea are not tilted. Several hypotheses for the origin of the low-angle fault are rested. Field and kinematic data support the interpretation that the fault formed as a low-angle strike-slip fault, not as a react ivated thrust fault nor in association with other regional fault syste ms. Based on fault array analysis and published experimental fault stu dies, the Lake Creek fault is interpreted to have formed as a low-angl e strike-slip fault owing to a nearly axial compressive state of stres s with a subhorizontal ol, and crustal anisotropy induced by NW-trendi ng folds and SW-dipping axial planar cleavage. Copyright (C) 1996 Else vier Science Ltd