Fault mechanics and the kinematics of block rotations.

Abstract

In many strike-slip tectonic settings, large rotations (up to 100 o ) of crustal blocks have been inferred from paleomagnetic data. These blocks are bounded by sets of parallel faults, which accommodate the relative motion between the blocks as regional deformation progresses. Simple geometrical considerations require that the faults must also rotate. In this paper we show that on the basis of mechanical considerations, the amount of fault rotation permissible under a stationary stress field is limited to 20o to 45o. Consequently, block rotations >40o or 45o require more than one set of accompanying faults to accommodate the block rotation. Examples of such multiple sets with 40o-45o between them, as predicted by the model, were recognized in Sistan, Iran; in Yerington, the Lake Mead area, Nevada; and in S California.-Authors