Faulted joints: kinematics, displacement-length scaling relations and criteria for their identification

Structural geometries and kinematics based on two sets of joints, pinnate: joints and fault striations, reveal that some mesoscale faults at Split Mou ntain, Utah, originated as joints. Unlike many other types of faults. displ acements (D) across faulted joints do nor scale with lengths (L) and theref ore do not adhere to published fault scaling laws. Rather, fault size corre sponds initially to original joint length. which in turn is controlled by b ed thickness for bed-confined joints. Although Faulted joints will grow in length with increasing slip, the total change in length is negligible compa red to the original length, leading to an independence of D from L during e arly stages of joint reactivation. Therefore, attempts to predict fault len gth, gouge thickness, or hydrologic properties based solely upon D-L scalin g laws could yield misleading results for faulted joints. Pinnate joints. d istinguishable from wing cracks, developed within the dilational quadrants along faulted joints and help to constrain the kinematics of joint reactiva tion. (C) 2001 Elsevier Science Ltd. All rights reserved.