Lateral displacement variation and lateral tip geometry of normal faults in the Canyonlands National Park, Utah

The along-strike displacement variation of 20 well-exposed normal faults from the Canyonlands, Utah, is described and analysed. The displacement profiles of these faults are highly variable, and most irregularities can be related to fault segmentation. Many of the profiles are highly asymmetric, and this can be related to mechanical interaction in some cases. Linear displacement tapers are observed towards all the lateral tips, but the percentage of trace length over which this linear taper occurs is highly variable. Three distinct lateral tip geometries are recognised, referred to informally as types A, B and C. Type A tips have a simple Mode III displacement geometry, Type B tips are characterised by a zone of extensional 'fissures' surrounding the fault tip, and Type C tips are characterised by the development of a monocline beyond the tip. Lateral displacement variation towards tips was analysed by measuring displacement gradients from systematic positions along the fault trace. Lateral displacement gradients measured for 39 tips exhibit a wide range of values (0.016-0.25). Fourteen of these lateral tips are regarded as 'active' since they exhibit signs of recent surface rupturing. These active tips have a similar range of lateral displacement gradients (0.019-0.25) to the overall population. Lateral displacement gradients were correlated with fault parameters such as length, length/maximum displacement (for faults and segments), and proximity to adjacent faults. No positive correlations were found. We suggest that the large range of lateral displacement gradients is mainly due to interactions between neighbouring faults. Additional complexities are likely to have resulted from strength heterogeneities related to jointing, from local variations in remote loading stresses and the frictional properties of the fault surfaces, and from processes related to segment linkage. (C) 1998 Elsevier Science Ltd.