Patterns in the development of extensional fault-block shapes from comparison of outcrop-scale faults and experimental physical models

The geometry and kinematics of normal fault blocks and subsidiary faults within fault blocks are illustrated by centimeter- to meter-scale faults in an exposure of Tertiary sedimentary rocks in Arizona and are interpreted using results from previously published physical models. In map view, the outcrop fault population consists of anastomosing curved and planar faults. In cross-section there are planar faults and curved faults with either smooth or abrupt (ramp-flat) curvature. The fault patterns resemble those of physical models and larger faults in other extended terrains. Ramp-flat faults with planar and curved faults and tilt-block domains are the most prominent structures. Ramp-flat geometry prevails where faults intersect bedding at low angles. Internal deformation of rollover structures due to both accommodation and extension of the upper plate was accomplished mainly by slip on arrays of smaller faults in synthetic tilt-block arrays and by crisscrossing horst-and-graben-bounding faults. -from Authors