Faults with asymmetric damage zones in sandstone, Valley of Fire State Park, southern Nevada

Models for the evolution of faults formed by shearing along joint zones in Aztec sandstone, Valley of Fire, Nevada predict damage zones either localized within the fault core or symmetrically distributed about the core or a slip surface therein. We expand these models by presenting two examples of faults with asymmetric damage zones from the same field locality. Asymmetric damage is attributed to the inherited geometry of a parent joint with a peripheral joint breakdown fringe. One example is of a fault formed along a parent joint with continuous breakdown fringe. The other example is of a fault formed in part along a parent joint with abrupt breakdown fringe. When compared with the symmetric examples, the damage in the asymmetric cases is minimized due to the presence of an already through-going surface. (C) 2004 Elsevier Ltd. All rights reserved.