FAULT PATTERNS ON THE OUTER WALL OF THE PERU-CHILE TRENCH

Faults on the outer wall of the northern Peru-Chile trench, seaward of the Lima Basin, Arica Bight, and Iquique Basin, parallel the trend of Nazca plate magnetic anomalies. Where the Nazca Ridge enters the subd uction zone, faulting parallels the trench, probably reflecting a lack of spreading fabric on the ridge. Seaward of the Yaquina Basin, fault ing does not parallel the trench or the spreading fabric, possibly ref lecting stress changes caused by N-S extension across the nearby Menda na fracture zone. These results generally agree with a previous review of subduction-related faulting, which concluded that faults parallel the spreading fabric where it differs from the strike of the dipping s lab by less than 30-degrees.