Slip-Parallel Seismic Lineations on the Northern Hayward Fault, California

Authors

Felix Waldhauser, U.S. Geological Survey
William L. Ellsworth, U.S. Geological Survey
Alex Cole, U.S. Geological Survey

Date of this Version

1999

Comments

Published in GEOPHYSICAL RESEARCH LETTERS, VOL. 26, NO. 23, PAGES 3525-3528, DECEMBER 1, 1999

Abstract

A high-resolution relative earthquake location procedure is used to image the fine-scale seismicity structure of the northern Hayward fault, California. The seismicity defines a narrow, near-vertical fault zone containing horizontal alignments of hypocenters extending along the fault zone. The lineations persist over the 15-year observation interval, implying the localization of conditions on the fault where brittle failure conditions are met. The horizontal orientation of the lineations parallels the slip direction of the fault, suggesting that they are the result of the smearing of frictionally weak material along the fault plane over thousands of years.