Petrography and Physical Properties of Selected Rock Types Associated with the Hayward Fault, California

Abstract

This report provides brief petrographic descriptions of rock samples collected from the vicinity of the Hayward Fault, Northern California. Two groups of rock samples are represented here:

• A set of six samples that were used for laboratory measurements of P- and S-wave velocity , strength, density, and porosity. This group was examined using standard petrographic microscope, scanning electron microscope (SEM) and electron microprobe techniques on polished thin sections.
• A larger group of samples, most of them 1"-diameter cores, on which density and magnetic susceptibility measurements were made as part of gravity and magnetic surveys of the Hayward Fault. Because this second group of samples received less extensive laboratory study, examination of them was limited to standard petrographic microscope examination of covered thin sections. The density and susceptibility measurements of this second group of samples are included in this report.

First posted October 16, 2001