Water-induced Weakening of Hornblende and Amphibolite

Abstract

THE disparity between the great laboratory strength of silicate rocks and their apparent weakness in nature, suggested by stress drops associated with earthquakes, remains a persistent problem in tectonics. The strength disparity sometimes approaches three orders of magnitude. Many investigators^1,4 have demonstrated the efficacy of mechanisms that involve water in severely reducing strength. Although amphiboles constitute one of the most common rock-forming mineral groups in the crust and are possible constituents of the upper mantle, little is known about the mechanical properties of this important group of hydrous silicates.