W.F. Brace J.D. Byerlee 1969 At a confining pressure of a few kilobars, deformation of many sedimentary rocks, altered mafic rocks, porous volcanic rocks, and sand is ductile, in that instabilities leading to audible elastic shocks are absent. At pressures of 7 to 10 kilobars, however, unstable faulting and stick-slip in certain of these rocks was observed. This high pressure-low temperature instability might be responsible for earthquakes in deeply buried sedimentary or volcanic sequences. application/pdf 10.1126/science.164.3880.713 en American Association for the Advancement of Science High-pressure mechanical instability in rocks article