Predicting failure in rocks and its implications for predicting earthquakes

Abstract

In the laboratory rock failure can be predicted both in space and in time. The processes leading to failure are well understood and manifest themselves in measurable quantities. Ultrasonic velocity changes and surface strain anomalies are the most reliable indicators of the impeding failure. To a lesser degree and very much dependent on the deformation rate and the moisture content, acoustic emissions cluster in the vicinity of the failure shortly before the rupture occurs. The precursory failure zone has a linear dimension on the order of 1000 grain diameters. If the same physical mechanisms are involved in the Earth as failure is approached, then detailed velocity and surface strain measurements would greatly enhance our ability to predict earthquakes. With the realization of the Global Positioning System and a possible extension to a satellite holographic system, it is now possible to measure surface deformation inexpensively on a densely spaced grid.