W.D. Stuart 1979 Changes in the ground elevation observed before and immediately after the 1971 San Fernando, California, earthquake are consistent with a theoretical model in which fault zone rocks are strain-softening after peak stress. The model implies that the slip rate of the fault increased to about 0.1 meter per year near the focus before the earthquake. application/pdf 10.1126/science.203.4383.907 en American Association for the Advancement of Science Strain-softening instability model for the San Fernando earthquake article