Complete Coulomb Failure Stress Changes and Stress Triggering of Yunnan Longling Earthquake Sequence

Abstract

AbstractThe complete Coulomb failure stress changes caused by the 1976 Ms7.3, Ms7.4 Yunnan Longling double main earthquakes are calculated. And dynamic and static stress triggering effects on the after earthquake sequence are studied. The results show that the second main shock is subjected to the triggering effect of dynamic and static Coulomb stresses induced by the first main shock. Among the thirteen strong aftershocks of the double main shocks, 90% of the aftershocks occurred inside the triangle block are subjected to the triggering effect of dynamic and static Coulomb stresses induced by the first or the second main shock. And 2/3 of the aftershocks occurred outside the triangle block are subjected to the triggering effect of dynamic Coulomb stresses induced by the second main earthquakes. The dynamic and static stress triggering effects of the second main earthquake are stronger than the first main earthquake whether in intensity or in extent. In near field the numbers of triggered aftershocks by dynamic and static Coulomb stress are about equal. However the range of triggering effect of dynamic Coulomb stress is larger than static Coulomb stress.