Possible Earthquake Rupture Connections on Mapped California Faults Ranked by Calculated Coulomb Linking Stresses

Abstract

Probabilistic seismic hazard assessment is requiring an increasingly broad compilation of earthquake sources. Fault systems are often divided into char- acteristic ruptures based on geometric features such as bends or steps, though events such as the 2002 M 7.9 Denali, and 2011 M 9.0 Tohoku-Oki earthquakes raise the possibility that earthquakes can involve subsidiary faults and/or rupture through iden- tified geometric barriers. Here we introduce a method to discriminate among a wide range of possible earthquakes within a large fault system and to quantify the prob- ability of a rupture passing through a bend or step. We note that many of the conditions favoring earthquake rupture propagation can be simulated using a static Coulomb stress change approximation. Such an approach lacks inertial effects inherent in a full dynamic simulation but does capture many of the empirical observations drawn from examining past ruptures, such as continuity of rake and strike, as well as distance across gaps or stepovers. We make calculations for a test region in northern California and find that the method provides a quantitative basis for ranking possible ruptures within localized fault systems.