DynCFS: a program for modelling dynamic Coulomb failure stress changes in layered elastic media

SUMMARY Coulomb failure stress change (ΔCFS) quantifies the earthquake-induced difference of shear stress and frictional resistance on a receiver fault, with the latter being proportional to the effective normal stress change. ΔCFS has become a widely used measure for studying earthquake triggering, dynamic rupture processes and earthquake-induced secondary disasters. In simple layered or uniform half-space media, methods for computing static ΔCFS have been well established, with programs such as Coulomb3, PSGRN-PSCMP and AutoCoulomb being widely used. In contrast, dynamic ΔCFS evaluation generally relies on numerical discretization schemes, such as finite-difference, finite-element, boundary-element and discontinuous Galerkin methods, which, while suitable for complex structures, are computationally expensive. To overcome these limitations, we develop DynCFS, a user-friendly, Green’s function based and therefore computationally efficient program for calculating both static and dynamic ΔCFS in layered elastic media. The tool enables rapid assessment of dynamic triggering effects, both between successive earthquakes and among multiple sub-events or faults during an earthquake.