Research On Nonplanar Fault And EAPFM Of Dynamic Rupture And Radiation Pattern

The varied fault geometry patterns, including stepovers, branches, bends and curved faults are the most important sources of seismic dynamic rupture complex-ities. We proposed an equivalent single planar fault of non-planar faults. Using the heterogeneous distribution of yielding stress on the equivalent single planar fault, the dynamic rupture processes provide similar rupture scenarios and slip s-naps of the non-planar faults. The dynamic rupture processes of non-planar faults are calculated using curved grid finite difference method. Then the pseudo-slip rate distribution are given as a input into the traction-velocity boundary integral equation to infer the distribution of static friction coefficient of the equivalent single planar fault. This provides a different insight into recognize the effect of fault discontinuities on rupture process. Moreover, the radiated seismic waves of both finite models show good coincidence.We give the description of both numerical simulation and geological research on rupture jumping status of stepovers. For non-planar faults, when the rupture reached the end of the nucleation fault, rupture may trigger the secondary fault or die on the main fault. Moreover, if it is triggered, will the rupture continue to propagate? Many geological observations show that nearly all successful rupture jump occurred on stepovers whose stepwidth is less than4-5km. Several au-thors argues that there existed a10km triggered step in Kunlunshan earthquake. Limited to the capability of computation, nearly all authors used2-D models to calculate. We use the curved grid finite difference method to analysis the jumping status of stepovers in half space under slip-weakening friction law. We discussed many factors, including free surface, cohesion force, acceleration distance, normal stress, etc. Based on these simulations, the rupture velocity of rupture front is the key factor that affects the largest jumping distance of stepovers.2km is the largest jumping distance under subshear rupture velocity, while the exist of super-shear rupture permits much larger jumping distance, although most of them still are limited in5km. However, under some extreme condition, with strong energy of supershear rupture, accompanied with free surface supershear rupture and zero cohesion force, the largest jumping distance is14km for extensional steps, which haven’t be exposed by previous authors.We compared the simulated results of branch fault with fem results using boundary integral equation method and generated the static friction coefficient distribution on the equivalent single planar fault. There is an obvious increment of yielding stress at the discontinuity of branch fault, however, it is not very large. Then we designed three different models to investigate the preference of dynamic rupture on branch faults. We found the normal stress change is the key factor affecting the rupture perferrence. According to our study, rupture jumping happens most easily on the condition when the difference between shear stress and dynamic friction is largest. We simulated the dynamic rupture process under the rate-state friction law using boundary integral equation method on a planar fault in3D full space. The results coincides well with the FEM results.At last, we constructed the geometry of1999Izmit earthquake and simulated the dynamic rupture process on it. We inferred there must be a linking segment between Kar amursel fault and Sapanca fault. The slip velocity snap and final slip are shown.