[S09-2] Open session: Earthquake generation process – physics, modeling and monitoring for forecast II

[S09-2-05] Fluid injection effects on induced seismic activity in multi-degree-of-freedom rate-and-state model

^○Sergey Turuntaev^{1, 2, 3}, Vasily Riga³ (1.Institute of Geosphere Dynamics, Russian Academy of Sciences, Moscow, Russia, 2.Moscow Institute of Physics and Technology, Moscow, Russia, 3.All-Russian Research Institute of Automatics, Moscow, Russia)

The fluid injection influence on induced seismic activity was studied by numerical calculations of the peculiarities of motions of a system of blocks (consisted from up to 25 blocks) elastically connected with each other and linked by elastic springs to a constant-velocity moving driver (multi-degree-of-freedom spring-block model). The rate-and-state friction model with two-parametric friction law was adopted for description of the friction between the blocks and the substrate. Initially, the block system was in steady-sliding state, then its state was disturbed by the fluid injection and corresponding pore pressure increase. Influences of the model parameters (number of the blocks, the spring stiffness, velocity weakening parameter) on the process of the induced seismicity variations were considered.
It was shown that the considered spring-block system could exhibit different types of the motion patterns. The motion could be periodic or chaotic; the magnitude of the seismic events depends on fragmentation of the fault system (the number of blocks in considered model) and may have different values. The analysis shows, that the stiffness of link between the blocks affects significantly the behaviour of the model and resulting seismicity, so the main seismic activity could appear directly after the start of the fluid injection or in the post-injection phase. Different manifestations of the injection influence on the seismicity are observed also in the real cases. However, the parameters in the rate-and-state model are usually taken from laboratory experiments, and it is hard to believe that one should use the same values to describe the real scale phenomena. Yet our study showed, that it is possible to select more suitable parameters that will allow one to match results of calculations and data of real observations. It can be concluded, that considered model has the potential to be used for the estimations of the possible fluid-induced seismicity activity variations.