Numerical simulations about the influence of stress disturbance on earthquake cycle and seismic moment

The influences of stress disturbance on earthquake cycle were studied based on a 2D finite element model by employing a dynamic fault with slip-weakening friction law. Numerical results show that the stick-slip process of the dynamic fault in a model with uniform background stress behaves like typical characteristic earthquakes, which could be influenced by stress disturbance on the fault. Increasing pressure or decreasing normal stress on the fault delays the occurrence of the following earthquake and enlarges its size, which is more prominent if the stress disturbance locates on the critical rupture zone than on pre-seismic slip zone. If the increased pressure locates on the earthquake slip zone and is large enough, part of the dynamic fault could be locked temporally, thus decreasing the following earthquake size, but enlarging the next earthquake. The influence of decreasing pressure on the fault is more complicate than increasing pressure. If the decreased pressure is large enough, an earthquake could be triggered immediately. If the pressure is decreased at earlier stage of an earthquake cycle, the triggered earthquake usually is a small one, and the next earthquake happens at a shorter time than the time interval of the characteristic earthquakes; on contrary, if the pressure is decreased at later stage of an earthquake cycle, a large earthquake will be triggered immediately. If the stress disturbance locates on pre-seismic slip zone or critical rupture zone, a smaller stress disturbance could produce a similar result; and the later disturbance happens, the more prominent the influence is. The influences are the most prominent when disturbance locates on critical rupture zone. It should be pointed out that the influences of stress disturbance are usually confined within one or two earthquake cycles, and the following earthquake cycles are nearly identical with those without stress disturbance.