Synchronization of Earthquake Cycles of Adjacent Segments on Oceanic Transform Faults Revealed by Numerical Simulation in the Framework of Rate-and-State Friction

Synchronization behavior of large earthquakes (rupture of nearby faults close in time for many cycles) has been reported in many fault systems. The general idea is that the faults in the system have similar repeating intervals and are positively coupled through stress interaction. However, many details of such synchronization remain unknown. Here, we built a numerical model in the framework of rate-and-state friction to simulate earthquake cycles on the west Gofar fault, East Pacific Rise. Our model consists of two seismic patches separated by a barrier patch, which are constrained by seismic observations. We varied the parameters in the barrier to understand its role on earthquake synchronization. First, we found that when the barrier is relatively weak, synchronization can be achieved by afterslip or post-seismic creep in the barrier patch. Second, static stress transfer can lead to synchronization, opposite to the suggestion by Scholz (2010, https://doi.org/10.1785/0120090309), which was based on results from a spring-slider model using rate-and-state friction. Third, the width of the barrier is more important than its strength. When the barrier is narrow enough (no more than half the width of the seismic patch in our model), the system can achieve synchronization even with a very strong barrier. Fourth, for certain simulations, the interaction between the two seismic patches promotes partial rupture in the seismic patches and leads to complex behavior: the system switches from synchronized to unsynchronized over 10-20 cycles.