8:45 AM - 9:00 AM
[S09-1-02] Synchronization of Stick-Slip Oscillator by Periodic External Forces –Implications for Earthquake Activity Rhythms-
Activities of small and large earthquakes and slow slip events (SSEs) have several rhythms, such as periodicity and seasonality, and earthquake recurrences on faults. They are caused by external forces such as tidal forces and interaction between fast or slow slips of earthquakes.
‘Synchronization'is now recognized as a universal concept in nonlinear sciences. In this respect, I investigate responses of stick-slip oscillator to periodic external forces. In the numerical experiments, I examine stick-slip motions of a spring-slider pulling with a constant rate, where the friction following the laboratory-derived rate and state friction law is working on the contact surface between the block and the floor,
I found m:n synchronization, which is called as Devil's Staircase, when applying periodic external forces with the amplitudes of 1/10 and 1/100 relative to the stress changes in cycles. Synchronization occurs in cases of fe:fc(Tc:Te)=m:n (m and n are coprime integers) where fe(Te) and fc(Tc) are frequencies (periods) of external force and simulated system, respectively. In the non-synchronization cases, there appear some complex irregularities in the recurrence intervals with large fluctuations.
Earth and ocean tidal loading has stress with the amplitude of kPa-10kPa, and such loading may cause synchronization of SSE with small stress changes of several 100 kPa. Numerical experiments show a possible existence of repeating large long-term SSEs causing stress perturbation of MPa in the downdip of megathrust zone. My experiments indicate a possible synchronization of the megathrust recurrences. The recurrence intervals of large and megathrust earthquakes have some complex irregularity. These fluctuations may be caused by some complex non-synchronization effects between some adjacent fault segments.
Finally, we add some discussions on the viscoelastic cases where the elastic spring is replaced by a standard linear viscoelastic element.
‘Synchronization'is now recognized as a universal concept in nonlinear sciences. In this respect, I investigate responses of stick-slip oscillator to periodic external forces. In the numerical experiments, I examine stick-slip motions of a spring-slider pulling with a constant rate, where the friction following the laboratory-derived rate and state friction law is working on the contact surface between the block and the floor,
I found m:n synchronization, which is called as Devil's Staircase, when applying periodic external forces with the amplitudes of 1/10 and 1/100 relative to the stress changes in cycles. Synchronization occurs in cases of fe:fc(Tc:Te)=m:n (m and n are coprime integers) where fe(Te) and fc(Tc) are frequencies (periods) of external force and simulated system, respectively. In the non-synchronization cases, there appear some complex irregularities in the recurrence intervals with large fluctuations.
Earth and ocean tidal loading has stress with the amplitude of kPa-10kPa, and such loading may cause synchronization of SSE with small stress changes of several 100 kPa. Numerical experiments show a possible existence of repeating large long-term SSEs causing stress perturbation of MPa in the downdip of megathrust zone. My experiments indicate a possible synchronization of the megathrust recurrences. The recurrence intervals of large and megathrust earthquakes have some complex irregularity. These fluctuations may be caused by some complex non-synchronization effects between some adjacent fault segments.
Finally, we add some discussions on the viscoelastic cases where the elastic spring is replaced by a standard linear viscoelastic element.