Fault Resonance Process and its Implication for Active Fault Systems

Abstract

Plate tectonics is the main driving force for lithospheric deformation and occurrence of seismicity. In addition to the tectonic loading, various periodic exogenous stress perturbations (e.g., hydrological loading, snow-induced loading, reservoir-induced loading, atmospheric loading, etc.) also influence the fault dynamics and modulate the seismicity. However, the exact response and feedback mechanism related to the seismicity modulation to such exogenous stress perturbations remain elusive. Moreover, the contrast in seismicity modulation for different types of tectonic domains, including plate boundaries, stable plate interiors, or diffuse deformation zones on Earth, and the different exogenous processes involved in the seismicity modulation in planetary bodies and their natural satellites remains debated. Also, there is an absence of a unified model for the seismicity modulation linked to the planetary objects and their satellites based on the observational, theoretical, and mechanical framework. In the present work, a theoretical model (i.e., fault resonance destabilization model) has been developed incorporating rate-state-dependent friction to understand the fault dynamics and modulation of seismicity influenced by the various periodic exogenous stress perturbations. Further, the diversity in seismicity modulation in plate boundary, plate interior, or diffuse plate boundaries and other planets and their natural satellites is also investigated based on the observational and theoretical framework. Based on the fault resonance destabilization model, it has been observed that the slip of fault is resonated by the periodic exogenous stress perturbation, depending upon the stiffness of the fault and the critical period of excitation. The process also depends upon other several physical parameters, i.e., relative plate motion, effective normal stress, steady-state coefficient of friction, frictional parameter and critical slip distance. The impact of these physical parameters on fault resonance destabilization model has been thoroughly investigated and found that a strong amplification of shear stress and amplitude of velocity perturbation is perceived from the fault system with decreasing effective normal stress, frictional parameters, and an increasing relative plate motion. Whereas the steady-state coefficient of friction and critical slip distance has a minor role in the resonance destabilization model. Moreover, the presence of anomalous fluid-rich crust at deeper levels of the fault possibly places the fault segments in the conditional stable frictional regime, which is very sensitive to periodic exogenous stress perturbation and modulates the seismicity by fault resonance process. Further, it has been found that stable plate interior regions and diffuse deformation zones appear to be more sensitive to long-period seismicity modulation in response to naturally reported harmonic forcing, while short-period seismicity modulation appears to be less sensitive. In contrast, relatively faster-moving plate boundary regions are equally susceptible to both short-period and long-period seismicity modulation processes in response to stress perturbation from natural harmonic forcing. This demonstrates the capability of the resonance destabilization model in understanding the fault dynamics and seismicity modulation process on Earth. In addition, it has been shown from the gravity-induced resonance destabilization model that the effective area of the non-resonance domain increases with increasing gravitational acceleration, and the gravity-induced resonance destabilization model appears to be better in agreement with the diversity in seismicity modulation linked to planetary bodies and their natural satellites. Finally, it has been suggested that the present resonance destabilization model can produce comprehensive results linked to seismicity modulation by different exogenous processes in different planetary environments.