Long-term slip movements along a zone of four parallel faults are simulated using a 2-D deterministic model. Both antiplane and inplane cases are considered for two different situations of close and distant faults. Fault interactions caused by internal stresses are weaker in the case of distant faults; therefore, we can determine their role played during the system evolution. Slip movements patterns obtained for the antiplane case show that driving tectonic forces lead the system towards a periodic, regular regime, whereas the interactions due to internal stresses play a role of random fluctuactions and destabilize the system behavior. More detailed studies of energy release patterns obtained for the inplane case show, both for regular and irregular regime, calm periods of the same length in which stresses are being built up.
3D model of interacting faults is presented The use of the slip-weakening friction law, tectonic loading from the sides of a fault zone, and continuous time formulation of governing equations are its major ingredients. The model can be used for simulations of seismic activity both in time scales of single earthquakes, earthquake cycles, and a long-term system evolution. It allows to study time variations of energy release and tectonic stresses, as well as patterns of slips, slip rates and internal stresses measured at individual locations. Results of such an analysis are presented in Part II of this paper.
Long-term seismic activity is simulated using a 3D model of interacting faults presented in Part I of this paper. It is show that the system can generate complex behavior, with earthquakes of all sizes, characteristic earthquake cycles with features changing from one cycle to another, and interrelations between local quantities in qualitative agreement with laboratory data. By comparison of a single, two distant and two close fault behavior the role of fault interactions is studied. Interactions with a secondary fault, despite its low activity, change patterns of seismicity generated by the system.
The ratio of radiated seismic energy and seismic moment estimated for global sets of earthquakes does not exhibit any systematic changes with seismic moment. In contrast, for regional sets of earthquakes the ratio decreases with decreasing moment. This paper proposes a statistical relationship among radiated energy, seismic moment, and source dimension: Ea M0(1.5) / r which is consistent with both kinds of data. The relation is explained by a fault zone model based on the slip-dependent constitutive law and the overdamped dynamics approximation. Since potential damages caused by an earthquake are related to the radiated seismic energy, the derived relation can help to estimate them if the expected earthquake source dimension and moment release are known.
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