The Mechanical Factors Which Influence The Semi-Random Behavior Of Great Earthquakes

Abstract

The apparent randomness in patterns of earthquake activity are modeled using a quasi-static, truss-fault block analogy of earthquake occurrence. The earthquake belt is modeled utilizing a series of fault blocks along a seismic belt can experience either enhanced or suppressed seismic activity immediately after and during the years that follow a modeled earthquake. However, the regions that adjoin the block which has experienced a modeled earthquake, are primarily affected by the enhancing or the suppressive effected of a modeled earthquake. Seismic gaps are attributed to the complex interaction between fault blocks and the manner in which modeled earthquakes redistribute forces to an elastic truss, which represents the oceanic lithosphere. Due to the enhancing and suppressive seismic effects, seismic gaps within the model are filled by earthquakes that occur in a different order from one modeled earthquake to another. Thus the truss-fault block model produces a semi-random pattern of earthquake occurrence, although there are similarities between modeled earthquake cycles. Model behavior is not unlike the space-time distribution patterns observed in nature. Owing to the semi-random character of the model, the recurrence interval within each fault block is different and the recurrence interval changes from cycle to cycle. Also the recurrence interval increases if a fault block is interrupted by the suppressive effects of earthquakes in adjacent areas.