EVIDENCE FOR CHAOTIC FAULT INTERACTIONS IN THE SEISMICITY OF THE SAN-ANDREAS FAULT AND NANKAI TROUGH

INTERACTIONS between fault segments are one of the main sources of complexity in the seismicity of active tectonic regions. Such interactions are likely to influence the spatial and temporal patterns of earthquakes. Here we examine the dynamical behaviour introduced by fault interactions using a simple spring-loaded, slider-block model with velocity-weakening friction. The model consists of two slider blocks coupled to each other and to a constant-velocity driver by elastic springs. For an asymmetric system in which the frictional forces on the two blocks are not equal, the solutions exhibit chaotic behaviour. The system's behaviour over a range of parameter values seems to be generally analogous to that of weakly coupled segments of an active fault. We see similarities between our model simulations and observed patterns of seismicity on the south central San Andreas fault in California and in the Nankai trough along the coast of southwestern Japan. © 1990 Nature Publishing Group.