TEMPORAL PATTERNS OF LARGE INTRAPLATE EARTHQUAKES AND THE POSSIBLE CAUSES (Invited Presentation)

Earthquake recurrence interval is a fundamental concept of current earthquake models and a key parameter in earthquake hazard assessment. Whereas much effort has been devoted to estimate and refine the recurrence interval of large earthquakes on various faults, increasing evidence, especially from intracontinental faults, starts to paint a different temporal pattern: clusters of earthquakes within short periods, separated by long periods of quiescence. This pattern can be mathematically described by the Cantor function, or the devil’s staircases, which is a fractal property of complex dynamic systems in nature. Whereas the pattern of devil’s staircase is best shown by intraplate earthquakes, it is observed for large earthquakes in all settings, from global scale to different tectonic regions to individual faults. The average length of the quiescence periods seems to be inversely related to the rates of tectonic loading. Thus large earthquakes in stable continents have longer quiescent periods than those in tectonically active continents. We show that these temporal patterns can be characterized by two parameters, the burstiness parameter that measures the departure of the earthquake sequences from that of a Poisson process, and the memory factor that indicate the tendency of a short (long) interevent time to be followed by a short (long) interevent time. Based on the earthquake catalogs, it is possible to forecast statistically the future temporal behavior of large earthquakes for a given fault system. We also developed a geodynamic model to investigate the underlying physics controlling the temporal patterns of seismicity. Our preliminary results confirm that tectonic loading rate is the key parameter for the length of the quiescent periods, and viscous relaxation and fault interaction are key processes for earthquake clustering.