13:45 〜 14:00
[S08-21] Feature of cascading rupture frequently observed in Northern California
Understanding if earthquakes of different sizes start in the same way and whether the growth process of the rupture of large earthquakes is predictable are fundamental questions in earthquake source physics, with practical implications for Earthquake Early Warning systems and probabilistic forecasting. Recent studies in Japan have shed light that the onsets of seismic waves from small and large earthquakes exhibit similar characteristics, and proposed a hierarchical patch model. This model indicates the onset of an earthquake does not determine its final size. However, the applicability of the hierarchical path model and the controlling factors remain unclear. A systematic comparison of 24 years of high-sensitivity seismograph records for approximately 75,000 events reveals 125 extremely similar and 1,939 very similar pairs of large (M>=4.0) and small (M<=3.0) earthquakes, co-located within about 100 meters. An extremely high similarity is observed for pairs of earthquakes occurring on simple faults (50 of 65 large events) separated by a long period of up to 24 years, whereas pairs of large earthquakes occurring on complex faults have a low probability of cascading rupture. Estimating the probability of cascading rupture based on fault geometry can improve the predictability of future earthquakes with a more quantitative size estimation.