A Synthetic Seismicity Model for the Northwestern Portion of the Xianshuihe Fault, Southwestern China: Simulation Using the Monte Carlo Method, Based on Historical Earthquake Data

摘要

In order to estimate distributions of recurrence intervals and segment interactions across the four fault segments along the northwestern portion of the Xianshuihe fault (NPXF) in southwestern China, I generate a large number of synthetic earthquake catalogs by sampling recurrence intervals and segment interactions for the four segments within the preferred ranges based on the seismogenic mechanism of fault rupture and interaction. The ranges are derived from previous studies. Those catalogs that are closest to the real historical earthquake catalog consisting of seven strong events of M ≥6:8 during 1792-1981 along the NPXF, are then selected to determine the possible distributions of the intervals and interactions. Finally, I create a synthetic earthquake catalog by using Monte Carlo sampling from the determined distributions of the intervals and interactions. The ～40;000-year simulated seismic activity shows good agreement with the observed data with respect to the following four statistical features. (1) Most events are single-segment ruptures, with few rupturing two or three segments (～8% of simulated earthquakes) and none breaking all four segments simultaneously. (2) The coefficient of variation C_v of the recurrence interval tends to increase with the complexity of a segment or fault. (3) The Brownian passage time distribution represents the best fit for each of the four individual segments, whereas the Weibull distribution matches the entire NPXF best. (4) The next strong event is most likely to occur in the eastern part of the southernmost segment of the NPXF.