Assessing current faulting behaviors and seismic risk of the Anninghe-Zemuhe fault zone from seismicity parameters

Using the data of regional seismic network, this paper analyzes the current faulting behaviors of different segmentsof the Anninghe-Zemuhe fault zone, western Sichuan, and identifies the likely risky segments for potential largeearthquakes. The authors map the probable asperities from the abnormally low b-value distribution, develop andemploy a method for identifying current faulting behaviors of individual fault segment from the combinations ofmultiple seismicity parameter values, and make an effort to estimate the average recurrence intervals of character-istic earthquakes by using the parameters of magnitude-frequency relationship of the asperity segment. The resultsuggests that the studied fault zone contains 5 segments of different current faulting behaviors. Among them, theMianning-Xichang segment of the Anninghe fault has been locked under high stress, its central part is probably anasperity with a relatively large scale. The Xichang-Puge segment of the Zemuhe fault displays very low seismicityunder low stress. Both the locked segment and the low-seismicity segment can be outlined on the across-profile ofrelocated hypocenter depths. The Mianning-Xichang segment is identified to be the one with potential large earth-quake risk, for which the average recurrence interval between the latest M= 6.7 earthquake in 1952 and the nextcharacteristic event is estimated to be 55 to 67 years, and the magnitude of the potential earthquake between 7.0and 7.5. Also, it has been preliminarily suggested that for a certain fault segment, its faulting behaviors maychange and evolve with time gradually.