关键词: 活动断裂, 地震危险性, 概率模型, 潜在震源区

Abstract: Based on the result of quantitative research on active faults,analysis of regional seismicity,and especially the detailed investigation and systematic summary on paleoearthquake in Urumqi region,the recurrence mode and probability models of Xishan Faults that reflect the seismic,geological and kinemics characteristics are established.The strong earthquake recurrence mode considers the Poisson mode and quasi-period mode and reflects the randomicity and determination with chanciness of seismicity on the fault.The probability model involves two levels of content:analyzing the paleoearthquake data and historical strong earthquake catalog on or near the faults to obtain the mean recurrence interval of surface-rupturing earthquakes(M_S≥6.7),and analyzing the modern instrumental earthquake catalog(1970～present,and the size of these earthquakes is in the range of 2.0～5.0) of potential seismic source zone where the active faults locate.The calculation of seismic hazard probability of active faults utilizes the expert-opinion method to assign different weights to the models such as Poisson model and BPT model,and then incorporate the weighted probability result to construct combined model,which is the core of the method.This data-processing method has two advantages:taking complexity of strong earthquake recurrence mode into consideration and reducing the possibility of overestimating the seismic hazard of active faults.The result shows that the recurrence probability of surface rupturing earthquakes is 4.0% in the coming 100 years,and 3.6% in the coming 50 years.This result is consistent with that of the method based on stress environment analysis.The maximum magnitude of Xishan Faults(belt)is M_S 7.5 estimated from paleoearthquake,dimension and dip-slip rate of fault,which is consistent with the upper limit magnitude of potential seismic source zone where the faults locate.This study integrates the newest research results on regional seismology and geology,better describes the complexity of seismic process along fault to a certain extent,and assesses comprehensively seismic hazards of active faults in Urumqi.This multidisciplinary method can be applied to the region like Urumqi where complete seismogeological data are unavailable.

Key words: active faults, seismic hazard, probability model, potential seismic zone