兰州邻区活断层潜在地震最大震级及其危险性评估

兰州附近的庄浪河断裂和白银白杨树沟断裂是对兰州市地震安全有一定影响的晚第四纪活动断裂,但沿断裂发生的中强破坏性地震较为复杂甚至不明确。如何评价西部地区此类断裂的最大潜在地震震级及其危险性是地震中长期预测和地震区划研究中较为重要的问题之一。本文借鉴闻学泽等(2007)对中国大陆东部中-弱活断层潜在地震最大震级评估的思路,建立了兰州地区最大地震震级Mmax与断层小区震级-频度关系参数at/b值之间的经验公式;并采用经验公式外推得到庄浪河断裂和白杨树沟断裂的震级上限Mu分别为MS6.9、6.3,进而评估了这两条断裂的地震平均复发间隔和发震概率。

Assessment of Seismic Risk and Maximum Magnitudes of Potential Earthquakes on Active Faults Near Lanzhou City

The Zhuanglang river and the Baiyin Baiyangshu river faults are the late Quaternary faults near Lanzhou city,which affect the safety of the city.But the cause of a medium-strong earthquake along the fault is rather complicated and even uncertain.It is important for us how to assess magnitudes of maximum potential earthquakes and the risks on the faults.The authors make reference to the method that Wen Xueze,et al.(2007)developed to assess magnitudes of maximum potential earthquakes in sub-areas of the moderately and weakly active faults in eastern Chinese mainland,and formed the empirical relationship between the maximum magnitudes M_max and the a_t/b values of the sub-areas' frequency-magnitude relationships in the Lanzhou area.By using the empirical relationship,the authors estimated that the upper-limits M_u of the Zhuanglang river and the Baiyin Baiyangshu river active faults near Lanzhou city are M_S6.9,6.3,respectively.Also they assessed the average interval recurrence time and the probabilities of destructive earthquakes on the faults.