鲜水河断裂带的应力积累与释放
STRESS ACCUMULATION AND RELEASE IN THE XIANSHUIHE FAULT ZONE
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摘要: 本文根据历史地震(Ms6.0)的资料,研究了鲜水河断裂带的地震活动性,并利用断层的位错模式进一步研究该断裂带的应力积累和释放过程.结果表明,该断裂带的强震活动大致以道孚为界,形成北西和南东两个活动地段,呈现南北交替活动的特征.地震能量的这种交替释放似具有准周期性质,Ms7.0级地震的平均复发周期为27.6年.给出该断裂带在三个不同时间段(1700-1811,1816-1967,1816-1982)强震断层作用引起的应力释放图象,讨论了前两个时间段地震应力场对其后发生的第一个大地震的重要影响.计算了1893年以来在断裂带南东段(相对闭锁段)的应力积累,示出相应的最大剪应力和流体静应力等值线图.最后,根据应力积累、附加应力变化、地震活动规律和应变释放曲线特征,估计了鲜水河断裂带的地震趋势.认为在本世纪末,在断裂带南东段的(1)康定-磨西段或(2)道孚-乾宁段或(3)乾宁-康定段将可能发生 Ms=7.40.3地震.Abstract: In this paper, on the basis of historical data of earthquakes with magnitudes M6, the seismicity in the Xianshuihe fault zone has been studied, and the stress accumulation and release in the fault zone has been further studied by using dislocation model of the fault. The results show that in Daofu, the activity of strong earthquakes along the fault is divided into two active segments: the northwestern and southeastern segments. Strong earthquakes occurred alternately on these active segments. The seismic energy release seems to be quasi-periodic, and the average recurrence period of earthquakes with magnitude M7 is 27.6 years. This paper has shown the patterns of stress release due to the strong earthquakes occurring in three different time spans (1700-1811, 1816-1967, 1816-1982), and has discussed the effect of the stress fields due to the strong earthquakes in the former two time intervals on the occurrence of the first large earthquake that follows. The stress accumulation in the southeastern segment of the fault since 1893 has been calculated, and the corresponding contours of maximum shear stress and hydrostatic stress are shown. Finally, according to the stress accumulation, the additional stress changes and the seismicity as well as the characteristics of strain release curves, we have estimated the seismic trend, and believe that a coming earthquake with magnitude 7.1 to 7.7 may occur in (1) the segment between Kangding and Moxi or (2) the segment between Daofu and Qianning or (3) the segment between Qianning and Kangding in the Xianshuihe fault by the end of this century.
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