以鲜水河断裂带中-北段为例探讨强震活动对活动断层大震复发行为的影响

STUDY OF THE INFLUENCE OF STRONG EARTHQUAKE ON THE RECURRENCE BEHAVIOR OF MAJOR EARTHQUAKE ON ACTIVE FAULT——TAKING THE MIDDLE-NORTH SECTION OF XIANSHUIHE FAULT AS AN EXAMPLE

确定影响大地震周期性复发的干扰因素和原因对活动断裂强震危险性评价具有非常重要的意义。文中基于弹性回跳理论,介绍了活动断裂上中强地震活动对大震复发的影响,提出了利用地震矩释放率法和库仑应力改变分别来计算同一断层和周边断层上发生的强震扰动对断层大地震复发的影响时间Δt,并以鲜水河断裂带中-北段为例进行研究。结果表明1904年、1981年道孚段发生的M7.0和M6.9地震导致道孚—乾宁段大地震复发分别延迟约80a和45a;1923年倡促M7.3级和1967年侏倭M6.8级2次强震使得甘孜—炉霍段的大地震复发时间提前约35a。

It is of great significance to determine the factors and causes that affect the recurrence of major earthquakes.This paper introduces the influence of strong earthquake on the recurrence of major earthquakes according to elastic rebound theory,and then proposes to calculate the impact timeΔt respectively from the effect of strong earthquakes on the same and surrounding faults on the major earthquake recurrence by using seismic moment release rate method and Coulomb stress change.In this paper,we studied the change amount of major earthquake recurrence by taking four earthquakes with magnitude greater than 6.5 occurring at different fracture sections of the Xianshuhe fault zone as an example,they occurred on Daofu,Changcu,Zhuwo Fault,respectively.We used seismic moment rate method to calculate the impact timeΔt of strong earthquake on the recurrence of major earthquakes on the Daofu-Qianning Fault.We further discussed the effect of the Coulomb stress change due to the interaction between faults on the recurrence of subsequent major earthquakes.The co-seismic and post-seismic Coulomb stress changes caused by strong earthquake on the surrounding faults on the Ganzi-Luhuo Fault are calculated.With the fault interaction considered,the importance of the interaction between faults in the middle-north section of the Xianshuihe fault zone to change the recurrence of large earthquakes is retested and evaluated.The results indicate that the two strong earthquakes occurring along Xianshuihe Fault in 1904(M=7.0)and 1981(M=6.9)resulted in a delay of 80 years and 45 years of major earthquake recurrence on the Daofu-Qianning Fault respectively,and the M 7.3 earthquake in 1923 and the M 6.8 earthquake in 1967 resulted in an advance of 35 years of major earthquake recurrence on the Ganzi-Luhuo Fault.