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Title:: Time Sequence Features of Fault Deformation of Main Fractures in the Northeastern Margin of Qinghai-Tibet Block and Their Relationship with Strong Earthquakes

Author(s):: ZHANG Xi¹; XUE Fu-ping²; WANG Ji-ying²; (1.Institute of Earthquake Prediction,CEA,Beijing 100036,China)(2.The Second Monitoring and Application Center,CEA,Xi'an 710054,Shaanxi,China)

Keywords:: cross-fault strain intensity ratio; time sequence change; difference between fault segments; example of earthquake; northeastern margin of Qinghai-Tibet Block

摘要:: 利用青藏块体东北缘地区20世纪80年代末至2007年底的跨断层短水准流动观测资料,借助应变强度比指标,分析了该区主要活动断裂带的构造变形动态演化特征和分段差异性及与强震的孕育—发生过程的关系。结果表明:① 各断裂带、断裂段应变强度比时序曲线对其上或边缘附近发生的5.8级以上地震反映较好,震前数月至1年左右时间内基本对应“明显上升—均值线以上峰值—回落”的过程; 而断裂带(段)之间应变强度比显著差异对其交汇区及附近强震有一定预示意义。② 昆仑山口西、玉门、民乐地震相继发生后,构造应力场经过一段时间的调整,目前青藏块体东北缘总体上处于新一轮能量积累状态,其中,祁连山断裂带—海原断裂和西秦岭北缘断层尤为明显。

Abstract:: We study the dynamic evolution features of the tectonic deformation of main active faults in the northeastern margin of Qinghai-Tibet Block,the difference between fault segments,and their relationship with the development and occurrence of strong earthquakes,using the strain intensity ratio values calculated from mobile cross-fault short-leveling observational data from the late 1980s to the end of 2007.The results are as follows:① Nearly all strain intensity ratio-time curves of faults or segments reflect the process as“obviously rising-rising to peak above average line-dropping” in several months to about one year before the earthquakes with M≥5.8 on the fault(segment)or nearby.The distinct difference of strain intensity ratio between faults or segments has certain prediction significance for the strong earthquakes in the meeting region of faults(segments)or nearby.② The northeastern margin of Qinghai-Tibet Block,especially the Qilianshan-Haiyuan fault zone and the northern margin fault of the West Qinling mountains,shows a new round of energy accumulation through the adjustment of tectonic stress field after the West Kunlun,Yumen,and Minle earthquakes.