【摘要】 利用甘肃岷县漳县6.6级地震区所在的青藏块体东北缘地区的区域水准、GPS、流动重力和跨断层短测线等地形变监测资料,结合地质构造、动力环境和已往的研究结果,分析了不同类型资料反映的震前区域性地壳变形背景、断层形变异常特征和可能的机理。结果认为:(1)岷县漳县6.6级地震前西秦岭、六盘山等构造区不同程度地存在着GPS水平挤压闭锁高应变积累、垂直隆升异常高梯度带和重力升、降差异剧烈变化等中长期背景;(2)震前到震时发震断裂附近及其外围相关构造区域断层形变异常在空间和时间上的起伏波动变化显著,尤其是汶川地震以来的波动变化在一定程度上反映了与本区构造比邻的龙门山断裂带剧烈右旋错动对本区的影响,与本次岷县6.6级地震过程有关;(3)本区有地形变监测资料积累以来缺乏6级以上震例,虽然存在不同程度的中长期形变背景异常,但何时进入短期-短临阶段确实很难把握,需要不断积累总结和探索提高。更多还原

【Abstract】 In this study,the regional crustal movement background is analyzed using various types of regional crustal deformation data including vertical deformation,GPS,mobile gravity,and cross-fault short line observation in the Minxian-Zhangxian MS6.6 earthquake zone located at the northeastern margin of the Qinghai-Tibet block.On the basis of regional geological structures,dynamic environment,and existing research findings,the anomaly characteristics of crossfault deformation and its possible mechanism also are discussed.The results show varying degrees of medium-and long-term seismogenic backgrounds in the west Qinling and Liupanshan tectonic province such as a GPS horizontal compresso-locked zone with high strain accumulation and an anomalous GPS vertical uplift belt with a high gradient,in addition to an abrupt change in the pull of gravity prior to the Minxian-Zhangxian earthquake.Moreover,a fault deformation anomaly near the Lintan-Minxian fault caused the earthquake,and its peripheral-related structure realm showed significant temporal and spatial fluctuation up to the time of the earthquake.Particularly since the Wenchuan MS8.0earthquake,the abnormal fluctuations of cross-fault deformation have reflect that the influences from the active dextral rupture of Longmen Mountain seismogenic structure adjacent to the regional tectonic belt have promoted the formation of this tectonic province and the seismogenic process of the Minxian-Zhangxian earthquake.Further,varying degrees of medium-and long-term seismogenic backgrounds exist in the area;therefore,it is difficult to determine the impending earthquake stage because few earthquakes above 6have occurred since the data of crustal deformation in this region has been accumulated.Nonetheless,earthquake data must be continually accumulated,evaluated,and improved.更多还原