龙门山断裂带及其周边地区重力场和岩石层力学特性研究  

Gravity field and lithospheric mechanical properties of Longmenshan fault zone and its surrounding areas

作　　者：陈石[1] 徐伟民[1] 石磊[1] 卢红艳[1] 郭凤义[1] 

机构地区：[1]中国地震局地球物理研究所,中国北京100081

出　　处：《地震学报》2013年第5期692-703,1,共12页Acta Seismologica Sinica

基　　金：国家自然科学基金青年基金项目(41104046);国家地震科技支撑计划项目(2012BAK19B01-05-02);中国地震局地球物理研究所基本科研业务专项(DQJB12B14;DQJB12B20)联合资助

摘　　要：继2008年汶川MS8.0地震之后,2013年4月20日又发生了芦山MS7.0地震,两次地震的发震构造同属龙门山断裂带.根据最新的重力和地形资料,采用岩石层弹性板模型,计算了龙门山断裂带及其周边地区的二维岩石层有效弹性厚度分布,并从岩石层的力学特征分析了穿过两次地震震中位置的重力剖面特征;结合以往在该地区的研究成果,分析了岩石层的力学变形问题.结果表明,以龙门山为界,四川盆地所在的扬子板块弹性厚度为33(±4)km,龙门山西北的松潘—甘孜地块的弹性厚度为13(±4)km,两侧岩石层存在明显的力学强度差异.包括两次地震震中范围的龙门山断裂带南部区域的有效弹性厚度值小于北部地区,说明该区域的岩石层更容易发生变形,可以解释在构造上具备强震发生的岩石层动力学条件.After the 2008 Wenchuan MS8.0 earthquake, a MS7.0 earthquake occurred in Lushan County, Sichuan Province, on April 20, 2013. The seismogenic structure of the two earthquakes both belong to Longmenshan fault zone. By using the latest gravity and topography dataset, this paper calculates 2D lithospheric effective elastic thickness of the Longmenshan fault zone and its surrounding areas with lithospheric elastic plate model. Based on the lithosphere mechanical properties, the characteristics of two gravity profiles which across the two epicenters are analyzed. And combining with previous researches in the area, the lithospheric mechanical deformation is also analyzed. The results show that, with the boundary of Longmenshan, the effective elastic thickness of Sichuan basin located on the Yangtze Plate is about 33（±4） km, whereas that of the Songpan—Garze block is about 13（±4） km at the northwest of Longmenshan, which indicates that the lithospheric mechanical strengths are obviously different for the two blocks. The effective elastic thickness of the southern Longmenshan region （including the scope of the two earthquake epicenters） is less than the northern, suggesting that the southern region is more prone to lithospheric deformation, which can be used to explain the lithospheric dynamic conditions for great earthquake occurrence in tectonics.

关 键 词：汶川地震 芦山地震 岩石层有效弹性厚度 重力异常 龙门山断裂 

分 类 号：P315.726[天文地球—地震学]