日本3·11大震前后首都圈地区跨断层水准的变形特征及成因探讨

以跨断层水准实测资料为基础,分析2011-03-11日本东部Mw9.0大震前后首都圈地区(114°~119°E,39°~41°N)地壳垂向变形特征。通过构建首都圈地区三维有限元模型,初步探讨跨越不同几何结构断层的测线所表现出的变形特征的动力学成因。结果表明:1)首都圈地区跨断层水准资料表现出群体性变形特征,反映相同的断层运动性质;2)NNE-NE向断层的上盘相对下盘垂向下降,NW向断层上盘相对下盘同样垂向下降,表征着首都圈地区NNE-NE、NW向断层受到不同程度的张性应力作用;3)数值模拟给出的不同方向跨断层测线的垂向变化结果同样表现出与实测结果较为一致的断层正断运动性质,即断层上盘相对下盘垂向下降;4)日本Mw9.0大震造成首都圈地区近E-W向的张性应力是产生首都圈地区跨断层水准资料群体性变化的主要原因。

Deformation Behavior of Cross-Fault Leveling in the Capital Circle Region before and after the March 11, 2011 M9.0 Tohoku-Oki Earthquake and Its Genetic Mechanism

〗In this paper, we explore the crustal deformation in the Capital circle region (114°-119°E, 39°-41°N) before and after the March 11, 2011 M9.0 Tohoku earthquake, according to the cross-fault leveling data in this area. Then we construct the three-dimensional finite element model in the Capital circle region, and preliminarily analyze the dynamic mechanics that reflect the deformation behavior, through the cross-fault observation line in different geometric structures. The results show that (1) the cross-fault leveling data expresses the unanimous characters that reflect the same fault activity type, in which the leveling variation changes from 0.07 mm in Babaoshan and Shangwan sites to 1.09 mm in Jingxi proving ground with the vertical intersecting line| (2) the hanging wall drops vertically relative to the opposite for the NNE-NE and the NW strike faults, which represents the tensional activity| (3) the vertical results of the cross-fault baseline with different directions, which are deduced from the numerical model, also illustrate the same fault activity style as the observed results (i.e., the hanging wall drops vertically relative to the heading wall)| and (4) the nearly EW trending tensile stress is mainly responsible for the unanimous deformation behavior in the Capital circle region.