中国大陆现今水平形变动态特征

Dynamic characters of present-day horizontal deformation in China continent

2001～2004大陆水平应变场大致沿玉树、阿尼玛沁、鲜水河、小江等断裂带形成一条由东西走向转为南北走向的应变高值带.2004～2007高值带向局部收缩,并维持前期高值.新疆于田Ms7.3、四川汶川Ms8.0分别位于该高值带的东段、西段剪应变梯度带上,具备大尺度形变背景.分析认为昆仑山Ms8.1对青藏高原内部块体、川滇块体的相对运动产生重大影响,导致震中两侧一系列断裂带附近区域水平差异运动处于较高水平,印尼Ms8.7地震则有利于上述区域应变能进一步积累.此外,2001～2004、2004～2007应变分布特征总体从无序趋向有序,体现构造应力场经历调整与再积累过程.现阶段太平洋板块、菲律宾板块俯冲作用可能有所增强.

The 2001-2004 horizontal strain field in China continent shows that there is a high value belt which is of EW trend in its west section and SN trend in its east-south section approximately along the Kekexili fault, Yushu fault, Anymaqn fault, and Xianshuihe fault, Xiaojiang fault. This high strain belt tends to shrink and focuses on a smaller region in the 2004-2007 strain field, but the value keeps the same as the prior period. The Yutian Ms7.3 earthquake in Xinjiang Province and Wenchuan MsS. 0 earthquake in Sichuan Province are located in the shear strain gradient zone of the east section and west section of the high strain belt, especially, accounting for the large scale deformation background of the earthquakes. The results imply that the Kunlun MsS. 1earthquake exerts enormous influence on the relative movements between the blocks within the Tibet plateau and Sichuan-Yunnan block, inducing high lever horizontal differential movement of a series faults and their adjacent regions beside the epicenter. And the Indonesia MsS. 7 earthquake favored such strain energy accumulation. On the other hand, the dynamic character between the 2001- 2004 strain field and 2004-2007 strain field suggests that the strain field changed from a disordered fashion to ordered fashion, implying the adjustment process and accumulation process of the tectonic stress field during the whole period. The results show that the subduction of the Pacific plate and Philipine plate may be enhanced recently.