中国西部及邻区活动地块边界带现代构造应力场

利用哈佛全球矩心矩张量解数据和许忠淮认为1920mdash;1999年可靠的中国大陆震源机制解数据, 反演了中国西部及邻区活动地块边界带上现代构造应力场．通过对FMSI反演程序多次的输入和检验, 得到了边界带上的应力场．边界带上最大主压应力sigma;1轴绝大多数近水平. 在90deg;E以西的中国西部大陆及邻区, sigma;1轴水平方向基本上为近SN向；在青藏高原的东北部, sigma;1轴水平方向基本上为近NE向；在青藏高原的东南部, sigma;1轴水平方向绕喜马拉雅构造东端顺时针方向旋转．最小主压应力sigma;3轴倾角呈两极分布，西域地块区内活动地块边界带和青藏地块区内东北缘部分段sigma;3轴倾角较陡, 而青藏地块区内sigma;3轴倾角近水平, 所以西域地块区和青藏地块区内东北部相对于其它大部分青藏地块区, 有更多的逆冲地震．应力场在同一个边界带具有非均匀性. 北天山带、南天山带、西秦岭mdash;德令哈带、岷山mdash;龙门山带和安宁河mdash;小江带的非均匀性相对要小一些, 西昆仑带、海原mdash;祁连带、东昆仑带、玛尼mdash;玉树带、澜沧江带和滇西西边界带的非均匀性相对要大, 而喀喇昆仑mdash;嘉黎带和喜马拉雅带的非均匀性最显著．由于震源机制解数据的限制, 本文给出的是边界带上部分段的应力场． 

Contemporary tectonic stress field on boundaries of active tectonic blocks in and around western China

Contemporary tectonic stress field on boundaries of active tectonic blocks in and around western China mainland is obtained from the data of Harvard CMT solution and reliable focal mechanism solutions from 1920to 1999selected by Xu Zhonghuai.We obtained the stress field by testing input and checking FMSI code ( Gephart ) many times.Most of the maximum principalstressσ 1 axes on active tectonic boundaries are horizontal.To the west of 90°E in and around western China mainland,the horizontalσ 1 axes are nearly in N--S direction.In the northeastern area of Qingzang plateau,the horizontalσ 1 axes are nearly NE--SW.In the southeastern area of Qingzang plateau,the horizontalσ 1 axes turn around clockwise around eastern end of Himalaya arc.The minimum principal stressσ 3 axes show two dominant dip angles.In Xiyu active tectonic block region and on some segments of the northeastern edge of Qingzang plateau,the σ 3 axes are steep,while in the Qingzang block region theσ3axes are horizontal. So there are more thrust earthquakes in the Xiyu block region and on some segments of the northeastern edge of Qingzang plateau than in the Qingzang plateau block region.The stress field on the same active tectonic boundary is heterogeneous.On north Tianshan belt,south Tianshan belt,west Qinling-Delingha belt,Minshan--Longmenshan belt and Anninghe--Xiaojiang belt,the heterogeneity is relatively weak.On west Kunlun belt,Haiyuan--Qilian belt,east Kunlun belt,Mani--Yushu belt,Lancangjiang belt and western belt of west Yunnan block,the heterogeneity is relatively strong.The heterogeneity on Kalakunlun--Jiali belt and Himalaya belt is more notable.Due to limited focal mechanism data,this paper only gave the stress field on some segments of the active tectonic block boundaries.