地震活动反映的青藏高原东北地区现代构造运动特征

用地震活动资料研究了青藏高原东北地区的现代构造运动特征．地震活动证据表明，青藏高原东北地区活动块体之间是以复杂的变形带接触的．甘-青地块与阿拉善地块之间有一个宽阔的挤压变形带，该挤压带东南端转变为以网络状水平剪切变形为主．甘-青地块与鄂尔多斯地块接触的六盘山地区处于NE-SW向的挤压变形之中．鄂尔多斯地块与阿拉善地块间有一个具有拐折结构的剪切变形带，鄂尔多斯地块的西北角和东南缘处于NNW-SSE方向的受拉伸状态．该区现代构造变形特征可能与青藏高原向东北的挤压作用、鄂尔多斯地块的阻挡作用以及高原物质向东南方向挤出运动有关． 

PRESENT-DAY TECTONIC MOVEMENT IN THE NOR-THEASTERN MARGIN OF THE QINGHAI-XIZANG (TIBETAN) PLATEAU AS REVEALED BY EARTHQUAKE ACTIVITY

WT5BZ]Characteristics of present day tectonic movement in the northeastern margin of Qinghai Xizang (Tibetan) plateau is studied based on earthquake data. Evidence of earthquake activity shows that junctures between blocks in this area consist of complicated deformation zones. Between the Gansu Qinghai block and Alxa block there is a broad compressive deformation zone, which turns essentially to be a network like deformation region to the southeast. The Liupanshan region, where the Gansu Qinghai block contacts the Ordos block, is sufferring from NE SW compressive deformation. Junction zone between the Ordos and Alxa block is a shear zone with sections of variable trend. The northwestern and southeastern marginal region of the Ordos is under NNW SSE extension. The above characteristics of present day tectonic deformation of the northeastern Qinghai Xizang(Tibetan) plateau may be attributed to the northeastward squeezing of the plateau and the resistance of the Ordos block, as well as the southeastward extrusion of the plateau materials.