云南地区现今地壳水平运动与变形特征

CURRENT HORIZONTAL CRUSTAL MOVEMENT AND DEFORMATION CHARACTERISTICS IN YUNNAN AREA

利用云南地区 1999、2 0 0 0、2 0 0 1年共 10 0余个测站的GPS资料 ,获得了该区现今水平运动与形变的特征图像。研究结果认为 :①根据变形与运动特征 ,云南地区可划分为 4个运动单元 ,即滇西地区、滇东地区、滇中东北地区和滇中西南地区 ;剔除整体运动后 ,它们的优势水平运动分别为 :滇西地区以 5 .2± 0 .6mm/a向W 31°N运动 ,滇东地区以 4 .8± 1.8mm/a向E2 6°N运动 ,滇中东北地区以 5 .2± 0 .6mm/a向S4 4°E运动 ,滇中西南地区则基本不动。②相邻单元的平均差异运动分别为 :滇西地区相对滇中东北地区的运动为 10 .9± 1.1mm/a ,方向为W 39°N(张性右旋 ) ,相对滇中西南地区的运动为 5 .3± 1.3mm/a ,方向为W 4 1°N(右旋 ) ;滇中东北地区相对滇中西南地区的运动为 5 .6± 1.6mm/a ,方向为E36°S(左旋 ) ;滇东地区相对滇中东北地区的运动为 6 .2± 1.6mm/a ,方向为N3°E(左旋 )。③从断裂走滑活动看 ,红河断裂两侧的差异运动并不是由红河断裂的活动所形成的 ,而是在很广阔的空间上自西向东渐变而成的 ,跨距达数百km ;小江断裂两侧的差异运动也非完全是小江断裂本身的活动 ,差异运动的渐变空间至少在 6 0km以上。④云南地区的地壳运动方式可能是“断块活动”和“连续变形”的组合 ,或许“连续变形”?

The characteristic pattern of current horizontal movement and deformation in Yunnan area are obtained from the GPS data observed at more than 100 stations in 1999, 2000 and 2001.The pattern is described as follows.(1) According to the characteristics of deformation and movement, Yunnan area can be divided into 4 moving units which are Dianxi (western part of Yunnan) area, Diandong (eastern part of Yunnan) area, Dianzhong-northeast (northeastern part of central Yunnan) area and Dianzhong-southwest (southwestern part of central Yunnan) area. After deleting the entire movement, their dominate horizontal movements are shown as the motion toward W31°E with an amount of 5.2±0.6 mm/a in Dianxi, the motion toward E26°N with a magnitude of 4.8±1.8 mm/a in Diandong area, the motion toward S44°E with a level of 5.2±0.6 mm/a in Dianzhong northeast area, and Dianzhong southwest area is basically stable. Two of the three major boundaries between the areas belong to Honghe fault and Xiaojiang fault. (2) The average differential movements of the adjacent units are 10.9±1.1 mm/a trending W39°N (tensile right lateral) for Dianxi area relative to Dianzhong northeast area and 5.3±1.3 mm/a trending W41°N (right lateral) for Dianxi area relative to Dianzhong southwest area, 5.6±1.6 mm/a trending E36°S (left lateral) for Dianzhong northeast area relative to Dianzhong southwest area, and 6.2±1.6 mm/a trending N3°E (left lateral) for Diandong area relative to Dianzhong northeast area. (3) Considering from the strike slip of the faults, the differential movement on both sides of Honghe fault is not due to the activity of Honghe fault itself, but occurs gradually from the west to the east in a vast range over several hundreds kilometers. Similarly, the differential movement on both sides of Xiaojiang fault does not totally result from its own activity and the range of its progressive differential movement is at least more than 60 km. (4) The normal activity pattern in Yunnan area may be the integration of 'block activity' and 'successive deformation', and the pattern of 'successive deformation' may be more obvious. (5) The principal compressive strain in Yunnan area is (-14.1±5.2)×10\+\{\{-7\}\}/a trending S 5°E, principal tensile strain is(23.5±4.0)×10\+\{\{-9\}\}/a, surface strain is (8.9±6.6)×10\+\{\{-9\}\}/a and the maximum shear strain is (37.1±6.4)×10\+\{\{-9\}\}/a.