六盘山及其邻区现今大地垂直形变与构造活动研究

Present Vertical Deformation and Tectonic Activity in Liupanshan and Its Adjacent Areas

以六盘山及其邻近地区1970年以来的水准网监测及跨断裂水准测量资料为主,结合GPS水平运动、区域构造和历史强震活动,研究该区域现今大地垂直形变与地壳构造活动特征。分析认为:1)六盘山及其邻区较长时间尺度垂直形变速度场显示的六盘山、西秦岭以及贺兰山等山地相对上升、盆地相对下降的山、盆垂直构造活动差异,体现了该区域现代地壳垂直运动所呈现的继承性趋势特征;2)区域水准垂直形变与GPS水平运动变形综合反映,六盘山、西秦岭等山区现今地壳挤压缩短强烈地带,垂直隆升也相对显著,2者具有一定的共生性特征;3)GPS水平运动速度场在六盘山断裂两侧西强、东弱差异所反映的区域水平运动受阻状态,与六盘山断裂两侧垂直差异活动状况相配合,在一定程度上反映了六盘山构造带应变积累程度较高。这些结果对于该区域未来强震活动研究具有参考价值。

In this paper, we first collect crustal vertical velocity data from leveling network and cross-fault monitoring since 1970s, crustal horizontal velocity from present GPS measuring, the historical earthquake catalogue, and geological maps in Liupanshan and its adjacent areas. Second, we analyze the features of crust movement in the vertical direction and its implication for tectonic activity. The preliminary results indicate that： 1） The features of long-term vertical crust movement in Liupanshan, including the rising in Liupanshan, west Qinling, Helanshan and the sinking in basins, means that the crustal vertical movements are inherited. 2） Considering the GPS horizontal velocity, the crust is squeezing in areas where it is rising. 3） The GPS horizontal velocity in the west of Liupanshan fault is greater than that in the east, implying that the fault of Liupanshan is blocked and the level of accumulated strain is high. These results together indicate a high risk of future strong earthquakes.