基于大地测量约束的天山北麓现今构造运动三维模型构建研究

The earth observation techniques from space that with GPS as a representative had provided revolutionary means for high-precision, high-density, low-cost crustal movement observational studies..Based on the GPS data of Tianshan area that had accumulated many years, supplemented by leveling and relative gravity and other geodetic observational data, and in combination with the survey data of regional active tectonics and high resolution of lithosphere structure materials, the research will study and structure the three-demensional dynamic model of current tectonic movement and crustal deformation on the northern slope areas of Tianshan..On this basis, carry out the following aspects of concrete research:.(1)with constraints based on a variety of geodetic observational data, by using numerical simulation method, quantificationally study the three-dimensional crustal differences in velocity field and the stress-strain field on the northern slope areas of tianshan..(2)make fine study in current tectonics' deformation characteristics and main active faults' movement ways on the north Tianshan region. And discusses the relationships between the vertical crustal deformation, level crustal deformation and dynamic change of gravity field..(3) make quantitative analysis of the temporal and spatial distribution characteristics and evolution laws of the tectonic strain field on the north slopes of Tianshan Mountains, as well as the spatial relationship between the historical earthquake rupture surface and the present distribution of the stress field, then probe the relationship between the fault activity and regional strong earthquakes

以GPS为代表的空间对地观测技术为高精度、高密度、低成本的地壳运动观测研究提供了革命性的手段。本项目将以天山地区积累多年的GPS观测资料为主，辅以水准和相对重力等多种大地测量观测资料，并结合区域活动构造调查资料和高分辨率的岩石圈结构资料，尝试构建天山北麓地区现今构造运动与地壳形变的三维动力学模型。在此基础上，具体开展以下几方面的研究：①基于多种大地测量观测资料的约束，采用数值模拟方法，定量研究天山北麓三维地壳差异运动速度场以及应力－应变场；②精细研究天山北麓地区现今构造变形特征及主要活动断层的运动方式；并探讨垂直地壳形变、水平地壳形变及重力场动态变化之间的相互关系。③定量分析天山北麓构造应变场时空分布特征与演化规律，及历史地震破裂面与现今应力场分布的空间关联性，探讨天山断层活动与区域强震的关系。

利用最小二乘配置方法建立了天山及其邻近地区的模拟速度场模型。结果表明，模拟速度场和实测速度场具有较好的一致性。模拟速度场的变化可以反映天山地区的地壳形变特征，即地壳的汇聚变形不是线性均匀分布，以 为界，西部天山的汇聚速率明显高于东部天山。然后计算了天山地区的地壳应变参数，联合已有的震源机制解结果，认为在最大剪应变极值区和突变区容易造成地震事件的集中。就天山地区而言，乌恰及伊塞克湖地区作为最大剪应变极值区今后发生中强地震的可能将长期存在。. 借助分布在北天山地区的最新GPS站点运动观测资料，利用GAMIT/GLOBK数据处理软件全面地获取了北天山地区现今地壳运动位移场。以速度场为基础，借助弹性半空间位错理论，本课题估算了研究区域内两条具有代表性的主要断裂的现今活动速率。研究表明：博罗科努-阿奇科库杜克右旋走滑断裂的滑移速率东西部运动差异性明显不明显，1944年乌苏南7级强震后，该断层现今表现为震后微蠕滑活动，滑动量东西两部分都在1~2mm/yr；准噶尔南缘断裂现今滑动速率5.6±1.0mm/yr。