连续GPS观测研究阿尔金断裂中段现今的造山过程

Refined motion of one fault can be observed by using Continuous GPS profiles or network method.With the CGPS crustal deformation monitoring network which is strict perpendicular to and across the Central the Altyn Fault , North Altyn thrust fault and Qimen Taght Thrust fault which was installed in pre-research stage of this proposal, our purpose is to study the slip rate partion between the Altyn Tagh and Northern Altyn Tagh fault,and possible thrust motion of the North Altyn Tagh fault, meanwhile, it is also important between the Alytn Tagh and Qimentagh Thrust fault. The three dimensional deformation region covers the whole combining near and far field for the Altyn Tagh fault.The horizontal deformation with continuous GPS profiles could provide one more precise approach to understand additive seasonal effects for crustal motion then champion GPS profiles. The vertical deformation's precision could be improved by Surface quality load, such as the atmosphere, rainfall, snow and glacial ablation which also have additive seasonal characteristics. With the combing between continuous GPS observation and tectonic, the active structure of motion framework ,the transpressure model and strain distribution images of the Central the Alytn Tagh fault will be clear in the future. Combing with regional tectonic background, active faults distribution and continuous GPS observed time series data, we construct the active Tectonic image of the central of Altyn Tagh fault, the model of tectonic transpressural motion and regional localized orogenic model in quantification, further to constrain the range uplift velocity in geodetic time scale in crustal deformation.The purpose of this proposal is to understand the slip rate distribution to the Central Alytn Tagh fault due to the thrust systems in the study region. Besides, it is helpful to understand the GPS observed deformation noise affected by seasonal change in northern margin of Tibet Plateau, the localized uplift motion and transit slip near the Atyn Tagh fault to innovate for orogenic theory using continental lithospheric rheology in Tibetan Plateau.

连续GPS观测方法可以观测到阿尔金断裂现今精细运动学状态，其水平向时间序列可约束左旋滑动速率及形变场，垂向时间序列可以约束阿尔金断裂中的现今山脉隆升过程。本申请利用预研阶段架设的垂直于阿尔金断裂中段的连续GPS观测网络研究跨断裂的三维形变场，并合理解释周期项扰动，结合GPS观测网络内各个站点的垂向速率重点分析阿尔金山脉的地形剖面和现今隆升过程相关程度，探讨现今青藏高原北部的局部隆升速率及造山过程。结合区域构造背景、活动断裂展布和连续GPS观测时间序列数据，定量地构建阿尔金断裂中段构造运动、应变分配及区内的局部造山模型，进一步从地壳形变学来约束在短时间尺度上山脉隆升速率。最后，结合岩石圈流变学理论综合分析区域内新构造运动特征及大陆内部岩石圈变形过程，认识青藏高原北部季节变化对GPS观测引起的非构造噪声并提取有效的构造运动信号，认识断裂附近局部隆升活动及潜在起因，试图在造山理论上能够有所创新。

在青藏高原北缘跨阿尔金断裂中段自建9个GPS连续台站并开展观测，根据区域研究特点设计无人值守的观测台站，填补了青藏高原北缘尤其是在阿尔金无人区地壳形变观测研究的空白，积累了宝贵的连续GPS数据，截止2015年7月，共有4年的连续GPS观测。结合使用CMONOC II在研究区及邻域GPS连续台站数据作位置时间序列与速度场解算，获得跨阿尔金断裂中段现今三维形变场。使用三维线弹性后向滑移块体运动模型，反演“塔里木块体”、“北阿尔金块体”、“柴达木块体”和“祁漫塔格块体”的三维块体运动。定量研究结果表明北阿尔金山相对于塔里木盆地有1.32±0.2 mm/yr的抬升速率，相对于柴达木盆地具有0.73±0.3 mm/yr，支持“连续形变与地壳增厚”模型，表明相对塔里木块体，青藏高原北缘地区正在抬升、增厚，以北阿尔金山地区最为明显，抬升速率达~1.3 mm/yr。跨青藏高原北缘的阿尔金断裂、北阿尔金断裂和祁漫塔格断裂近200 km的宽泛变形带内南北向地壳缩短并不明显，缩短量仅为~2.9 mm，且近一半缩短量发生在祁漫塔格山南侧。.GPS观测阿尔金断裂车尔臣河段（~86ºE）剖面(He et al., 2013)表明断裂两侧存在非对称变形特征，采用非对称变形模型反演获得断裂两侧塔里木盆地和青藏高原北部的地壳介质剪切模量差异。结果显示塔里木盆地地壳介质剪切模量约为青藏高原北部剪切模量1.53倍，相应S波波速比值为1.24。本研究运用与地震学完全不同的资料，通过大地测量方法推导青藏高原北部与塔里木盆地的地壳介质力学性质差异，得到与地震学研究S波波速比及其构造物理学解释相当一致的结果。本成果为青藏高原力学演化模型提供新的约束。.同时利用覆盖青藏高原及周边的GPS速度场，计算青藏高原内部应变率场。GPS观测速度场不仅显示了南东东-北西西向的地壳拉张过程，也揭示了青藏高原内部更加重要的地壳减薄过程。结果表明青藏高原内部大尺度范围应变率测量结果的一致性。并且青藏高原内部的拉张应变率观测也相当一致。如果地壳减薄开始于10-15 Ma，并且现今观测得到应变率适用于整个时间跨度，那么地壳累积减薄5.5-8.5 km。应用Airy地壳均衡理论，青藏高原的平均高程将下降近~1 km。青藏高原北部、南部和西南部相似的垂向应变速率也表明在三个区域的地壳拉张、正断裂运动和地壳减薄过程由相同的物理机制所支配。