【作者】 丁开华；

【导师】 许才军；

【作者基本信息】 武汉大学 ， 大地测量学与测量工程， 2010， 博士

【摘要】 中国是全球大陆地震最强的地区之一,是一个多地震和强地震的国家。位于其西南的青藏高原是我国地震活动水平最高、强度最大的地区。青藏高原是全球最大的陆-陆碰撞带,内部地质构造复杂,断裂带的构造活动至今依然十分活跃,地壳变形十分强烈,是研究现代板块运动理论、板内变形和板内地震最理想的地区之一以GPS (Global Positioning System)为代表的空间大地测量技术的迅猛发展和广泛应用,提供了大量的大范围、高精度、准实时的观测数据,也为大地测量反演的发展和应用开辟了广阔的前景。GPS资料的空间尺度从区域到全球,时间尺度从数秒、数小时到数十年,长基线相对定位精度可达10-9的量级。所以,GPS手段所获得的高精度、高时空分辨率的现今构造变形的定量运动图像是研究大陆动力学的重要基础数据。因此,本文利用GPS数据来研究青藏高原中东部地区的地壳运动及变形。本文利用武汉大学在青藏高原布设的监测站的六期复测数据,通过高精度GPS数据处理获得了青藏高原的现今地壳运动速度场。采用自洽、统一的参考框架方法对武汉大学在青藏高原布设的监测站的1993、1995、1997、2000、2002及2007年的六期观测数据进行了处理,获得了各监测站的三维运动速率,并根据监测站位置,求得了喜马拉雅块体和西藏块体的运动速率及应变参数。结果显示喜马拉雅块体的南北向缩短速率、东西向伸张速率及隆起速率分别为(19.0±0.5)mm/a、(10.8±0.3)mm/a和(3.6±0.4)mm/a,并以N(33.8±3.3)0E达(-26.6±3.8)×10-9/a的挤压为主,同时兼有(9.4±0.9)×10-9/a的拉伸；西藏块体的南北向缩短速率、东西向伸张速率及隆起速率分别为(9.1±0.6)mm/a、(8.5±0.7)mm/a和(3.3±0.3)mm/a,并以N(55.8±4.3)。E达(-11.4±2.9)×10-9/a的挤压为主,同时兼有(6.2±1.0)×10-9/a的拉伸。分析表明：青藏高原现今地壳运动仍以南北向挤压、东西向拉伸、垂直隆升、东向逃逸为主要特征。本文利用川滇地区的GPS速度场和地震矩张量联合反演了川滇地区的现今地壳运动与形变。在详细划分川滇地区内的各个活动块体的基础上,利用来自中国地壳观测网络在1998-2004年间以华南板块为参考的GPS速度值及来自哈佛大学全球地震中心矩张量目录在1903-2003年间的地震矩张量,考虑了两类数据的权比因子联合反演了川滇地区各活动块体的运动及变形特征：藏东块体、川西块体、滇中块体和印支块体的优势运动方向和速率分别为N97.10E,22.3mm/a、N127.90E,17.9mm/a、N146.70E,15.8mm/a、N167.00E,9.7mm/a。并采用速度剖面法求得各活动断层的错动速率,其中鲜水河断裂的走滑速率和挤压速率分别为(10.0±1.0)mm/a和(2.2±1.0)mm/a,金沙江断裂带和红河断裂带的右旋走滑速率分别为(3.7±1.2)mm/a和(7.3±0.9)mm/a。在此基础上,讨论了川滇地区的变形模式,认为青藏高原的东西挤出速率远小于“大陆逃逸”理论模型所预测的运动速率,而与稳定的华南板块的速度差主要通过川滇地区的顺时针旋转运动和内部的变形运动予以调节和吸收。本文利用汶川地区震后的GPS连续观测资料获得了汶川地震的震后形变场。通过时间序列分析处理了中国地震局以及武汉大学在汶川地震后在沿断层两侧布设的16个连续GPS观测站的观测资料,求得汶川地震震后松弛时间约为38天,并获得了汶川地震的震后形变场,显示了汶川地区震后的地壳运动情况,其中上盘有垂向隆升以及东南向的水平位移。以GPS连续观测站所获得的震后形变场作为约束,采用汶川地震同震研究中得到的断层模型,利用PSGRN/PSCMP程序对由粘弹性松弛引起的震后变形进行模拟,反演出汶川地区地壳的弹性层最佳厚度约为45km,粘弹性层的最佳粘滞系数为1.8×1019Pa·s。更多还原

【Abstract】 China is a region with the strongest earthquakes in the global continent, and a country with many and strong earthquakes. The Qinghai-Tibetan Plateau, lies in the Southwest region of China, with the highest and strongest seismicity. It is a product of the ongoing collision be-tween Indian and Eurasian plates, with complex geological structures,active faults and strong curst motion. It becomes an ideal region for studying on the intra-plate crustal deformation and seismic mechanism.With the rapid development and widespread use of space geodesy techniques, repre-sented by Global Positioning System, it provides many data with large scale, high accuracy and quasi-realtime for the development and application the geodetic inversion. The space scale of GPS data vary from region to the global, and its time scale vary from seconds to years. Its precision of relative positioning for long baseline can reach the magnitude of 10-9. The quantitative image of crust motion with high precision and space-time resolution by GPS, is the important basic data for research on continental dynamics. Therefore, GPS data is used for research on crustal movement and deformation in central and east Qinghai-Tibet Plateau in this thesis.With high precision data process of six repeated GPS observation data, which were col-lected in 1993,1995,1997,2000,2002, and 2007 separately, the present-day 3D crustal move-ment in the Qinghai-Tibetan Plateau is obtained. According to the location of the monitoring sites, the crust motion and strain parameters of the Himalayan sub-block and the Tibetan sub-block are obtained. It shows that the rates of crust motion in the Himalayan sub-block are (19.0±0.5)mm/a, (10.8±0.3)mm/a and (3.6±0.4)mm/a in SN, EW and vertical direction, sep-arately. The Himalayan sub-block is mainly under compressing strain, and the maximum compressing rate is (-26.6±3.8)×10-9/a and with the extension rate of (9.4±0.9)×10-9/a in the direction of N(33.8±3.3)0E. The rates of crust motion in the Tibetan sub-block are (9.1±0.6)mm/a, (8.5±0.7)mm/a and (3.3±0.3)mm/a in SN, EW and vertical direction, sepa-rately. The Tibetan sub-block is mainly under compressing strain, and the maximum com-pressing rate is (-11.4±2.9)×10-9/a and with the extension rate of (6.2±1.0)x10-9/αin the direction of N(55.8±4.3)0E. It also shows that present 3D crustal movement in the Qinghai-Tibetan Plateau is characterized by compression in NS direction, extension in EW direction, and vertical uplift.On the basis of plotting sub-blocks in Sichuan-Yunnan area, by using GPS velocity ob- servations, collected from the Crustal Motion Observation Network of China between 1998 and 2004, and seismic moment tensors, collected from the Harvard centroid moment tensor between 1903 and 2003, the parameters of crust motion in these sub-blocks are inverted. It shows that the predominant direction of crust motion in East-Zang sub-block is N97.10E at the rate of 22.3mm/a, and N127.90E,17.9mm/a in West-Chuan sub-block, N146.70E,15.8mm/a in Mid-Dian sub-block, N167.00E,9.7mm/a in Yinzhi sub-block, separately. Slip rates of some active faults are calculated by velocity profiles. It shows that the slip rate and shortening rate of Xianshuihe fault are (10.0±1.0)mm/a, (2.2±1.0)mm/a separately. And the right slip rates of Jinshajiang fault and Red river fault are (3.7±1.2)mm/a, (7.3±0.9)mm/a separately. Furthermore, the mode of curst deformation in Sichuan-Yunnan area is discussed. The extru-sion velocity of the Qinghai-Tibetan Plateau in EW direction is far slower than the velocity predicted by the continental extrusion model, but adopted by clockwise rotation and inner deformation of the crust in Sichuan-Yunnan area.Using the method of time series analysis, the data of GPS continual observation sites in the zone of Wenchuan Earthquake is processed, and the postseismic displacement of these sites is obtained. The result shows that the relax time of postseismic deformation is about 38 days, and the hanging wall is with the vertical uplift and horizontal movement in south-east direction. Furthermore, adopting the coseismic dislocation model by others’study, using PSGRN/PSCMP procedure, the postseismic deformation caused by the viscoelastic relaxation is simulated. The result shows that the best thickness of the elastic layer is about 45 km, and the best coefficient of viscosity is about 1.8×1019 Pa·s in the zone of Wenchuan Earthquake.更多还原