GPS Study of the Kinematics of the Intersection of the Tarim, Tien Shan, and Pamir

来自密集的全球定位系统网的高质量结果横跨天山中部，从哈萨克斯坦，经过吉尔吉斯斯坦，直到中国，揭示了塔拉斯-费尔干纳断裂以东的相对简单的运动学图像。几项独立研究的GPS速度一致认为，塔里木盆地和哈萨克斯坦地台之间存在约20毫米/年的会聚，约占印度和欧亚板块之间总会聚的一半。来自PI密集网络的GPS速度表明，收敛局限在少数结构上。从地质研究和大地测量研究中推断出的这些构造的滑动速率非常吻合。PI利用这一新的大地测量数据，结合考虑弹性应变累积的简单块体模型，对该地区地壳块体的运动进行了反演。显著的结果包括：塔拉斯-费尔干纳断裂上的右旋运动比先前的地质估计要小得多，费尔干纳山谷以约0.8度/MYR的速度旋转(与古马克的长期地质速率的一小部分)，以及跨越帕米尔和南天山之间的阿莱山谷的会聚约20毫米/年，与先前的估计相当。然而，西部现有的大地测量覆盖范围，穿过塔拉斯-费尔干纳断裂进入费尔干纳盆地，向南穿过阿莱山谷和南天山进入帕米尔，比天山中部的覆盖范围更稀疏，精度更低。塔拉斯费尔干纳断裂上的走滑运动、费尔干纳盆地的旋转和跨越阿莱山谷的会聚的这些速率并没有得到很好的约束。例如，费尔干纳盆地的推断自转速度相差两倍，这取决于使用哪种GPS结果来约束该模型。显然，需要更多的观测，才能在这一地区获得与东部地区的结果相媲美的结果。此外，拟议对PI的原始GPS数据与其他机构(GFZ和CSB)的原始GPS数据进行联合分析，将提供一个精度更高的组合解决方案。国际和平研究所与吉尔吉斯斯坦的俄罗斯高温物理研究所(IVTRAN)的同事合作，提议在吉尔吉斯斯坦西部和乌兹别克斯坦建立20个新的地点。武汉的中国地震局中国将与我们合作，在中国西北部的新疆中国安装更多的震源(具体数量和地点将在实地考察后确定)。PI的合作者将对这些地点以及GFZ、IVTRAN和CSB先前安装在该地区的现有地点进行调查，以揭示天山、费尔干纳盆地、帕米尔和塔里木盆地相交地区的运动学。除了分析GPS数据外，他们还将使用基于连续介质力学的简单模型来解释他们根据地质运动获得的GPS速度。

High quality results from a dense GPS network spanning the Central Tien Shan, fromKazakhstan, through Kyrgyzstan, and into China, reveal a relatively simple kinematic picture to the east of the Talas-Ferghana fault. GPS velocities from several independent studies agree that there is ~20 mm/yr convergence between the Tarim Basin and the Kazakh platform, about half the total convergence between the Indian and Eurasian plates. GPS velocities from the PI's dense network show that convergence is localized on a handful of structures. Slip rates on these structures inferred from both geologic studies and geodetic studies agree remarkably well. The PI's have used this new geodetic data, in conjunction with a simple block model that accounts for elastic strain accumulation, to invert for the motions of crustal blocks in the region. Notable results include much less right-lateral motion on the Talas-Ferghana fault than the previous geological estimate, rotation of the Ferghana Valley at ~0.8 degree/myr (a fraction of the long-term geologic rate from paleomag), and convergence across the Alay valley between the Pamir and Southern Tien Shan of ~20 mm/yr, comparable to previous estimates. However, existing geodetic coverage in the west, across the Talas-Ferghana fault into the Ferghana basin, and south across the Alay valley and South Tien Shan and into the Pamir, is both more sparse and less accurate than that in the Central Tien Shan. These rates of strike-slip motion on the Talas Ferghana fault, rotation of the Ferghana basin,and convergence across the Alay valley are not well constrained. For example, the inferred rate of rotation of the Ferghana basin differs by a factor of two depending upon which GPS results are used to constrain the model. Clearly, more observations are needed to obtain results in this area comparable in usefulness to those obtained to the east. In addition, the proposed joint analysis of the PI's raw GPS data with that taken by others (GFZ and CSB) will provide a combined solution with improved accuracy. In collaboration with colleagues at the Russian Institute for High Temperature Physics (known as IVTRAN)in Kyrgyzstan, the PI's propose to install 20 new sites in western Kyrgyzstan and Uzbekistan. The Chinese Seismological Bureau (CSB)in Wuhan, China, will work with us to install additional sites in northwestern Xinjiang Province in China (exact number and locations to be determined after a visit to the field). The PI's collaborators will survey these sites, as well as existing sites that GFZ, IVTRAN, and CSB previously installed in the region, in order to unravel the kinematics of the area where the Tien Shan, Ferghana Basin, Pamir, and Tarim Basin intersect. In addition to analyzing the GPS data, they will also use simple continuum mechanics-based models to interpret the GPS velocities that they obtain in terms of geologic motions.