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

从哈萨克斯坦、吉尔吉斯斯坦到中国的密集GPS网络所获得的高质量结果揭示了塔拉斯-费尔干纳断层以东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地台之间的辐合速度约为20mm /年，约为印度板块和欧亚板块总辐合速度的一半。来自PI密集网络的GPS速度表明，收敛仅限于少数结构。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一致。PI利用这些新的大地测量数据，结合一个解释弹性应变积累的简单块体模型，来反演该地区地壳块体的运动。值得注意的结果包括Talas-Ferghana断层的右侧运动比以前的地质估计少得多，Ferghana山谷的旋转速度为~0.8度/年（古地质期长期地质速率的一小部分），帕米尔高原和南天山之间的Alay山谷的辐合速度为~20毫米/年，与以前的估计相当。然而，现有的大地测量覆盖范围在西部，穿过Talas-Ferghana断层进入Ferghana盆地，以及南部穿过Alay山谷和南天山并进入帕米尔高原，都比天山中部更稀疏，精度也更低。塔拉斯-费尔干纳断裂带的走滑运动速率、费尔干纳盆地的旋转以及阿莱河谷的辐合并没有得到很好的约束。例如，推断出的费尔干纳盆地的自转速率会有两倍的差异，这取决于使用哪种GPS结果来约束模型。显然，需要更多的观察才能在这一领域取得与在东部取得的结果相当的有用性。此外，建议将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，将提供一个提高精度的综合解决方案。在与吉尔吉斯斯坦的俄罗斯高温物理研究所（IVTRAN）的同事的合作下，PI计划在吉尔吉斯斯坦西部和乌兹别克斯坦建立20个新的站点。位于中国武汉的中国地震局（CSB）将与我们合作，在中国新疆省西北部安装更多的站点（确切的数量和位置将在实地考察后确定）。PI的合作者将调查这些地点，以及GFZ、IVTRAN和CSB之前在该地区安装的现有地点，以揭示天山盆地、Ferghana盆地、帕米尔盆地和塔里木盆地相交区域的运动学。除了分析GPS数据外，他们还将使用简单的基于连续介质力学的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.