柯坪塔格逆冲推覆系现今变形及其地震构造特征

Kalpintag thrust nappe is of the typical significance in the Cenozoic tectonic evolution of Tianshan mountains. Different from the geomorphic distribution of the South Tianshan arc, the Kalpintag thrust nappe formed a reversed south convex curved distribution, and the interior of the nappe is split into two regions by the Puchang fault which was a north-south trend and is still active today, and the seismic activity in the east-west region is clearly divided. Due to the scarcity of research data, problems such as the origin of the arc structure, the shortening of the current crust, and the movement characteristics of the north-south fault have not yet been clearly determined. We speculate that this may be the result of the elastic deformation of the slippage along the slippery surface of the Tarim Basin. Therefore, it is proposed to study the crustal shortening of several rows of fold anticline belts distributed within the Kalpintag thrust nappe from intensive GPS, InSAR, and level observation results, and analyze slippage of the basement slippage surface with more detailed kinematics characteristics. Features, build a fault motion model. This project hopes to reveal the reasons for the formation of reversed arcs in the course of the Kalpin block intrusion into the Tianshan Mountains in the Tarim Basin, and why there is a near-south-north direction of the Puchang fault between the east-west-arranged fold belts. And why the seismic activity on the east and west sides of the Puchang fault differs. In order to reach a comprehensive and in-depth understanding of the physical mechanism of the current tectonic evolution and crustal deformation of the Kalpintag thurst nappe of the basin-mountain joint of the South Tianshan Mountains. This research should strengthen and improve the study of deformation and seismicity of the piedmont thrust belt in the South Tianshan Mountain, and provide scientific basis for regional earthquake research.

柯坪塔格逆冲推覆系在天山新生代构造演化中具有典型意义。但与南天山弧形地貌分布不同，在其南侧形成了反向南凸的弧形展布，推覆系内部被南北走向（现今以来仍在活动）的普昌断层割裂为地壳缩短变形、地震活动性都有强弱之分的东西两个区域。受限于研究资料的匮乏，反向弧成因及东西区域强弱差异性问题未能清晰厘定。我们推测可能是塔里木沿基底滑脱面滑移积累的弹性变形在不同区域造成的结果。为此，本项目利用密集精细分布的GPS、InSAR及水准观测，从其内部分布的若干排褶皱背斜带的地壳缩短入手，以运动学方法分析基底滑脱面滑移特征，构建断层运动模型。研究将揭示柯坪块体在塔里木盆地挤入天山的过程中形成反向弧的原因;东西向排列的褶皱带之间为何存在一条近南北向的断裂;普昌断裂东西两侧地震活动性为何存在差异等问题。以此加强南天山山前滑脱层对山前逆冲褶皱带变形及地震活动性的控制作用的科学研究，为区域地震研究提供科学依据。

柯坪塔格逆冲推覆系在天山新生代构造演化中具有典型意义，同时具有较大的潜在地震危险性。我们从现今地壳运动的视角，厘定柯坪塔格逆冲推覆系与天山汇聚变形的关系，探讨西南天山地区盆山结合部应变积累方式、幅度与区域地震活动性的内在联系。.通过基金项目的支持，在前人从未开展过观测的区域创新性地开展了有针对性的GPS点位的加密观测工作。在柯坪塔格无人区内围绕南北向的皮羌断裂、柯坪逆冲推覆体及其内部近东西走向的多排褶皱带开展了11条GPS剖面观测。第一次解释了这一区域内部的现今地壳形变运动特征，定量分析了柯坪塔格区域截止2022年最为精细的地壳运动图像，整体变形规律；精细绘制了柯坪块体内部区域应变率场分布图，系统总结了分布特征与地震活动的关系，为开展未来强震活动的预测奠定了基础；.通过研究区内的GPS速度场，我们得到了柯坪塔格前陆冲断带和南天山断裂的南北向缩短速率分别是1.4-3.7mm/a和0.2-2.1 mm/a，认为这一地区现今地壳缩短变化占据了塔里木块体与哈萨克地台汇聚速率的三分之一之多。.柯坪塔格现今复杂的变形模式和沿走向不稳定的缩短速率是由叠瓦状构造的差异逆冲与该区域的先成构造叠加所导致的。西段盆山结合部位的构造容纳了全部的缩短速率，较东段更容易形成应力积累，从而易于产生地震。因此，针对柯坪塔格的地震危险性，应该按照东、西段单独进行评价。.柯坪塔格前陆冲断带形成现今的构造格局，是由于该区域的构造叠加演化特征导致的。新近纪以来，随着天山向南的强烈推挤，不但使柯坪塔格产生强烈的叠瓦状逆冲构造，也使得柯坪塔格和其区域内先存的多条NNW走向的断裂被重新激活。伴随着不均匀的逆冲作用，这些断裂转换为撕裂断裂，调节着逆冲构造向前陆方向的差异位移。皮羌断裂明显地切割了新近系以来的地层和变形。.观测成果也直接应用于新疆的各类地震区域会商研判之中。对未来地震重点监视区的划定给出了意见。项目的实施也为新疆地震局培养了一批具有高水平的研究人才。