ALOS-2和Sentinel-1形变观测揭示的青藏高原西部郭扎错断层三维运动学特征  

Three-dimensional kinematic features of the Gozha Co fault in the western Tibetan Plateau revealed by ALOS-2 and Sentinel-1 deformation observations

作　　者：周宇 黄自成 张培震 Yu Zhou;Zicheng Huang;Peizhen Zhang(Guangdong Provincial Key Laboratory of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai 519080,China;Southerm Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519080,China)

机构地区：[1]中山大学地球科学与工程学院,广东省地球动力作用与地质灾害重点实验室,珠海519080 [2]南方海洋科学与工程广东省实验室(珠海),珠海519080

出　　处：《科学通报》2024年第18期2648-2659,共12页Chinese Science Bulletin

基　　金：国家自然科学基金(42374001);第二次青藏高原综合科学考察研究(2019QZKK0901)资助。

摘　　要：龙木-郭扎错断裂系是青藏高原西部甜水海地块的南边界,其运动学特征研究程度较低.本文利用2014~2022年ALOS-2 PALSAR-2长条带雷达数据,采用小基线集时序处理方法,获取了该断裂系中东段的地表形变速率场,发现其现今应变积累主要集中于郭扎错断层,具有明显的左旋走滑特征,且该断层的中东段存在浅部蠕滑现象.随后,结合已发表的高精度Sentinel-1地表形变速率场所构成的雷达干涉测量数据集作为观测约束,通过使用弹性位错模型获取了郭扎错断层的三维滑动速率空间分布.结果表明:整个断层面的滑动速率具有空间异质性,在孕震层的深度范围内,由断层西段的一个长约40 km的强闭锁区和东段的一个长约100 km的无震蠕滑区所组成,其中无震蠕滑区内的平均速率从断层西侧的部分蠕滑区~2.8 mm/a向东逐渐增加至东侧的完全蠕滑区~5.6 mm/a.最后,进一步计算了郭扎错断层的地震矩积累速率,发现浅部蠕滑段内地震矩积累速率较小,约为(3.3±1.9)×10^(16)N m/a,这与地震台站记录的较低水平地震活动性相一致;而浅部蠕滑段以西的区域具有较高的地震矩积累速率,约为(1.2±0.2)×10^(17)N m/a,考虑到缺少微震记录,该段落的地震危险性需要重点关注.Although faults are thought to be locked by friction during the intervening time between large earthquakes,a subset of continental faults that exhibit aseismic slip in the crust,known as shallow creep,have been documented with the aid of accurate geodetic data.This unusual slip behaviour may control the dynamic processes of earthquake rupture and can help illuminate fault physical properties.Therefore,it has attracted great attention in kinematic and dynamic studies of continental faults over the past decade.Previously,the Haiyuan fault is the only example in the Tibetan Plateau that has been found to exhibit steady-state shallow creep,i.e.creep rate equates to the tectonic loading rate.Our recent study has reported a new shallow creeping fault in the western Tibetan Plateau,the Gozha Co fault,and characterised its creeping rate and temporal evolution based on Sentinel-1 Interferometric Synthetic Aperture Radar(In SAR)data.In this paper,we investigate the Gozha Co fault in greater detail,including its three-dimensional kinematic features and geodetic moment accumulation using a Bayesian inversion approach.We collect JAXA's Advanced Land Observing Satellite-2(ALOS-2)PALSAR-2 data acquired from 2014 to 2022,and derive a rate map covering the central-eastern section of the Gozha Co fault using the Small Baseline Subset(SBAS)method.The ALOS-2 rate map shows that strain is concentrated on the Gozha Co fault and the Longmu Co fault,part of the commonly called Longmu-Gozha Co fault system,has no measurable motion.We then take a velocity profile from the ALOS-2 and Sentinel-1 surface deformation maps to invert fault geometry and creeping rates in order to provide prior information for the subsequent three-dimensional kinematic inversions.Profile inversions show that the Gozha Co fault is a vertical(dip angle 88.1°)left-lateral strike-slip fault(~5 mm/a)with a small thrust component(<1 mm/a).Using these parameters as prior constraints,we derive the three-dimensional slip-rate distribution,which reveals spatial heterogene

关 键 词：郭扎错断层 青藏高原西部 合成孔径雷达干涉测量 浅部蠕滑 地震矩积累 

分 类 号：P542.3[天文地球—构造地质学]