鲜水河断裂震间形变时空分布特征及地震危险性分析

The Xianshuihe Fault (XSHF) is one of the most active faults at the eastern boundary of the Tibetan plateau with a strike-slip rate of about 10 mm/yr. Large earthquakes (M>7) are absent along the XSHF in about 40 years although two large earthquakes, Wenchuan and Yushu, occurred at its northern and western side respectively. It implies very high probability of large earthquake, which has got substantial attentions over many years. In this proposal, we study the spatio-temporal interseismic deformation and the earthquake hazard on the XSHF using geodetic data from InSAR and GPS collected in the past two decades. The proposal includes six main tasks: 1) Develop an advanced time series analysis algorithm with an accuracy of a few millimeters per year; 2) Make an interseismic deformation time series of the XSHF using InSAR/GPS data; 3) Invert the spatio-temporal distribution of slip rate on the XSHF, and estimate the earthquake potential based on historical earthquakes, long-term geological fault slip rate and the present-day interseismic deformation model; 4) Study stress changes and earthquake hazards along the XSHF associated with the Wenchuan and Yushu earthquakes; 5) Determine a high resolution velocity field covering the XSHF using InSAR rate map and GPS velocities; 6) Determine a time sereis velocity field using CGPS velocities and InSAR rate map time series. Our proposed study will provide important data and explanations for earthquake hazards assessment of the XSHF and the mechanism of the present-day deformation of Tibet.

：鲜水河断裂现今走滑速率约10mm/yr，是青藏高原最活跃的断裂带之一。虽然在其北侧和西部先后发生了汶川、玉树地震，然而在该断裂带上近四十年未有7级以上强震，因此其地震危险性备受关注。本项目利用近20年积累的InSAR/GPS资料研究鲜水河断裂震间形变时空分布特征，并基于此讨论其孕震规律和地震危险性。内容包括：1）研制高精度InSAR时间序列分析方法；2）联合InSAR/CGPS建立鲜水河断裂震间形变时间序列；3）反演该断裂震间滑动速率的时空分布，并结合历史地震、地质长期滑动速率探讨断裂各段的地震危险性；4）研究汶川、玉树地震对鲜水河断裂的影响；5）联合GPS/InSAR平均速率建立该断裂带高分辨率的速度场；6）联合CGPS/InSAR时间序列建立时间序列速度场。本项目有助于进一步认识鲜水河断裂现今构造活动性和青藏高原的形变机制，同时为该断裂现今发生强震的可能性提供关键的基础数据。

鲜水河断裂现今走滑速率约 10mm/yr，是青藏高原滑动速率最快、地震活动最频繁的断裂带之一。采用InSAR/GPS等大地测量方法研究鲜水河断裂带的地壳变形和地震危险性具有重要的意义。四年来，项目组围绕该任务取得的主要成果包括：（1）于2015年和2017年在鲜水河断裂带开展了两期GPS外业观测，收集整理和处理了现有的GPS和InSAR数据，为该地区地壳形变研究积累了重要的大地测量基础资料；（2）提出新的三维粘弹性震间耦合模型，联合GPS/InSAR数据反演鲜水河-安宁河-则木河断裂带震间应变累积的空间分布特征，显示松林口-色拉哈、石棉-冕宁、冕宁-西昌段的三个凸凹体已经处于破裂的临界状态，需要引起人们的高度关注（Jiang et al., 2015, JGR）；（3）收集整理了中国大陆及其邻区近25年的GPS观测数据，得到了大尺度的GPS地壳运动速度场和应变场（Zheng et al., 2017, JGR）；（4）运用改进的InSAR/GPS联合建立速度场的方法获得了Afar地区的三维地壳运动速度场（Pagli et al., 2014, JGR）；（5）利用InSAR技术得到2016门源地震、2017九寨沟地震的同震形变，并由此分析其对周边地震危险性的影响（Wang et al., 2017, IJAEOG）。截止目前，本项研究共发表学术论文5篇，其中国际一流SCI期刊论文4篇，关于联合InSAR/GPS建立川滇地壳运动速度场的论文正在撰写中。项目研究成果为研究鲜水河断裂带及其邻区地壳形变特征和地震危险性提供了重要的数据支持。