利用大地测量观测资料研究青藏高原三维地壳形变及地震危险性评估进展

Progress in Studying of 3D Crustal Deformation and Seismic Risk Assessment of the Tibetan Plateau Using Geodetic Observations

  • 摘要: 青藏高原是一个理想而独特的地球科学天然实验场,青藏高原的地壳形变、物质逃逸模式及地震活动性等科学问题一直是地学界关注的重点。以全球导航卫星系统(global navigation satellite system,GNSS)和合成孔径雷达干涉测量技术(interferometric synthetic aperture radar,InSAR)为代表的空间大地测量技术因其时空分辨率高、覆盖范围广、观测精度高等特点,被应用于现今的地壳形变监测并在地震研究中起着十分重要的作用。首先,综述了青藏高原三维地壳形变研究进展情况,包括青藏高原地壳水平形变的GNSS研究、综合利用GNSS和水准观测资料的青藏高原地壳垂直形变研究、青藏高原InSAR区域形变研究和融合多源大地测量资料构建青藏高原三维形变场等。其次,结合青藏高原三维地壳形变资料介绍了青藏高原活动断裂地震危险性评估的研究进展,讨论了顾及地震应力扰动的概率性地震危险性评估过程以及大地测量观测在地震危险性评估中所起的作用。今后需要加强青藏高原GNSS监测空区的加密观测工作,综合GNSS和InSAR观测结果精化青藏高原的地壳运动与变形模式;开展断裂带“近全地震周期”的大地测量观测研究,分析断裂带“近全地震周期”的形变特征及断层在地震周期内的形变演化过程;利用地震学、地质学、大地测量学等多源海量数据开展基于机器学习的活动断层地震危险性评估。

     

    Abstract: The Tibetan Plateau is an ideal and unique natural experimental field for geoscience research. Scientific issues related to crustal deformation, material escape pattern, and seismic activity of the Tibetan Plateau attract long-term attention from the geologists. Spatial geodetic techniques represented by global navigation satellite system (GNSS) and interferometric synthetic aperture radar (InSAR), with their high spatiotemporal resolution, widely coverage, and high observation accuracy, have been applied to current crustal deformation measurements and play an essential role in seismological research. First, we review the research progress on three-dimensional crustal deformation in the Tibetan Plateau, including researches related to horizontal crustal deformation using GNSS, vertical crustal deformation study using a combination of GNSS and leveling, regional deformation measurements using InSAR, and the construction of a three-dimensional deformation field using multiple geodetic data. Second, in conjunction with three-dimensional crustal deformation, we review the research progress on seismic risk assessment of active faults in the Tibetan Plateau, and discuss the probabilistic seismic risk assessment that considers earthquake stress perturbations. The role of geodetic measurements in seismic risk assessment is also discussed. In the future, more attention should be paid to the following three aspects. First, dense GNSS network should be established in observation gaps to refine the crustal motion and deformation pattern of the Tibetan Plateau. Second, geodetic observations during “quasi-complete seismic cycle” should be conducted to analyze the deformation characteristics and evolution process of fault zones.Third, seismic risk assessment based on machine learning should be developed using multisource data from seismology, geology, and geodetic observations.

     

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