联合卫星重力和GNSS观测的大地震形变分析及位错地球模型精化

Study on the deformation of large earthquakes based on satellite gravimetry or GNSS observations is one of the focuses in the field of the present applications of Astro-geodynamics and Astrometry. Nevertheless, since most of the global huge earthquakes (with the moment magnitude of above Mw8.0) in recent years occurred in land-ocean boundary areas, the investigation of huge earthquake deformation using merely satellite gravimetry or GNSS observations inevitably has its own shortage. The spatial resolution of satellite gravimetry is limited, so it is only sensitive to large-scale signals and cannot represent the complete information. The GNSS observations do not have data in oceanic areas. We aim to solve the above problems and propose to study large earthquake deformation by the combination of GRACE time-variable satellite gravity and GNSS displacement observations. By taking the advantage of the observing coverage for oceanic areas from satellite gravimetry, we propose to complement the GNSS observations with GRACE time-variable measurements, and carry out studies as follows: improving the present fault slip models of huge earthquakes by satellite gravimetry observations, refining the dislocation Earth models with GNSS surface deformation, retrieving post-seismic signals of huge earthquakes by the combination of satellite gravimetry GNSS and constraining the viscosity of the upper mantle, and studying the possibility of detecting the co-seismic deformation signals of fairly huge earthquakes by the combination of GNSS and presently available geodetic VLBI observations. The expected results and conclusions of this study will not only facilitate earthquake disaster monitoring and help better understand earthquake occurrence mechanism, but also contribute to more comprehensive understanding of the Earth’s interior structure and more accurate establishment of the digital Earth model. Therefore, the potential research achievement associated with this study has important scientific significance.

基于卫星重力或GNSS观测的大地震形变分析研究，是现代天文地球动力学及天体测量应用研究领域近期备受关注的问题。然而，由于近年来全球特大地震（矩震级Mw8.0以上）多发于陆海边界区域，单独利用卫星重力或GNSS观测研究大地震形变均难以避免其不足：卫星重力空间分辨率有限，仅对大尺度信号敏感，无法捕捉完全信息；GNSS形变缺乏海域观测。本项目针对上述问题，拟联合GRACE卫星时变重力和GNSS观测，发挥卫星重力的海域观测覆盖优势以弥补GNSS观测的不足，主要研究：卫星重力约束现有大地震断层滑动模型，GNSS地表形变精化地震位错理论的地球分层模型，联合卫星重力和GNSS提取震后信号及反演上地幔粘滞参数，并结合GNSS和VLBI探索巨大地震中远场形变信号检测的可能性。预期研究结果将促进地震灾害监测研究并深化其机制理解，且有助于地球内部结构的准确认知和数字地球模型的精准建立，具有重要科学意义。

本项目联合卫星重力和GNSS观测分析大地震形变以及约束和精化位错地球模型，着眼于目前天文地球动力学应用研究领域的热点问题。项目所开展研究充分利用了GRACE卫星重力的海域观测覆盖优势以及GNSS地表形变观测的高精度特点，在同震和震后变化信号提取及特征分析、区域地壳以及全球分层地球位错模型优化、地表形变分析和物理解释以及基于三维形变的区域地表质量运移反演等方面进行了细致研究。项目主要研究结果包括：1）评估了位错地球模型不同参数对大地震近场及中远场形变的影响，给出了符合地球实际情形的优化模型参数配置；2）发展了顾及地形倾斜效应的区域位错模型，提出斜面体模型以定量估计地形倾斜对同震重力变化的影响，并基于实例证实其显著性；3）基于多源观测约束了震后模型上地幔粘滞参数，结合模拟和实例分析了特大地震远场形变信号检测的临界范围；4）在形变效应精确估计基础上，定量评估了大地震效应对全球海洋质量变化速率的影响，使得海面变化收支不平衡难题的解释更进一步，拓展了三维地表形变的质量运移反演理论及方法，模拟论证了水平形变纳入质量运移高精度反演的优越性。本项目研究结果对地震灾害监测研究及其机制理解以及地球内部结构的精准认知均具有重要的科学意义和实用价值。