Processing and interpretation of satellite and ground based gravity data at different lithospheric scales
Processing and interpretation of satellite and ground based gravity data at different lithospheric scales
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不同岩石圈尺度的卫星和地面重力数据的处理和解释
DOI：
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发表时间：
2013
期刊：
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通讯作者：
N. Holzrichter
中科院分区：
文献类型：
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作者：
N. Holzrichter
全球重力数据的可用性使得岩石圈的区域调查（<100公里异常波长）成为可能。本文描述了在不同岩石圈尺度上对卫星重力数据进行建模的处理和使用。第一部分显示了来自不同任务（GRACE和GOCE）的卫星重力与安第斯山脉和哥斯达黎加的地面数据的比较。首先，根据大地测量“经典”重力异常和大地测量重力扰动两种大地测量定义编制地形校正后的布格异常。在地势高的地区观测到与地面数据有很大的偏差。其次，与安第斯山脉现有的密度模型（在36°S和42°S之间）的比较证明，卫星重力可以用来模拟区域重力效应（例如俯冲板块、地壳和地幔）。火山后弧在卫星重力数据中没有显示出来。
Global availability of gravity data allows the regional investigation (<100 km anomaly wavelengths) of the lithosphere. This thesis describes the processing and use of satellite gravity data for modelling at different lithospheric scales. The first part shows comparisons of satellite gravity from different missions (GRACE and GOCE) and ground based data in den Andean mountain range and Costa Rica. First, the terrain corrected Bouguer anomaly were compiled from two geodteic definitions: the geodetic "classical" gravity anomaly and the geodetic gravity disturbance. Large deviations from ground data are observed in areas of high topography. Second, comparisons with an existing density model at the Andes (between 36°S and 42°S) prove, that satellite gravity can be used to model regional gravity effects (e.g. subducting slab, crust and mantle). The volcanic back arc do not show up in the satellite gravity data.
The second part of the thesis presents the development of a new accurate algorithm for topographic correction based on a polyhedral representation by triangulation of topographic surfaces. The new algorithm also considers sphericity of the earth, calculates gravity gradients, deals with large datasets and uses an adaptive approach for resampling topography to save computation time. The resampling algorithm bases on a quad tree representation of the topography grid with different resolutions. High resolutions of the topography grid are only considered if it has a significant influence on the gravity at the station. Thus, this approach links the resampling of topography during the calculation with distance and geometry of topography. This leads to an accurate representation of distant terrain and a massive speed up of computation time. The new algorithm will be tested in an area of central Asia in the Himalayan mountain range and compared to existing algorithms. Furthermore, the impact of grid resolutions on the correction will be discussed. Results show significant differences between corrections for different resolutions (e.g. 10 *10^-5 m/s^2 root mean square error between 1 km and 90 m grid resolution). Recalculations of existing Bouguer anomaly compilations show slight differences. Topographic correction of gradients are calculated in the Andes which leads to an improved representation of lithospheric structures in the measured gradients. Another test is conducted at a passive continental margin to investigate the effect of topographic corrections in another environment. Bouguer anomalies of the North Perth basin are recalculated which improves the fit of anomalies and geological structural elements. A 3D model is set up based on ground data to investigate the sedimentary basins at the isostatic state of the area. The results will be compared to satellite data to estimate the usability of satellite data in such an environment. The comparison shows that satellite data can be used to calculate the Moho interface in this area. However, small structures like sedimentary basins do not show up in the gravity field. The results are in agreement with the investigations in the area of an active continental margin (Central Andes).