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A VGGNet-based correction for satellite altimetry-derived gravity anomalies to improve the accuracy of bathymetry to depths of 6500 m

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Acta Oceanologica Sinica 2024年第1期43卷 112-122页

作者： Xiaolun Chen Xiaowen Luo Ziyin Wu Xiaoming Qin Jihong Shang Huajun Xu Bin Li Mingwei Wang Hongyang Wan Key Laboratory of Submarine Geosciences Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China Ocean College Zhejiang UniversityZhoushan 316021China Key Laboratory of Ocean Space Resources Management Technology Marine Academy of ZhejiangHangzhou 310012China School of Oceanography Shanghai Jiao Tong UniversityShanghai 200240China School of Civil Engineering and Architectures Zhejiang University of Science and TechnologyHangzhou 310023China National Center for Archaeology Beijing 100013China

Understanding the topographic patterns of the seafloor is a very important part of understanding our planet.Although the science involved in bathymetric surveying has advanced much over the decades,less than 20%of the seafloor has been precisely modeled to date,and there is an urgent need to improve the accuracy and reduce the uncertainty of underwater survey data.In this study,we introduce a pretrained visual geometry group network(VGGNet)method based on deep learning.To apply this method,we input gravity anomaly data derived from ship measurements and satellite altimetry into the model and correct the latter,which has a larger spatial coverage,based on the former,which is considered the true value and is more accurate.After obtaining the corrected high-precision gravity model,it is inverted to the corresponding bathymetric model by applying the gravity-depth correlation.We choose four data pairs collected from different environments,i.e.,the Southern Ocean,Pacific Ocean,Atlantic Ocean and Caribbean Sea,to evaluate the topographic correction results of the model.The experiments show that the coefficient of determination(R~2)reaches 0.834 among the results of the four experimental groups,signifying a high correlation.The standard deviation and normalized root mean square error are also evaluated,and the accuracy of their performance improved by up to 24.2%compared with similar research done in recent years.The evaluation of the R^(2) values at different water depths shows that our model can achieve performance results above 0.90 at certain water depths and can also significantly improve results from mid-water depths when compared to previous research.Finally,the bathymetry corrected by our model is able to show an accuracy improvement level of more than 21%within 1%of the total water depths,which is sufficient to prove that the VGGNet-based method has the ability to perform a gravity-bathymetry correction and achieve outstanding results.

关键词： gravity anomaly bathymetry inversion VGGNet multibeam sonar satellite altimetry

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Methodology for local correction of the heights of global geoid models to improve the accuracy of GNSS leveling

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Geodesy and Geodynamics 2024年第1期15卷 42-49页

作者： Stepan Savchuk Alina Fedorchuk Institute of Navigation Military University of AviationDeblinPoland Department of Higher Geodesy and Astronomy Lviv Polytechnic National UniversityLvivUkraine

At present,one of the methods used to determine the height of points on the Earth’s surface is Global Navigation Satellite System(GNSS)leveling.It is possible to determine the orthometric or normal height by this method only if there is a geoid or quasi-geoid height model available.This paper proposes the methodology for local correction of the heights of high-order global geoid models such as EGM08,EIGEN-6C4,GECO,and XGM2019e_2159.This methodology was tested in different areas of the research field,covering various relief forms.The dependence of the change in corrected height accuracy on the input data was analyzed,and the correction was also conducted for model heights in three tidal systems:"tide free","mean tide",and"zero tide".The results show that the heights of EIGEN-6C4 model can be corrected with an accuracy of up to 1 cm for flat and foothill terrains with the dimensionality of 1°×1°,2°×2°,and 3°×3°.The EGM08 model presents an almost identical result.The EIGEN-6C4 model is best suited for mountainous relief and provides an accuracy of 1.5 cm on the 1°×1°area.The height correction accuracy of GECO and XGM2019e_2159 models is slightly poor,which has fuzziness in terms of numerical fluctuation.

关键词： GNSS leveling Global geoid model gravity anomaly Weight data Correcting data

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Crustal structure of the Qiangtang and Songpan-Ganzi terranes(eastern Tibet) from the 2-D normalized full gradient of gravity anomaly

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Geodesy and Geodynamics 2022年第6期13卷 535-543页

作者： Songbai Xuan Chongyang Shen Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China Institute of Seismology China Earthquake AdministrationWuhan 430071 China

Numerous geophysical studies have revealed the lithospheric structure of the Qiangtang and the Songpan-Ganzi terranes in the eastern Tibetan Plateau.However,crust-mantle evolution and crustal response to the Indian lithospheric subduction are still controversial.Answering these questions requires additional information regarding crustal structure.In this study,the 2-D normalized full gradient(NFG)of the Bouguer gravity anomaly was used to investigate anomalous sources and interpret the crustal structure underneath the Qiangtang and Songpan-Ganzi terranes.The NFG-derived structures with loworder harmonic numbers(N=33 and N=43)showed that an anomalous source beneath the southern Qiangtang terrane had a characteristic northeastward-dipping shape,suggesting the northeastward motion of the crustal material induced by underthrusting Indian lithospheric mantle.The NFG images with harmonic number N=53 showed a large-scale anomalous source in the lower crust of the transformational zone from the Qiangtang terrane to the Songpan-Ganzi terrane,consistent with thickening crust and resistance of lower crustal flow.The anomalous source demonstrated by the NFG results with harmonic number N=71,located in the upper crust underneath the Ganzi-Yushu fault,suggested a seismogenic body of the 2010 M6.9 Yushu event.

关键词： gravity anomaly Normalized full gradient Crustal structures Anomalous sources Qiangtang and Songpan-Ganzi terranes

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Crust and Upper Mantle Density Structures beneath the Eastern Tianshan Region and Its Tectonic Implications

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Journal of Earth Science 2024年第3期35卷 828-838页

作者： Yiming Liu Chao Chen Qing Liang Zhengwang Hu Hubei Subsurface Multi-Scale Imaging Key Laboratory School of Geophysics and GeomaticsChina University of GeosciencesWuhan 430074China

The deformation mechanisms of the Tianshan orogenic belt(TOB)are one of the most important unresolved issues in the collision of the Indian and Eurasian plates.To better understand the lithospheric deformation of the eastern Tianshan orogenic belt,we combined the S-wave tomography and gravity data to develop a three-dimensional(3D)density model of the crust and upper mantle beneath the eastern Tianshan area.Results show that the crust of the eastern Tianshan is mainly characterized by positive density anomalies,revealing widespread subduction-related magmatism during the Paleozoic.We however have also observed extensive low-density anomalies beneath the eastern Tianshan at depths deeper than~100 km,which is likely linked to a relatively hot mantle.The most fundamental differences of the lithosphere within the eastern Tianshan occur in the uppermost mantle.The uppermost mantle layers in the Bogda Shan and Harlik Shan are relatively dense.This is likely associated with an eclogite body in the uppermost mantle.The most significant negative anomaly of the uppermost mantle is however found in the Jueluotage tectonic belt and the central Tianshan Block and is possibly associated with depleted mantle material.We suggest that these differences related to compositional changes may control the strength of the lithospheric mantle and have affected the uplift of the northern and southern segments of the eastern Tianshan after the Permian.

关键词： constrained inversion gravity anomaly three-dimensional lithospheric density structure eastern Tianshan geodynamics geophysics.

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Estimation of Depth to Salt Domes from Normalized Full Gradient of gravity anomaly and Examples from the USA and Denmark

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Journal of Earth Science 2009年第6期20卷 1012-1016页

作者： Hamid Aghajani Ali Moradzadeh 曾华霖 Faculty of Mining Petroleum and GeophysicsShahrood University of Technology School of Geophysics and Information Technology China University of GeosciencesBeijing

We present an estimation of depth of anomalous bodies using normalized full gradient （NFG） of gravity anomaly. Maxima in the NFG map can locate the bodies and indicate their depth. Model calculation using a sphere and application of the NFG method to gravity anomalies over salt domes in the USA and Denmark shows effectiveness of the method. However, the accuracy of depth estimation strongly depends on the number of term N in the Fourier series used to calculate the NFG. An optimum N for the calculation can be given from a test.

关键词： depth estimation anomalous body normalized full gradient gravity anomaly Fourier series.

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Frozen subduction in the Yangtze block:insights from the deep seismic profiling and gravity anomaly in east Sichuan fold belt

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Earthquake Science 2016年第2期29卷 61-70页

作者： Xiaosong Xiong Rui Gao Haiyan Wang Jisheng Zhang Lianghui Guo Key Laboratory of Earth Probe and Geodynamics MLRInstitute of GeologyChinese Academy of Geological SciencesBeijing 100037China School of Geophysics and Information Technology ChinaUniversity of GeosciencesBeijing 100083China

The Sichuan basin is the main part of the middle-upper Yangtze block, which has been experienced a long-term tectonic evolution since Archean. The Yangtze block was regarded as a stable block until the collision with the Cathaysia block in late Neoproterozoic. A new deep seismic reflection profile conducted in the eastern Sichuan fold belt（ESFB） discovered a serials of south-dipping reflectors shown from lower crust to the mantle imply a frozen subduction zone within the Yangtze block. In order to prove the speculation, we also obtain the middle-lower crustal gravity anomalies by removing the gravity anomalies induced by the sedimentary rocks and the mantle beneath the Moho, which shows the mid-lower crustal structure of the Sichuan basin can be divided into eastern and western parts. Combined with the geochronology and Aeromagnetic anomalies, we speculated the Yangtze block was amalgamated by the West Sichuan and East Sichuan blocks separated by the Huayin-Chongqing line. The frozen subduction zone subsequently shifted to a shear zone accommodated the lower crustal shortening when the decollement at the base of the Nanhua system functioned in the upper plate.

关键词： Sichuan basin Frozen subduction Deep seismic reflection gravity anomaly

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Relationship between the regional tectonic activity and crustal structure in the eastern Tibetan plateau discovered by gravity anomaly

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Earthquake Science 2016年第2期29卷 71-81页

作者： Xiao Xu Rui Gao Xiaoyu Guo Key Laboratory of Earthprobe and Geodynamics MLR Instituteof GeologyChinese Academy of Geological Sciences Sinoprobe Center Chinese Academy of Geological Sciences

The eastern Tibetan plateau has been getting more and more attention because it combines active faults,uplifting, and large earthquakes together in a high-population region. Based on the previous researches, the most of Cenozoic tectonic activities were related to the regional structure of the local blocks within the crustal scale. Thus,a better understanding of the crustal structure of the regional tectonic blocks is an important topic for further study. In this paper, we combined the simple Bouguer gravity anomaly with the Moho depths from previous studies to investigate the crustal structure in this area. To highlight the crustal structures, the gravity anomaly caused by the Moho relief has been reduced by forward modeling calculations. A total horizontal derivative（THD） had been applied on the gravity residuals. The results indicated that the crustal gravity residual is compatible with the topography and the geological settings of the regional blocks,including the Sichuan basin, the Chuxiong basin, the Xiaojiang fault, and the Jinhe fault, as well as the Longmenshan fault zone. The THD emphasized the west margin of Yangtze block, i.e., the Longriba fault zone and the Xiaojiang fault cut through the Yangtze block. The checkboard pattern of the gravity residual in the SongpanGarze fold belt and Chuandian fragment shows that the crust is undergoing a southward and SE-directed extrusion,which is coincident with the flowing direction indicatedfrom the GPS measurements. By integrating the interpretations, the stepwise extensional mechanism of the eastern Tibetan plateau is supported by the southeastward crustal deformation, and the extrusion of Chuandian fragment is achieved by Xianshuihe fault.

关键词： Eastern Tibetan plateau Tectonic activity Crustal structures gravity anomaly

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On　the　colocation　iterative　solution　model　and　algorithm　for　gravity　anomaly

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Acta Seismologica Sinica(English Edition) 1996年第4期9卷 76-81页

作者：杨元喜刘长建

An effective method of random approach of gravity anomaly is collocation. To improve the reliability of collocation root, it is crucial to improve the reliability of covariance function of gravity anomaly. In this paper, a set of theoretical models of iterative fitting covariance function and predicting gravity anomaly is established. Through practical calculation, it shows that after finite iterative collocating, they do work well.

关键词： gravity anomaly random approach collocation iterative root covariance.

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Refining geoid and vertical gradient of gravity anomaly

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Geodesy and Geodynamics 2011年第4期2卷 1-9页

作者： Zhang Chijun Bian Shaofeng Yi Zhourun Liu Lingtao Fang Jian Institute of Geodesy and Geophysics Chinese Academy Science Wuhan 430077 China Naval Engineering University Wuhan 430033 China

We have derived and tested several relations between geoid （N） and quasi-geoid （~） with model validation. The elevation correction consists of the first-term （Bouguer anomaly） and second-term （vertical gradient of gravity anomaly）. The vertical gradient was obtained from direct measurement and terrain calcula- tion. The test results demonstrated that the precision of geoid can reach centimeter-level in mountains less than 5000 meters high.

关键词： refine geoid quasi-geoid gravity anomaly vertical gradient

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gravity anomalies determined from mean sea surface model data over the Gulf of Mexico

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Acta Oceanologica Sinica 2023年第12期42卷 39-50页

作者： Xuyang Wei Xin Liu Zhen Li Xiaotao Chang Hongxin Luo Chengcheng Zhu Jinyun Guo College of Geodesy and Geomatics Shandong University of Science and TechnologyQingdao 266590China Land Satellite Remote Sensing Application Center Ministry of Natural ResourcesBeijing 100048China School of Surveying and Geo-Informatics Shandong Jianzhu UniversityJinan 250101China

With the improvements in the density and quality of satellite altimetry data,a high-precision and high-resolution mean sea surface model containing abundant information regarding a marine gravity field can be calculated from long-time series multi-satellite altimeter data.Therefore,in this study,a method was proposed for determining marine gravity anomalies from a mean sea surface model.Taking the Gulf of Mexico(15°–32°N,80°–100°W)as the study area and using a removal-recovery method,the residual gridded deflections of the vertical(DOVs)are calculated by combining the mean sea surface,mean dynamic topography,and XGM2019e_2159 geoid,and then using the inverse Vening-Meinesz method to determine the residual marine gravity anomalies from the residual gridded DOVs.Finally,residual gravity anomalies are added to the XGM2019e_2159 gravity anomalies to derive marine gravity anomaly models.In this study,the marine gravity anomalies were estimated with mean sea surface models CNES_CLS15MSS,DTU21MSS,and SDUST2020MSS and the mean dynamic topography models CNES_CLS18MDT and DTU22MDT.The accuracy of the marine gravity anomalies derived by the mean sea surface model was assessed based on ship-borne gravity data.The results show that the difference between the gravity anomalies derived by DTU21MSS and CNES_CLS18MDT and those of the ship-borne gravity data is optimal.With an increase in the distance from the coast,the difference between the gravity anomalies derived by mean sea surface models and ship-borne gravity data gradually decreases.The accuracy of the difference between the gravity anomalies derived by mean sea surface models and those from ship-borne gravity data are optimal at a depth of 3–4 km.The accuracy of the gravity anomalies derived by the mean sea surface model is high.

关键词： mean sea surface gravity anomaly Gulf of Mexico inverse Vening-Meinesz formula mean dynamic topography satellite altimetry

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