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An overview and perspective of identifying lunar craters

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Science China Earth Sciences 2024年第5期67卷 1395-1416页

作者： Yan JIANG Changyi Xu Ling CHEN State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100029China Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100049China

The spatiotemporal evolution of lunar impact craters is crucial for investigating lunar interior structure,internal and external dynamic processes,and interplanetary impact history.Advances in lunar crater identification are reviewed based on topography and gravity data,and the features and mechanisms of topographic or buried craters are analyzed regarding morphology,gravity anomalies,gravity gradients,and the underlying crust-mantle interface relief.Based on the compiled crater catalog,the early lunar impact flux and thermal evolution are further discussed according to the basin ages and their interior structures.For some ancient impact basins,the crater size-frequency distribution measurements revealed age discrepancies from previous studies,suggesting that the lunar late heavy bombardment event started at~3.95 Ga.The degraded bulge structures of the crust-mantle interface beneath mare basins reveal that these basins formed on the lunar crust surface under high-temperature conditions and underwent prolonged relaxation compared to highland basins.Finally,we reveal that the up-to-date identification of lunar buried craters remains inaccurate and incomplete,preventing us from accurately reconstructing lunar and interplanetary impact histories.Therefore,we propose that a gravity model constructed using localized orthogonal basis functions can be useful for identifying lunar craters.

关键词： Moon gravity field Craters Impact flux Early evolution

Analysis of the impact on the gravity field determination from the data with the ununiform noise distribution using block-diagonal least squares method

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Geodesy and Geodynamics 2016年第3期7卷 194-201页

作者： Wei Liang Jiancheng Li Xinyu Xu Yongqi Zhao School of Geodesy and Geomatics Wuhan University State Key Laboratory of Information Engineering in Surveying Mapping and Remote Sensing Wuhan University

The block-diagonal least squares method, which theoretically has specific requirements for the observation data and the spatial distribution of its precision, plays an important role in ultra-high degree gravity field determination. On the basis of block-diagonal least squares method, three data processing strategies are employed to determine the gravity field models using three kinds of simulated global grid data with different noise spatial distri- bution in this paper. The numerical results show that when we employed the weight matrix corresponding to the noise of the observation data, the model computed by the least squares using the full normal matrix has much higher precision than the one estimated only using the block part of the normal matrix. The model computed by the block-diagonal least squares method without the weight matrix has slightly lower precision than the model computed using the rigorous least squares with the weight matrix. The result offers valuable reference to the using of block-diagonal least squares method in ultra-high gravity model determination.

关键词： Block-diagonal least squaresmethod Precision distribution Parameter sequence gravity anomaly gravity field

gravity and magnetic field characteristics and regional ore prospecting of the Yili ancient continent, West Tianshan, Xinjiang Uygur Autonomous Region, China

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China Geology 2020年第1期3卷 104-112页

作者： Xue-zhong Yu Yi-yuan He Meng Wang Jian Zhang Xuan-jie Zhang Zheng-guo Fan Aero Geophysical Survey and Remote Sensing Centre for Natural Resources Beijing 100083China School of Earth Sciences East China University of TechnologyNanchang 330032China

Gold,iron,copper,lead-zinc and other mineral exploration in West Tianshan,Xinjiang Uygur Autonomous Region,has made remarkable progress in recent years.However,due to the dispute on the tectonic division of West Tianshan,the ore-controlling factors and the regional metallogenic laws are controversial.The authors analyze regional gravity data and notice that the high-value region corresponds to the Yili ancient continent,thus the southeastern boundary of the Yili ancient continent is delineated.Comparative analysis of gravity,aeromagnetic and geologic data reveals that the Tulasu basin,where some medium to large epithermal gold deposits locate,lies above the Yili ancient continent;the Yili Carboniferous-Permian rift extends in E-W direction,numbers of copper deposits have been found in the mid-west section of the rift which lies above the Yili ancient continent,whereas few copper deposits have been discovered in the east section which is outside the Yili ancient continent.Accordingly,the Yili ancient continent may be rich in gold,copper and other metal elements;the metal-bearing hydrothermal solution moves up with the activity of magmatism,and deposits in the favorable places(the Tulasu basin and the Yili Carboniferous-Permian rift),forming numerous small and medium gold,copper deposits,as well as some large and super-large gold deposits.Therefore,the tectonic-magmatic hydrothermal zone above the Yili ancient continent should be the prospective area for epithermal gold and copper polymetallic deposits.

关键词： Yili ancient continent Yili Carboniferous-Permian rift gravity field Epithermal gold deposit Copper polymetallic deposit Geophysical and remote sensing survey engineering Xinjiang Uygur Autonomous Region China

Study on the gravity field and Deep-Seated Crustal Structure at the North Margin of the Qinghai-Tibet Plateau

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Continental Dynamics 1997年第1期 29-38页

作者： MENG Lingshun (Geophysical Department, Changchun Geological College, Changchun 130026, China) CUI Junwen (Institute of Geology, Chinese Academy of Geological Sciences (CAGS), Beijing 100O37, China)

Based upon the 1:500,000 gravity profiles, surveyed along both the Lao Mangnai--Argan line across the Altun Mts. and the Golmud--Ejin Qi line across the Qinan Mts. and Qaidam basin, with the regional gravity field and the corresponding geological data of the Altun Mis. and the Qilian Mts. taken into cnosideration, a study has been made on the gravity features of the Qinghai-Tibet Plateau’s north made. This area has been divided into the following five geo-tectonioc units: the Qaidam basin, the Altun fault system, the mid-south Qi- lian terrane, the northern Qilian fold belt and the southern margin of the Tarim basin. The Airy isostatic anomaly in this area has been calculated and analyzed. The occurrence of the negative isostatic anomaly is probably related to the relative depression of the inner zone and the thick sediments resulting from the thrusting in the upper crust, as well as to the thickening of the lower crust brought about by the subduction of the Tarim plate; while the occurrence of the low positive isostatic anomaly is originated from the tectonic emplacement of the frontal typhonic rocks, resulting from the thrust spreading of the upper crust The Altun fault zone, the Hexi Zoulang’s south margin and the North Qilian fault zone are considered to be the dynamic boundary of the northern margin of the Qinghai-Tibet plateau.

关键词： Qinghai-Tibet plateau gravity field isostatic anomaly,. crustal structure Moho

The Effect of High gravity field on the Hydrothermal Preparation of the Nanostructured Materials

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The Effect of High Gravity Field on the Hydrothermal Prepara...

Novel model of thermo-magneto-viscoelastic medium with variable thermal conductivity under effect of gravity

中国材料大会2012

作者： Wenjun Li Tang Zhou Liuliu Ding Lu Fang Department of chemistry Tongji University

ISBN: (纸本)9783037856079

The nanostructured ZnS, CdS/CdCO3 and MnCO3 were prepared by the hydrothermal method with gravity field of 1000 /g in the oil/water system at 100-150℃ for 0.5h. The products were characterized by field-emission scanning electron microscopy （FE-SEM）, transmission electron microscopy （TEM）, powder X-ray diffraction （XRD） and BET method. The results showed that the ZnS samples obtained using ZnCl2 and Na2S2O3 as precursors at 100-120℃ for 0.5h were the polycrystalline microspheres self-assembled by the crystallites with the size of 3-25nm. The pore volume of polycrystalline microspheres decreased with the increase of the size of the applied gravity forces. The morphology of CdS/CdCO3 samples obtained at 100℃ for 0.5h was the flower-like structure, while the as-prepared samples at 120℃ for 0.5h were the nano-ceramic microspheres in shape. The gravity force favors the formation of CdS/CdCO3 samples. Moreover, the MnCO3 polycrystalline flake can be obtained at 100-120℃ for 0.5h under gravity field of 1000 /g.

关键词： Hydrothermal gravity field ZnS CdS/CdCO3 MnCO3 .

来源： cnki会议评论

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cnki会议

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Applied Mathematics and Mechanics(English Edition) 2020年第5期41卷 819-832页

作者： S.M.SAID Department of Mathematics Faculty of ScienceZagazig UniversityZagazig 44519Egypt Department of Mathematics Faculty of Science and ArtsQassim UniversityBuridah 51931Al-mithnabKingdom of Saudi Arabia

The basic equations for a homogeneous and isotropic thermo-magnetoviscoelastic medium are formulated based on three different theories, i.e., the GreenLindsay(G-L) theory, the coupled(CD) theory, and the Lord-Shulman(L-S) theory. The variable thermal conductivity is considered as a linear function of the temperature. Using suitable non-dimensional variables, these basic equations are solved via the eigenvalue approach. The medium is initially assumed to be stress-free and subject to a thermal shock.The numerical results reveal that the viscosity, the two-temperature parameter, the gravity term, and the magnetic field significantly influence the distribution of the physical quantities of the thermoelastic medium.

关键词： eigenvalue approach variable thermal conductivity thermo-viscoelastic gravity field

Determination of the height of Mount Everest using the shallow layer method

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Geodesy and Geodynamics 2021年第4期12卷 258-265页

作者： Youchao Xie Wenbin Shen Jiancheng Han Xiaole Deng School of Geodesy and Geomatics Wuhan UniversityWuhan430079China State Key Laboratory of Information Engineering in Surveying Mapping and Remote SensingWuhan UniversityWuhan430079China Institute of Geophysics China Earthquake AdministrationBeijing100081China Department of Earth and Space Sciences Southern University of Science and TechnologyShenzhen518055China

Shallow layer method(SLM)based on the definition of the geoid can determine the gravity field inside the shallow layer.In this study,the orthometric height of Mount Everest(HME)is calculated based on SLM,in which the key is to construct the shallow layer model.The top and bottom boundaries of the shallow layer model are the natural surface of the Earth and the surface at a certain depth below the reference geoid,respectively.The model-combined strategies to determine the geoid undulation(N)based on SLM are applied to calculate the HME by two approaches:(1)direct calculation by combining N and geodetic height(h);(2)calculation by the segment summation approach(SSA)using the gravity field inside the shallow layer.On December 8,2020,the Chinese and Nepalese governments announced an authoritative value of 8848.86 m,which is referred to a geoid determined by the International Height Reference System(IHRS)(i.e.,the geopotential is 62636853.4 m^(2) s^(-2)).Here,our results(combined strategies(1)EGM2008 and CRUST1.0,(2)EGM2008 and CRUST2.0,(3)EIGEN-6 C4 and CRUST1.0,and(4)EIGEN-6 C4 and CRUST2.0)are referred to the geoid defined by WGS84(i.e.,the geopotential is 62636851.7 m^(2) s^(-2)).The differences between our results and the authoritative value(8848.86 m)are 0.448 m,-0.009 m,-0.295 m,and -0.741 m by the first approach,and 0.539 m,0.083 m,-0.214 m,and -0.647 m by the second approach.When the reference surface WGS84 geoid is converted to the IHRS geoid,the differences are 0.620 m,0.163 m,-0.123 m,and -0.569 m by the first approach,and0.711 m,0.225 m,-0.042 m,and -0.475 m by the second approach.

关键词： Mount everest Orthometric height Shallow layer method gravity field Crust model

Propagation of crust deformation anomalies related to the Menyuan M_(S) 6.9 earthquake

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Earthquake Research Advances 2023年第4期3卷 43-48页

作者： Anfu Niu Chong Yue Zhengyi Yuan Jing Zhao Wei Yan Yuan Li China Earthquake Networks Center Beijing100045China The First Monitoring and Application Center Tianjin300180China

Decoding the variation laws of the deformation field before strong earthquakes has long been recognized as an essential issue in earthquake prediction research. In this paper, the temporal and spatial distribution characteristics of deformation anomalies in the northeastern margin of the Qinghai-Tibetan Plateau before and after the Menyuan M_(S)6.9 earthquake were studied by using the Fisher statistical test method. By analyzing the characteristics of these anomalies, we found that: 1) The deformation anomalies are mainly distributed in the marginal front area of the Qinghai-Tibetan Plateau, where short-term deformation anomalies are prone to occur due to a high gradient of gravity;2) The deformation anomalies along the northeastern margin of the Qinghai-Tibetan Plateau are characterized by spatial propagation, and the migration rate is about 2.4 km/d. The propagation pattern is counterclockwise, consistent with the migration direction of M_(S)≥ 6.0 earthquakes;3) The time and location of the Menyuan earthquake are related to the group migration of earthquakes with M_(S)≥ 6.0. Finally,based on the results of gravity field variation and the theory of crust stress wave, the law of deformation anomaly distribution was discussed. We suggest that both the deformation propagation along the northeastern margin of the Qinghai-Tibetan Plateau and the earthquake migration are possibly associated with the variation of the stress field caused by subsurface mass flow.

关键词： Northeastern margin of Qinghai-Tibetan Plateau Menyuan M_(S)6.9 earthquake Deformation propagation Earthquake migration gravity field

Dynamic changes of gravity fields before and after the 2008 Wenchuan earthquake(Ms8.0)

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Geodesy and Geodynamics 2012年第3期3卷 1-16页

作者： Shen Chongyang Li Hui Sun Wenke Huang Jinshui Sun Shaoan Xuan Songbai Tan Hongbo Liu Shaoming Key Laboratory of Earthquake Geodesy Institute of Seismology China Earthquake Administration Wuhan 430071 China Wuhan Base of Institute of Crustal Dynamics China Earthwuake Adainitration Wuhan 430071 China Graduate University of Chinese Academy of Sciences Beijing 100049 China University of Science and Technology of China Hefei 230026 China

The pattern evolution and dynamic mechanism of the dynamic changes of regional gravity fields occurring before and after the Wenchuan Ms8.0 earthquake are analyzed, based on five epochs of 1998 -2007 mobile gravity data from the middle-south section of the north-south seismic belt, and two epochs of field research data collected after the 2008 Wenchuan earthquake in combination with GPS data, leveling observations, and geotectonic environment data. The regional dynamic gravity changes demonstrate the effects of the eastward flow of solid matter in the Qinghai-Tibetan plateau and the preparation of the 2008 Wenchuan earthquake （2- 10 yr）. The two most meaningful gravity indicators of the Wcnchuan earthquake preparation are the positive （increasing） gravity changes occurring over many years in the southwest epicenter and the largescale gradient zone of gravity variation, with the cumulative difference between the two sides of the gradient zone of gravity exceeding 200 μGal. The positive gravity changes may facilitate a constant energy accumulation and the gradient belt may support seismic shear breakage. Overall, the gravity changes associated with the earthquake preparation indicate a pattern of accelerating increase-decelerating increase-earthquake occurrence. The Songpan-Ganzi block generally displays a negative gravity change, providing evidence for a local upwarp- ing of the deep crust-mantle and an interior expansion of the deep crust attributable to high temperatures. The viewpoint is consistent with the dilatant mechanism for earthquake preparation.

关键词： Wenchuan earthquake gravity field dynamic changes mechanism of earthquake preparation post-earthquake