Recent Process in Near-Space Gravity Wave Analysis Based on Satellite Measurements

This article focused on the research progress in the gravity wave analysis based on satellite measurements including MODIS, AIRS, AMSU, MLS, DNB, COSMIC,HIRDLS and SOFIE. Besides, a few ground-based observation results and numerical models were briefly introduced and some cases of joint applications of satellite observations with ground-based observations and numerical models in the gravity waves were listed. In general, the satellite remote sensing data play an important role in the study of the characteristics in near-space environment, which can be applied to analyze the scales of gravity waves induced by different sources, correlations between the instabilities and waves as well as their patterns, the impacts in the climate process, wave-wave interactions and wave-flow interactions with other data.     

二代小波变换在重力场源分离中的应用

野外采集的重力数据是地下各类地质体重力场的叠加反映,如何有效地分离深源场和浅源场是重力资料处理中的一项重要内容。基于二代小波变换基本理论,在一维的基础上,给出了二维Haar预测算子的构造方法,并利用密度模型正演模拟,证明了二代小波变换实现多尺度分解的有效性,并以苏北某地区重力数据为例,应用二代小波变换开展浅部和深部重力异常场的分离。结果表明,该方法简单实用,在重力数据的场源分离中可以发挥重要的作用,对研究区域性断裂构造特征、划分构造单元、圈定隆坳格局等方面的地质问题具有参考价值。     

我国探月工程可采用的一种月球钻探取样方法的初步分析

美国和前苏联已完成的月球取样方法分别是载人登月取样和地面遥控取样钻机取样。基于美国和前苏联的方法,提出了一种可供我国嫦娥工程选用的月壤钻探取样方案,即用遥控取样钻机,配备硬质合金钻头、空心螺旋钻具,采用振动-回转钻进工艺。在高真空和低重力条件下,可选用空心螺旋钻具来解决排屑和钻压问题。顺利排屑的基本条件为钻具的螺旋升角应小于月壤与钻具之间的摩擦角、钻具的回转速度应大于临界转速。通过分析计算可知在月球上采用外螺旋钻具时,临界转速比在地球上要小得多,因此在获得同样的回转力矩条件下可匹配较小功率的电动机。     

Contribution of gravity and magnetic data in delineating the subsurface structure of Hammam Faroun area, Gulf of Suez, Egypt

The Hammam Faroun has a particular importance due to its geothermal activity which constitutes the main geothermal resource of Egypt. The area is located on the Sinai Peninsula, a subplate bounded by two seismically active structural zones along the Gulf of Suez and Gulf of Aqaba. High-resolution ground-based gravity and magnetic data are available for the entire Hammam Faroun area, acquired as part of a national project to explore for mineral, geothermal, and hydrocarbon resources. Gravity and magnetic data were analyzed using Source Edge Detection and Source Parameter Imaging (SPI) techniques to image subsurface structures. These analyses show that the area is characterized by a set of northwest-striking faults lying parallel to the Gulf of Suez. Orthogonal patterns are also present, possibly related to rifting of the Gulf of Suez. Depth analysis using the SPI method indicates that surface faults extend to 5-km depth. Analysis of potential-field data elucidates the structurally complex subsurface structure of the Hammam Faroun area.     

月球质量瘤成因及研究方法综述

月球重力探测一直是国际深空探测的重要目标之一。计算月球重力发现,月球表面存在重力异常区域——质量瘤。通过对质量瘤的特征、成因以及研究方法进行概述总结,认为质量瘤是月幔隆升、高密度物质聚集所致,后期的玄武岩充填可能会增加重力异常,但作用微弱。尽管可以利用月震波分析和月球内部三维密度分布反演新技术,但是基于重力数据和地形资料的研究方法更能高效地对月球的重力场及其特征进行详细研究,高精度的重力场模型可以揭示月球深部构造及层圈形态,进而探索早期月球起源、内部物质演化与运动过程等。该研究方法可为月球和其他类地行星的重力研究提供参考。     

Noise-Dependent Adaption of the Wiener Filter for the GPS Position Time Series

Various methods have been used to model the time-varying curves within the global positioning system (GPS) position time series. However, very few consider the level of noise a priori before the seasonal curves are estimated. This study is the first to consider the Wiener filter (WF), already used in geodesy to denoise gravity records, to model the seasonal signals in the GPS position time series. To model the time-varying part of the signal, a first-order autoregressive process is employed. The WF is then adapted to the noise level of the data to model only those time variabilities which are significant. Synthetic and real GPS data is used to demonstrate that this variation of the WF leaves the underlying noise properties intact and provides optimal modeling of seasonal signals. This methodology is referred to as the adaptive WF (AWF) and is both easy to implement and fast, due to the use of the fast Fourier transform method.

     

基于三维激光扫描的空间地物建模

利用地面三维激光扫描仪获取的空间数据,进行了三维空间地物建模研究。以建筑物建模为例,首先从原始数据中分离提取建筑物,然后对得到的建筑物数据进行去噪处理,再通过整体匹配纠正并对原始测量数据进行重新采样和拼接配准,建立了由三角网构成的三维表面模型。结果表明,所构建的三维表面模型较好地表达了建筑物的几何特征,户外实验也验证了上述过程可以实现对建筑物快速三维建模。     

Application of the non-seismic geophysical method in the deep geological structure study of Benxi-Huanren area

Based upon 1:200,000 regional gravity and aeromagnetic data, gravity and aeromagnetic slice maps were obtained through fast Fourier transformation (FFT) upward continuation. A comparison between gravity and aeromagnetic slice maps at different depths combined with regional geological data and Magneto-Telluric sounding reveals the deep geological structure of Benxi-Huanren area and provides important information for study of the deep geological evolution process of Benxi-Huanren area. Yanshanian granitic pluton is widely distributed in this area and tends to be continuous toward depth. Significant metallogenic areas, such as Dataigou and Nanfen areas, lie above the buried granitic pluton. The Paleoproterozoic strata distribution area and the Archean strata distribution area have similar characteristics in terms of gravity anomaly. The iron-bearing formation in Anshan area is Archean supracrustal rock which was not engulfed by Archean granite. The thickness of Liaoji paleo-rift can be up to 10 km, whose lower part was intruded by Yanshanian granites. The basement of the Liaoji rift was remelted during granite intrusion in Yanshanian period.     

冰川均衡调整重力与径向位移近似关系的不确定性

根据不同地幔粘滞度的冰川均衡调整(glacial isostatic adjustment, GIA)模型, 研究了地球内部各个圈层对GIA粘性重力扰动速率的贡献, 检验了粘性重力扰动速率与径向位移速率的近似关系及其是否独立于地幔粘滞度, 同时利用绝对重力和GPS(global positioning system)径向位移数据从实测角度对Wahr的近似关系进行比较和验证.结果表明: 岩石圈对GIA重力扰动速率和大地水准面异常速率的贡献都超过了86%, 而岩石圈以下5个圈层的总贡献不大于14%;利用近似关系, 由重力信号转换的径向位移速率与有限元模拟的结果相对差异大约为15%, 且相对差异的大小不依赖于地幔粘滞度的变化; 根据北美绝对重力和GPS径向位移数据得到实测的粘性重力-径向位移比值为0.141±0.014 μGal/mm, 与Wahr的理论值(0.154 μGal/mm)非常接近, 相对差异仅为9.2%.因此, 定量给出了粘性重力-径向位移近似关系的不确定性为9.2%~15.0%, 为利用此近似关系分离GIA和现今地表质量变化粘弹信号的不确定性估计提供了重要参考.      

曲波变换在位场信号提取中的应用研究

为了重磁数据中有效信号的分离与提取,本文研究了最近十几年发展起来的一种方法:曲波变换方法(Cur-velet transform method).从曲波变换的基本原理入手,通过重力位场理论模型数据分析了曲波变换的多尺度分解重构能力,并且利用加噪理论模型数据分析了曲波变换的阈值去噪能力,此外,还使用曲波变换对南岭东部地区...     

High-resolution regional gravity field model of Pakistan based on best residual terrain model (RTM) of topography and interpolation techniques

This study focuses on the development of absolute gravity model for Pakistan based on best possible residual terrain model of gravity using residual terrain modeling technique. The datasets used for the development of model are observed gravity, global gravity models, and Shuttle Radar Topographic Mission (SRTM30) elevation data. The residual terrain modeling technique has been used in the remove-restore procedure for smoothing the observed gravity field. Different topographic elevation models were tested in the model selection and one best possible model with minimum mean and standard deviation was selected for residual terrain effects. Least square collocation technique has been used for quality control and error estimates. The best possible covariance model was established from residual gravity for onward prediction of gravity anomalies at the earth surface for error and prediction analysis. The residual terrain effect of gravity, value of free air anomaly from EGM96, and observed free air anomaly are added to normal gravity to compute the absolute gravity at earth surface. The prediction of these parameters is made by employing Lagrange interpolation with least square adjustment. The results are compared with ～5% randomly selected data points not utilized for the development of covariance function and/or model development. Spline interpolation technique has also been used for the prediction of gravity field-related parameters. Lagrange interpolation exhibits relatively superior results over spline-based interpolation. This is as per expectation due to the reason that additional gridding for spline interpolation filters the signal part as well. This fact is evident from the results of spline interpolation of Grid-I and Grid-II with relatively better prediction results in Grid-I. This version of the model is capable of prediction having limiting error of 30 mGal. The predicted results show that 96.16% of prediction data falls within above-mentioned limit with Lagrange interpolation technique with least square adjustment for whole Pakistan area. The adverse effect of gridding is absent in case of Grid-I due to relatively flat areas and predicted data matches totally with control values for both spline as well as Lagrange interpolations. However, in case of Grid-II which includes high mountains of Himalaya, gridding effect is present and the accuracy of the predicted results falls to ～92%. The computed results have been compared with absolute values predicted using EGM96 and EGM2008 models as well. The gravity field recovered with PAKGM model is much better, i.e., ～ 96.16%, than both with EGM96 and EGM2008 which is about 85% only.     

Characteristics of gravity and magnetic fields and deep structural responses in the southern part of the Kyushu-Palau Ridge

The southern part of the Kyushu-Palau Ridge (KPR) is located at the conjunction of the West Philippine Basin, the Parece Vela Basin, the Palau Basin, and the Caroline Basin. This area has extremely complex structures and is critical for the research on the tectonic evolution of marginal seas in the Western Pacific Ocean. However, only few studies have been completed on the southern part, and the geophysical fields and deep structures in this part are not well understood. Given this, this study finely depicts the characteristics of the gravity and magnetic anomalies and extracts information on deep structures in the southern part of the KPR based on the gravity and magnetic data obtained from the 11th expedition of the deep-sea geological survey of the Western Pacific Ocean conducted by the Guangzhou Marine Geological Survey, China Geological Survey using the R/V Haiyangdizhi 6. Furthermore, with the data collected on the water depth, sediment thickness, and multichannel seismic transects as constraints, a 3D density model and Moho depths of the study area were obtained using 3D density inversion. The results are as follows. (1) The gravity and magnetic anomalies in the study area show distinct zoning and segmentation. In detail, the gravity and magnetic anomalies to the south of 11°N of the KPR transition from high-amplitude continuous linear positive anomalies into low-amplitude intermittent linear positive anomalies. In contrast, the gravity and magnetic anomalies to the north of 11°N of the KPR are discontinuous and show alternating positive and negative anomalies. These anomalies can be divided into four sections, of which the separation points correspond well to the locations of deep faults, thus, revealing different field-source attributes and tectonic genesis of the KPR. (2) The Moho depth in the basins in the study area is 6–12 km. The Moho depth in the southern part of KPR show segmentation. Specifically, the depth is 10–12 km to the north of 11°N, 12–14 km from 9.5°N to 11°N, 14–16 km from 8.5°N to 9.5°N, and 16–25 km in the Palau Islands. (3) The KPR is a remnant intra-oceanic arc with the oceanic-crust basement.which shows noticeably discontinuous from north to south in geological structure and is intersected by NEE-trending lithospheric-scale deep faults. With large and deep faults F3 and F1 (the Mindanao fault) as boundaries overall, the southern part of the KPR can be divided into three zones. In detail, the portion to the south of 8.5°N (F3) is a tectonically active zone, the KPR portion between 8.5°N and 11°N is a tectonically active transition zone, and the portion to the north of 11°N is a tectonically inactive zone. (4) The oceanic crust in the KPR is slightly thicker than that in the basins on both sides of the ridge, and it is inferred that the KPR formed from the thickening of the oceanic crust induced by the upwelling of deep magma in the process of rifting of remnant arcs during the Middle Oligocene. In addition, it is inferred that the thick oceanic crust under the Palau Islands is related to the constant upwelling of deep magma induced by the continuous northwestward subduction of the Caroline Plate toward the Palau Trench since the Late Oligocene. This study provides a scientific basis for systematically understanding the crustal attributes, deep structures, and evolution of the KPR.©2021 China Geology Editorial Office.     

重磁3D物性反演技术在金属矿勘探中的应用

解反演问题是地球物理资料处理解释的主要环节.反演就是依据已获得异常特征,结合地质和其他资料,求解地下源体的空间位置、形状及物性特征参数.随着对地质体全方位精细结构研究要求的提高,重磁等反演技术已发展到3D反演阶段.重磁反演主要有两种方法,即形态反演(建立场源模型形态单元)和物性反演(构建物性模型单元).在物性模型构建中...     

地学大断面对区域重力资料解释的意义

为了深化区域重力资料的解释,需要充分利用深地震测深等方法所提供的地壳及其深部资料.近几年我国完成的若干条地学大断面提供了这种可能.我们认为依据它为基础设计的较符合实际情况的重力密度模型,才会得到较为有效的解释结果;如果仅使用少量深地震测深点的资料去换算重力莫霍面是极不可靠的,由此作出的成矿预测也是不会正确的.新的重力模型应该包括地壳的多层结构、断块构造、变密度特征、莫霍面密度不均匀性和起伏不大、断裂产状在深部可能是平缓的剪切带等.而两层结构模型忽视了这些基本特征,解释结果没有实际意义.     

Chasing a complete understanding of the triggering mechanisms of a large rapidly evolving rockslide

Rockslides in alpine areas can reach large volumes and, owing to their position along slopes, can either undergo large and rapid evolution originating large rock avalanches or can decelerate and stabilize. As a consequence, in particular when located within large deep-seated deformations, this type of instability requires accurate observation and monitoring. In this paper, the case study of the La Saxe rockslide (ca. 8 × 10⁶ m³), located within a deep-seated deformation, undergoing a major phase of acceleration in the last decade and exposing the valley bottom to a high risk, is discussed. To reach a more complete understanding of the process, in the last 3 years, an intense investigation program has been developed. Boreholes have been drilled, logged, and instrumented (open-pipe piezometers, borehole wire extensometers, inclinometric casings) to assess the landslide volume, the rate of displacement at depth, and the water pressure. Displacement monitoring has been undertaken with optical targets, a GPS network, a ground-based interferometer, and four differential multi-parametric borehole probes. A clear seasonal acceleration is observed related to snow melting periods. Deep displacements are clearly localized at specific depths. The analysis of the piezometric and snowmelt data and the calibration of a 1D block model allows the forecast of the expected displacements. To this purpose, a 1D pseudo-dynamic visco-plastic approach, based on Perzyna’s theory, has been developed. The viscous nucleus has been assumed to be bi-linear: in one case, irreversible deformations develop uniquely for positive yield function values; in a more general case, visco-plastic deformations develop even for negative values. The model has been calibrated and subsequently validated on a long temporal series of monitoring data, and it seems reliable for simulating the in situ data. A 3D simplified approach is suggested by subdividing the landslide mass into distinct interacting blocks.     

我国重力固体潮实验研究进展

综述了我国重力固体潮研究领域的相关成果,包括积累大量观测数据,建立国际潮汐基准和独立的国际标定系统,利用小参数扰动法发展了地球潮汐理论模型,用计算机演绎法实施潮汐位展开,用残差信号对数据作预处理,用小波分析方法设计滤波器,用远近区结合法解算海潮负荷,用大气重力格林函数法解算气压对重力场观测的影响,测定了地球的近周日自由摆动参数,将固体潮汐研究成果应用于地震和重力测量,对重力仪进行静电反馈改造,精密测定了仪器相位滞后和对超导重力仪进行了标定等内容,讨论了今后研究展望。     

Filtering of the gravimetric anomalies to the study of the geological structures of Oued Zarga (Septentrional Tunisia): structural implications

Gravity data were analysed in the Northern Tunisian Atlas (case study of Oued Zarga area) to better understand the organization of its underlying structures. The gravity data analysis included the construction of a gravity anomaly maps and two and a half dimensional gravity model. The qualitative analysis of gravimetric maps served for the foundation of a new structural map of the study region that constitutes a new contribution of the gravimetry in this present work. In addition, the complete Bouguer and residual gravity anomaly maps indicate a negative gravity anomaly over the Triassic evaporitic outcrops of Jebel Guerouaou and prominent NE?CSW-trending features associated with the boundary of the Triassic rocks and surrounded layers. A NW?CSE-trending gravity model that crosses the Triassic evaporitic outcrop at Jebel Guerouaou can be explained by a deep-rooted salt diapir.     

华南地区地壳厚度变化及对成矿类型的制约:来自卫星重力数据的约束

华南地区是中国金属矿产资源的“大粮仓”,分布有多个多金属成矿带。多金属成矿带的形成常伴随着地下特殊的深部背景和过程,通过莫霍面深度的计算,对华南地区的地壳厚薄变化所反映的壳幔耦合关系进行研究,可为探索华南地区地下巨量金属资源的形成与演变过程提供参考。本文首先基于球坐标的重力解算方法对高阶卫星重力场模型EIGEN-6C4的数据进行校正,得到华南地区的卫星布格重力异常。然后采用改进的Parker-Oldenburg方法进行变密度界面反演,获得华南地区莫霍面起伏特征。最后结合区内不同成矿带的范围和前人发表的地质、地球化学等资料,探讨华南地区不同成矿带的成矿物质来源与莫霍面起伏的关系。认为长江中下游和钦杭东段处于莫霍面隆起区域的成矿带,幔源物质对其成矿作用起主导地位,形成以铜、铁为主的多金属矿床;南岭、武夷、钦杭西段及鄂西—湘西位于莫霍面隆-陷交替区域的成矿带,成矿与壳、幔源物质的相互作用密切相关,最终形成钨、锡、金、银、铅锌等多金属矿床。     

Summer monsoon rainfall scenario over Bangladesh using a high-resolution AGCM

Summer monsoon rainfall was simulated by a global 20 km-mesh atmospheric general circulation model (AGCM), focusing on the changes in the summer monsoon rainfall of Bangladesh. Calibration and validation of AGCM were performed over Bangladesh for generating summer monsoon rainfall scenarios. The model-produced summer monsoon rainfall was calibrated with a ground-based observational data in Bangladesh during the period 1979–2003. The TRMM 3B43 V6 data are also used for understanding the model performance. The AGCM output obtained through validation process made it confident to be used for near future and future summer monsoon rainfall projection in Bangladesh. In the present-day (1979–2003) climate simulations, the high-resolution AGCM produces the summer monsoon rainfall better as a spatial distribution over SAARC region in comparison with TRMM but magnitude may be different. Summer monsoon rainfall projection for Bangladesh was experimentally obtained for near future and future during the period 2015–2034 and 2075–2099, respectively. This work reveals that summer monsoon rainfall simulated by a high-resolution AGCM is not directly applicable to application purpose. However, acceptable performance was obtained in estimating summer monsoon rainfall over Bangladesh after calibration and validation. This study predicts that in near future, summer monsoon rainfall on an average may decrease about ?0.5 % during the period 2015–2034 and future summer monsoon rainfall may increase about 0.4 % during the period 2075–2099.     

东营凹陷沙三中亚段三角洲前缘滑塌型重力流岩相类型及其分布特征

以东营凹陷沙三中亚段三角洲前缘滑塌型重力流砂体为研究对象,利用三维地震、钻井岩心、测录井和分析测试等资料,开展三角洲前缘滑塌型重力流砂体岩相和岩相组合类型划分及分布特征研究。根据泥质含量和沉积构造,划分出13种岩相类型,其中块状层理砂岩相在研究区最为发育。以泥岩、冲刷面或岩相转化面为界,划分出20种岩相组合类型,分为5大类,分别是保留原始沉积构造的岩相组合、变形构造发育的岩相组合、块状层理和碎屑发育的岩相组合、下部碎屑流和上部浊流沉积的岩相组合,以及不完整鲍马序列的岩相组合,反映重力驱动事件中的滑动、滑塌、碎屑流、碎屑流-浊流、浊流沉积作用。根据不同类型重力流的垂向组合和典型剖面岩相分布特征,认为从盆地斜坡到盆地平原,重力流呈现滑动-滑塌-碎屑流-浊流演化特征,滑塌近端主要发育滑动作用岩相组合和滑塌作用岩相组合,滑塌中部主要发育碎屑流岩相组合和碎屑流与浊流过渡转化岩相组合,滑塌远端主要发育浊流作用岩相组合。