New high‐resolution grid of gravimetric terrain corrections over Australia

A 9 arc‐second grid of gravimetric terrain corrections has been computed over Australia using ver.2 of the GEODATA 9 arc‐second digital elevation model (DEM) and the fast Fourier transform technique. This supersedes the 27 arc‐second grid previously reported in this journal, computed from ver.1 GEODATA DEM. The improved resolution is possible because of the removal of errors in ver.1 DEM.     

基于数字高程模型的中国岩溶地貌研究进展及前景分析

数字高程模型（DEM）蕴含丰富的地形地貌信息,基于DEM的数字地形分析方法为岩溶地貌研究提供了科学、有效的技术手段。文章针对前人应用DEM研究中国岩溶地貌所涉及的关键技术方法,从岩溶地貌识别的尺度效应、岩溶地貌的识别与分类、岩溶地貌的形态及格局分析、岩溶区生态环境变化等方面进行了梳理和分析,提出未来应构建科学的岩溶地貌数字分类体系,对岩溶地貌进行多尺度、深层次的地形分析和定量表达,并从地形现状研究拓展到地形演变的过程与机理研究,发掘出DEM在岩溶地貌研究中更多的应用。     

多尺度数字高程模型

以岩土工程边坡数值模拟仿真可视化为研究对象,分析、研究了数字高程模型(DEM)和样条函数。将非均匀B样条曲面拟合和准均匀B样条小波多尺度分解结合起来,实现多尺度DEM地形建模方法,设计了相应的算法。实验结果表明,其建模造型效果逼真,多尺度分辨率明显,是一种高效实用的建模方法。     

Evaluation of intermediate TanDEM-X digital elevation data products over Tasmania using other digital elevation models and accurate heights from the Australian National Gravity Database

The successful operation of the TanDEM-X satellite mission is the start of a new era of globally consistent and accurate digital elevation data for planet Earth. In this work available 12 m-resolution intermediate TanDEM-X products (DEM: digital elevation model; HEM: height error map; COV: coverage map; WAM: water indication mask) are evaluated over Tasmania. Elevations from the TanDEM-X intermediate digital elevation model (IDEM) are compared with (a) other global DEMs (30 m-resolution SRTM1 USGS v3 and 30 m-resolution Advanced Spaceborne Thermal Emission Reflectometer (ASTER GDEM2), (b) the local 25 m-resolution DEM made available by Tasmanian environmental authority (DPIPWE), and (c) over 15 000 accurate ground-control-points (GCPs) from the Australian National Gravity Database (ANGD). The comparison with ASTER and SRTM over the area of Tasmania involves over 500 million valid TanDEM-X IDEM elevations. The root-mean-square (RMS) of 8.8 m indicates a reasonable to good agreement of TanDEM-X IDEM and SRTM, while ASTER shows almost twice the disagreement in terms of RMS (～16.5 m). Both, ASTER and SRTM show a (mean) offset of –1.9 m and –2.3 m w.r.t. TanDEM-X IDEM, respectively. By comparisons with GCPs, we find that SRTM and ASTER overestimate the terrain height. The comparison with the AGND GCPs also allows an estimate of the absolute accuracy of the IDEM, which is found to be superior to that of SRTM or ASTER. The RMS error of 6.6 m shows that the IDEM is close to the officially denoted 4 m absolute vertical accuracy considering that the GCPs are not error free. The height error map information layer is found to a suitable first indicator of the (local) accuracy of the IDEM in a relative sense. However, we find that the HEM tends to underestimate observed differences to the GCPs. Terrain-type analyses reveal that the TanDEM-X IDEM is a very consistent elevation database over Tasmania. In conclusion, our study demonstrates that the new TanDEM-X elevation data sets provide improved high-resolution terrain information over Tasmania and beyond.     

一种基于傅里叶变换的去假频内插方法及应用

道间插值方法在地震资料处理中具有十分重要的作用,而地震道空间内插所面临的主要问题是空间假频。基于对模型数据的二维谱特征分析,通过在频率-波数域进行简单的除法运算构造内插算子,给出了一种基于傅里叶变换的地震道空间内插方法,实现了去假频道间插值,并将其应用于垂直地震剖面(VSP)记录的空间内插,取得了满意的效果。由于该方法不需求解线性方程组,可使用快速傅里叶变换,因此具有简单、快速的特点。     

重力及其梯度异常正演的Moving-footprint大尺度模型分解方法

重力及其梯度异常正演计算效率决定了反演的可行性,也是高效构建足量、多样深度学习样本数据的基础。为了进一步提高重力及其梯度异常正演的计算速度,受航空电磁领域"Moving-footprint"快速正演技术的启发,本文在基于网格点几何格架函数空间域快速正演的基础上,提出了一种"Moving-footprint"大尺度模型分解的重力及其梯度异常正演计算方法。此方法在地下半空间内选择观测点正下方一定有效范围的子空间,该观测点异常近似为其对应子空间内长方体单元的异常和,而忽略子空间外长方体单元产生的异常;当观测点移动,其对应的子空间随之移动,从而可以将地下半空间长方体模型进行大尺度模型分解,为每一个计算点所对应的子空间进行正演计算。模型实验表明,在256x256x15个长方体模型的地下半空间内选取32x32x15的子空间进行计算,重力异常及部分梯度异常的相对平均误差小于10%,计算速度提高19倍;文中方法针对1024x1024x15个长方体模型计算时间约为32min,相比已有算法中存在的超常规计算量的瓶颈问题具有显著的计算优势。     

四种南极数字高程模型的精度比较与分析

南极数字高程模型（DEM）是南极冰盖研究的基础数据,目前国际通用的全南极DEM数据主要有JLB97 DEM、RAMPv2 DEM、ICESat DEM以及Bamber 1km DEM. 利用DEM对DEM验证的方式对四种DEM的精度进行比较分析. 结果表明：Bamber 1km DEM和ICESat DEM之间的高程差异最小,平均高程差小于1.8 m,二者均有较高的可靠性. RAMPv2 DEM与Bamber 1km DEM的高程差大于1.9 m,在81.5° S以南和坡度较大的区域,高程差异更为明显,高程可靠性较低. JLB97 DEM与上述三种DEM的偏差超过10 m,高程可靠性最低.     

Shallow landslide hazard assessment using a physically based model and digital elevation data

 A model for the analysis of topographic influence on shallow landslide initiation is applied to an experimental mountain basin where high-resolution digital elevation data are available: the Cordon catchment (5 km²) located in northern Italy. The model delineates those areas most prone to shallow landsliding due to surface topographic effects on hydrologic response. The model is composed of two parts: a steady-state model for shallow sub-surface runoff and an infinite-slope Coulomb failure model which assumes that the soil is cohesionless at failure. An inventory of landslide scars is used to document sites of instability and to provide a test of model performance by comparing observed landslide locations with model predictions. The model reproduces the observed distribution of landslide locations in a consistent way, although spatial variations in soil strength and transmissivity, which are not accounted for in the model, influence specific distribution of landslide areas within regions of similar topographic control. Received: 15 October 1996 · Accepted: 25 June 1997     

处理DEM中闭合洼地和平坦区域的一种新方法

数字高程模型(DEM)中的闭合洼地和平坦区域影响着流域排水网络的自动提取.目前已提出很多方法来处理这两种地形,但均针对已经形成的DEM单元网格进行处理,结果往往生成伪河道及平行河道.在回顾分析了这些方法存在的问题后,提出了一种新的处理方法,该法认为DEM中的闭合洼地和平坦区域是由于低质量的资料输入、生成DEM时的内插误差等引起的.通过增加输入地形高程信息,避免了DEM中平坦区域和闭合洼地的生成,从而使由DEM生成的河网与实际河网能够精确拟合.实例分析表明,该方法效果明显.     

基于ICESat数据的南极冰盖DEM插值方法比较及精度分析

南极数字高程模型(DEM)是从事南极地学和环境变化研究的基础. 内插是建立数字高程模型的重要技术点, 插值方法有多种, 根据不同的适用情况, 不同的插值方法各有优劣. 利用克里格、 距离反权、 三角网剖分、 最小曲率以及移动平均5种插值方法分别建立南极冰盖小范围区域的DEM, 通过抽取部分观测数据作为验证值对各插值方法进行了比较. 结果表明: 克里格插值方法的可靠性最好, 稳定性最高. 然后, 利用克里格插值方法, 基于ICESat测高卫星的GLA12数据建立了南极冰盖的DEM. 由于南极大陆实测数据有限, 缺乏对DEM的检核. 为了分析所建DEM的可靠性, 利用中国南极内陆冰盖考察所采集的GPS实测数据, 对所建立的DEM进行了验证分析. 结果显示, DEM在坡度较缓的南极内陆冰盖区域精度较高, 符合度在3 m以内; 距离卫星轨道越近的区域精度越高, 可达到1 m 以内. 在坡度较大, 高程变化较为显著的区域如沿海地区, 精度较低, 差距最大的点超过40 m.     

Description and release of Australian gravity field model testing data

Gravimetric geoid and/or quasigeoid models are routinely evaluated using co-located GPS-levelling and/or astrogeodetic vertical deflections, globally and regionally. This short note describes these ground-truth data for Australia as of August 2017, which are provided as Electronic Supplementary Material. We provide ～7500 GPS-derived ellipsoidal heights, normal-orthometric heights from the 1971 adjustment of the Australian Height Datum, normal heights from a readjustment of levelling constrained to a model of the ocean's mean dynamic topography, and ～1000 historical astrogeodetic vertical deflections. Updates to these data will be posted on the Intergovernmental Committee on Surveying and Mapping GitHub repository (https://github.com/icsm-au), together with a readme.txt file describing them.     

三度体球冠模型重力异常计算方法及其重力归一化总梯度场特征

提出利用铅垂柱体薄片作为面元的面元积分法,计算三度体球冠重力异常的计算公式,用三度体球冠模型模拟三度背斜体,计算了均匀密度球冠模型、非均匀密度储油球冠模型的重力异常。最后通过误差分析,验证了该方法的可行性。采用波数域重力归一化总梯度计算方法,计算了均匀密度球冠模型、非均匀密度储油气球冠模型G^H场,发现似三度背斜体与二度背斜体有相似的G^H场等值线特征,似三度贮油气藏背斜构造的G^H场亦表现出明显的“两高夹一低”的储油典型标志。所以,可以用非均匀密度三度体储油球冠模型模拟三度贮油气藏背斜构造。     

Dynamic displacement and stress solutions for viscoelastic half‐spaces subjected to harmonic concentrated loads using the Radon and Fourier transforms

In this article a numerical solution for a three‐dimensional isotropic, viscoelastic half‐space subjected to concentrated surface stress loadings is synthesized with the aid of the Radon and Fourier integral transforms. Dynamic displacement and stress fields are computed for points at the surface and inside the domain. The analysis is performed in the frequency domain. Viscoelastic effects are incorporated by means of the elastic–viscoelastic correspondence principle. The equations of motion are solved in the Radon–Fourier transformed domain. Inverse transformations to the physical domain are accomplished numerically. The scheme used to perform the numerical inverse transformations is addressed. The solution is validated by comparison with results available in the literature. A set of original dynamic displacement and stress solutions for points within the half‐space is presented. Copyright © 2009 John Wiley & Sons, Ltd.     

重力流主导的深水沉积特征及其模式——以共和盆地下三叠统为例

深水沉积具有良好的油气勘探前景,近年来已成为沉积学研究的前缘和油气工业界关注的焦点。以共和盆地下三叠统为例,通过野外剖面的详细观察描述,结合室内镜下薄片鉴定与粒度分析,对深水沉积类型、沉积特征、垂向组合、成因机制以及沉积模式进行系统研究。共和盆地早三叠世深水沉积类型主要有滑塌型深水重力流沉积、底流沉积以及深水悬浮沉积,其中滑塌型深水重力流沉积又可识别出滑塌沉积、砂质碎屑流沉积与浊流沉积三种类型。滑塌沉积常见以同沉积褶皱为代表的多种软沉积物变形构造;砂质碎屑流沉积以块状砂岩为主,内部可见砂质团块、泥砾或泥质撕裂屑,块状砂岩顶底与相邻岩层均为突变接触;浊流沉积普遍发育正粒序,可见不完整的鲍马序列,底面常见多种类型的底模构造;底流沉积发育多种牵引流沉积构造。研究区软沉积物变形构造类型丰富,其中滑塌层内的软沉积物变形构造主要在斜坡滑塌过程中形成;未发生滑塌层内的软沉积物变形构造主要因地震使沉积物发生液化作用及流体化作用而形成。在综合分析盆地构造背景、深水沉积分布规律、重力流触发机制的基础上,建立了共和盆地早三叠世滑塌型重力流主导的深水沉积模式。滑塌型重力流主要由地震以及火山事件触发,水道化的地...     

基于数字矿床模型的新疆可可托海3号脉 三维定位定量研究

以数字矿床为手段,进行资源三维定位、定量研究是危机矿山隐伏矿体找矿的新思路和新方法。在对可可托海3号伟晶岩脉的地质模型、成矿规律进行研究和总结的基础上,以Mincromine软件为平台建立了3号脉9个共生结构带的三维实体模型,并利用钻孔数据开展隐伏矿体的定位定量研究。结果表明。可可托海3号脉仍有较好的开发利用潜力,矿体中大于工业品住的BeO保有资源量60t,预测资源量63t。可为矿山的复采提供4～5年的资源保证。在矿脉的外围及深部,大于边界品位的BeO远景资源量1118t,Li20大于边界品位的资源量241t,显示3号脉具有良好的深入勘探开发的前景。对实例的研究也表明,基于数字矿床模型的研究方法在危机矿山找矿中具有独特的优势。     

滑塌型深水重力流沉积特征及沉积模式:以渤海湾盆地临南洼陷古近系沙三中亚段为例*

综合运用钻井岩心、测录井等资料,通过岩心观察、薄片鉴定和粒度分析等方法,对渤海湾盆地临南洼陷古近系沙三中亚段深水重力流沉积类型及其沉积特征、沉积模式展开研究。研究表明,临南洼陷沙三中亚段深水重力流沉积主要发育滑塌沉积、碎屑流沉积和浊流沉积3种成因类型。滑塌沉积以包卷层理、液化砂岩脉、阶梯状小断层、变形岩层与未变形岩层叠置为典型特征。碎屑流沉积中砂质碎屑流沉积分布较广,以突变的底部接触面、块状层理、泥岩撕裂屑、土黄色泥砾、突变或不规则的上接触面为典型识别标志。浊流沉积则以正粒序层理、底部冲刷面和槽模、薄层砂泥互层、不完整的鲍马序列为典型识别标志。滑塌沉积主要发育在三角洲前缘斜坡根部,在滑塌沉积前方形成碎屑流沉积,碎屑流向前搬运的过程中,流体被稀释逐渐转化成浊流。滑塌型深水重力流沉积整体分为近源沉积、中部沉积和远源沉积3个部分: 近源沉积主要发育具变形构造的滑塌沉积和厚层块状砂质碎屑流沉积;中部沉积主要发育砂质碎屑流沉积及浊流沉积;远源沉积以薄层浊流沉积为主。     

湖相重力流水道沉积特征与沉积模式:以鄂尔多斯盆地瑶曲铁路桥剖面三叠系延长组为例*

陆相深水重力流水道的类型细分及其沉积模式是制约其油气勘探开发的重要因素,但研究程度低。通过对鄂尔多斯盆地南缘瑶曲铁路桥剖面三叠系延长组实测、水道形态参数统计及岩相、粒度等分析,开展了湖相重力流水道的沉积特征、沉积过程及沉积模式研究。结果表明:(1)研究区内可识别出4期复合水道,主要为洪水重力流成因。根据其内部单一水道及单砂体形态特征、岩相组成,将其细分为沉积型和过渡型两类。(2)剖面下部2期复合水道为沉积型,以悬浮载荷成因岩相为主,常见块状净细砂岩、薄层泥岩岩相组合和鲍马序列岩相组合;上部2期复合水道为过渡型,岩相以底床载荷与悬浮载荷共存为特征,自下而上以交错层理细砂岩或叠瓦状泥砾细砂岩与含泥砾/泥岩撕裂屑块状细砂岩、平行层理粗粉砂岩及薄层泥岩的岩相组合为特征。(3)结合单一水道规模及其相互关系,建立了区内过渡、沉积型重力流水道的半定量沉积模式。过渡型水道内部侵蚀与沉积作用共存,单一水道宽度小、宽厚比低,呈透镜状,水道间切割性强,砂体横向稳定性较低,表现出不定向叠加、侧向拼接样式;沉积型水道内部由沉积作用主导,单一水道宽度较大、宽厚比较高,呈似板状—透镜状,砂体横向稳定性较高,表现出稳定的垂向加积样式。     

Simulation of the interactions between gravity processes and contour currents on the Algarve Margin (South Portugal) using the stratigraphic forward model Sedsim

The margin of the Gulf of Cadiz is swept by an intermediate current the Mediterranean Outflow Water (MOW) flowing from the Mediterranean to the Atlantic. On the northern margin of the Gulf (Algarve Margin, South Portugal) the MOW intensity is low, and fine-grained contourite drifts are built up with an alongslope alignment. Recent sedimentological studies emphasize the presence of complex process interactions resulting in the formation of a unique depositional architecture. Alongslope processes related to contour currents generate contourite drift, while downslope processes form canyons and channels aligned on deep faults. This paper uses a combined oceanographic and geological dataset to simulate the different types of interactions between gravity processes and contour currents, which were evidenced on this margin. An extrapolation of the contour current intensity has been used based on the present day velocity field and sea-level fluctuations over the simulated geological time-scale. According to our model results, the construction of the contourite drift is closely linked to contour current velocities and directions, the types of sediments transported and the existing topography. Using modern sedimentological understanding of the area, we have correlated gravity flow's strongest activity to sea level lowstand periods mainly due to a closer connection between canyon's mouth and river or deltaic systems. The simulated gravity flows are initialized at different locations and times on the margin depending on the preserved lobes retrieved from seismic analysis. Their resulting morphological features are identified as perched-lobes with volumes and forms close to the ones observed on Portimão and Lagos Drifts. This study provides a process-based understanding of the construction of contourite system and a physical evaluation of the interactions between gravity flows perpendicular to the slope, and alongslope processes. In addition, it shows the influence of autocyclic factors in the construction of contourite sedimentation, which is important to consider in future sedimentary paleo-reconstruction interpretations.