DEM分辨率对提取东北地区坡度的影响研究

目前国内外广泛采用的坡度-等效剪切波速关系模型中,坡度主要基于30″分辨率数字高程数据的提取。DEM分辨率对坡度的提取具有重要影响,且对于不同地区、地貌单元的影响不同。本文以我国东北地区1″、3″、30″分辨率DEM为基础,分别提取研究区域内公里网格点的百分比坡度,分析不同分辨率下提取坡度差异的原因。区分平原、丘陵和山地统计分析坡度随分辨率变化特征,通过比较多种拟合模型的拟合优度和坡度分级平均相对差值,给出不同分辨率下的最佳坡度转换关系。研究结果表明,坡度体现计算面积的平均特性,随着分辨率的增大,栅格计算面积减小,导致坡度有所差异,区域坡度变化越大差异越大;在我国东北地区,随着DEM分辨率的降低,坡度-频率分布曲线向低坡度段移动,且均值、方差及值域变小,不同地貌的坡度-频率分布曲线向低坡度方向移动,且峰值区域变窄,其中平原地貌变化趋势性显著,丘陵次之,山地最小;平原及山地地貌最佳坡度拟合为线性拟合,丘陵地貌下1″、3″与30″分辨率下最佳坡度拟合分别为线性拟合和多项式拟合。     

基于遥感特征指数的地表水体自动提取技术研究

为了从海量遥感数据中有效地提取地表水体信息,并提高自动化提取效率,提出了一种基于遥感特征指数的地表水体自动提取方法.该方法选取归一化植被指数(NDVI)、归一化建筑指数(NDBI)和修正归一化水体指数(MNDWI)作为遥感特征指数集,并根据这些指数构建了遥感特征指数曲线.通过分析,发现地表水体在特征曲线中单调上升,植被在特征曲线中单调下降,而其它地物并无此特征.因此,根据这一规律,利用ERDAS IMAGINE软件建立了自动化提取模型.通过与其他方法对比,表明所建立的模型在精度和自动化方面都明显优于其他方法,可用于海量数据地表水体的自动提取.最后,在ARCGIS环境下,并通过决策树模型初步实现了地表水体的自动分类.     

龙门山南段山前天全-乐山剖面磁组构研究及其对新生代构造变形的指示意义

四川盆地西南部西侧为龙门山冲断带,南面紧挨川西南褶皱带,其新生代构造变形特征对于认识青藏高原东南缘的变形机制具有一定的指示意义.磁组构是一种灵敏的应变指示计,在变形微弱的沉积岩地区尤为适用.本文在雅安-乐山剖面选取12个采样点进行磁组构分析,结合已有的天全-雅安飞仙关剖面的27个采样点数据,综合讨论川西南地区的构造变形特征.所有采样点的磁组构测试结果显示出3种弱变形的磁组构类型:沉积磁组构、初始变形磁组构和铅笔状磁组构.雅安-乐山剖面采样点的磁线理绝大部分为北东-南西走向,和龙门山南段的整体延伸方向一致,表明四川盆地西南缘新生代构造变形主要受控于龙门山的构造作用.飞仙关剖面的磁组构测试结果显示44%的采样点表现出磁线理和地层走向斜交的特征,由初始变形磁组构演变而来,并且所有异常磁组构仅局限在断层上盘,本文认为这是雅安地区新生代期间局部逆时针旋转引起变形叠加的结果.     

基于MDT测试资料的储层油水界面自动提取方法研究

通过对MDT地层压力数据以及地层压力梯度线形态的分析,提出了利用三次样条插值函数将有限个数据点的地层压力梯度线进行深度等间距采样,以得到连续分布的地层压力梯度线.在抛物线形式的地层压力梯度线上,油水界面对应于该抛物线的顶点.根据最大值原理可以在地层压力梯度线上提取油藏油水界面深度,利用Fortran语言编制了相应的计算机程序,实现了油藏油水界面自动提取的目的.利用该程序可以减小油田现场处理过程中带入的额外误差,节省操作人员的处理时间,减少工作量.实际应用表明,该方法是可靠的,计算结果完全符合油田储量计算的误差标准,利用其获取的结果真实有效.     

基于无人机影像的辽宁农居建筑物提取技术与应用研究

本研究以实地调研数据为基准,无人机影像数据分析为验证,进行了基于无人机识别能力范畴的辽宁农居建筑结构类型划分,并根据区域结构类型比例、影像特性等指标优化了农居遥感解译标志整体参数,提取了不同建筑结构的不同解译标志阈值区间,并基于无人机低空正射影像DOM、数字表面模型DSM制定改进型DSM提取算法处理流程与代码,利用Python语言及开发环境完成了遥感影像要素提取与评估系统开发应用。通过最优组合解译标志获取无人机影像解译一致性系数Kappa=0.723,表明制定的解译标志特征对获得具有较好一致性的房屋结构类型具备一定的可行性。以改进型DSM提取算法为核心的建筑物提取软件提取建筑的整体精度为75%,基本满足地震应急需求。     

基于开源平台的陕西省地震应急专题图自动生成技术的研究和实现

结合陕西省地震应急对专题图产出的要求,通过研究开源GIS平台,在QGIS和PostGIS中实现地震信息的自动获取、影响场生成和专题图的自动产出,并通过与Docker微服务构架结合构建多服务并行运行框架,最终实现基于开源平台的陕西省地震应急专题图自动产出。经测试显示,该系统提高了地震应急专题图出图效率和运行稳定性,并减少了系统开发和运维的成本。     

一种快速的震害评估方法——基于区域的遥感影像差值分割提取技术研究

根据建筑物在高分辨率遥感影像中“面”的特征,对差值法提取倒塌建筑物技术进行改进,将多阈值分割、类别筛选和数学形态学运算等概念引入差值法后处理过程中,提出基于区域的差值分割提取技术,并将新方法引入到完好建筑物的提取.通过对汶川地震中都江堰市某个街区进行计算,使用改进后的新方法进行评估,并与面向对象的方法和目视判读方法进行...     

兰州庄浪河阶地差分GPS测量与构造变形分析

在综合分析兰州庄浪河河流阶地发育和分布特征的基础上,采用高精度差分GPS对Ⅰ～Ⅲ级阶地进行了详细的测量,获得了庄浪河阶地纵横剖面图.结合不同级别阶地年代学资料研究了其构造变形特征,获得了穿越断裂带地区的阶地变形特点、变形带宽度、变形幅度和速率等定量参数.研究表明:兰州庄浪河阶地构造变形主要表现为断裂扩展褶皱模式,阶地变形速率在晚第四纪以来有逐渐加速的特点.     

黄河中游河流阶地的对比及阶地系列形成中构造作用的多层次性分析

黄河在流经青藏市原东北缘海原－同以弧形构造区的过程中,发育了多达10－21组的斯座和侵蚀型阶地,其最大拔河高度为40lm,最高阶地的发育年代为1．57MaBP。通过对该区米家山、车木峡和黑山峡河口3处黄河阶地以及我国北方大范围内河流阶地的对比分析发现,河流阶地系列形成中在构造作用上具有多层次性特征,即它包含了不同范围或规模和不同级次构造隆升作用所导致的阶地。研究区的黄河阶地系列可以划分为3个层次。其中,第一层次的阶地共有6级,为我国北方大范围内同期形成的阶地,它们代表1．6Ma以来青藏高原阶段性隆升的次数,其隆升幅度由西向东逐渐减小;第二层次的阶地共有5级,为海原－天景山构造区内同期发育的阶地,它们代表1．6Ma以来该构造区本身自隆升的次数和幅度;第三层次阶地为发育在米家山东坡的10级不同期阶地,它们代表1．6Ma以来海原构造山地独自的抬升的次数和幅度。阶地发育时间与黄土－古土壤序列的对比还表明,反映青藏高原大范围构造隆升的第一层次阶地与气候变化之间有很好的可对比性,其形成年代均与相应古土壤发育时间的间冰期对应,暗示导致河流下切的在范围构造抬升与强干冷期后同样可导致河流下切的气候暖湿期紧密相关,它们共同组成了构造－气候旋回。第二层次和第三层次阶地的形成时间与气候变化之间无统一特定的关系,显示它们的形成更主要的受控于天景山块体和海原构造带的隆升作用。因此,研究区的河流阶地主要可分为2种成因类型。一种是在大范围构造抬升和气候变化联合作用下形成的构造－气候旋回阶地,此类阶地分布范围广,具有区域间的可对比性;另一种是以局部构造抬升为主导因素形成的脉动式构造旋回阶地,此类阶地的分布受 控于活动构造带,在构造区带内自成体系,不具有区域间的可对比性。     

Comparison of River Terraces in the Middle Reach Valleys of the Yellow River and Analysis on the Multi-Gradational Features of Tectonism in the Formation of Terrace Series

Where the Yellow River flows through the Haiyuan-Tongxin arc-form tectonic region on the northeastern side of the Qinghai-Xizang (Tibet) Plateau, as many as 10～21 basis and erosion terraces have been produced, among which the biggest altitude above river level is 401m and the formation age of the highest terrace is 1.57 Ma B.P. Based on comparative analysis of the Yellow River terraces located separately in the Mijiashan mountain, the Chemuxia gorge, the Heishanxia gorge and the other river terraces in the vast extent of the northern part of China, it has been found that the tectonic processes resulting in the formation of the terrace series is one of multi-gradational features, i.e., a terrace series can include the various terraces produced by tectonic uplifts of different scopes or scales and different ranks. The Yellow River terrace series in the study region can be divided into three grades. Among them, in the first grade there are 6 terraces which were formed separately at the same time in the vast extent of the northern part of China and represent the number and magnitude of uplift of the Qinghai-Xizang Plateau since 1.6 Ma B. P. ; in the second grade there are 5 terraces which were separately and simultaneously developed within the Haiyuan-Tianjingshan tectonic region and represent the number and magnitude of uplift of this tectonic region itself since 1.6Ma B. P.; in the third grade there are 10 terraces which developed on the eastern slope of the Mijiashan mountain and represent the number and amplitude of uplift of the Haiyuan tectonic belt itself since 1.6Ma B.P. Comparison of the terrace ages with loess-paleosoil sequence has also showed that the first grade terraces reflecting the vast scope uplifts of the Qinghai-Xizang Plateau are very comparable with climatic changes and their formation ages all correspond to the interglacial epochs during which paleosoils were formed. This implies that the vast extent tectonic uplifts resulting in river down-cutting are closely related to the warm-humid climatic periods which can also resnit in river downward erosion after strong dry and cold climatic periods, and they have jointly formed the tectonic-climatic cycles. There exists no unanimous and specific relationship between the formation ages of the second and third grade terraces and climatic changes and it is shown that the formation of those terraces was most mainly controlled by tectonic uplifts of the Tianjingshan block and the Haiyuan belt. The river terraces in the study region, therefore, may belong to 2 kinds of formation cause. One is a tectonic-climatic cyclical terrace produced jointly by vast extent tectonic uplifts and climatic changes, and the terraces of this kind are extensively distributed and can be well compared with each other among regions. Another is a pulse-tectonic cyclical terrace produced by local tectonic uplifts as dominant elements, and their distribution is restricted within an active belt and can not be compared with among regions.     

基于DEM的低阶地提取新方法

以相对易于提取的低阶地为研究对象, 提出了一种基于DEM的简便实用的低阶地提取方法。 以构建泰森多边形的方法生成拔河高度数据, 同时结合低阶地发育特征及低阶地分布区拔河高度频度统计, 提出低阶地拔河高度统计图中低阶地识别的客观标志, 从而形成了一套较为系统、 科学的基于DEM的低阶地提取分级方法, 为阶地的定量研究开拓了新思路。 在桑干河王家湾宽谷段进行实验, 结果表明低阶地提取结果与实际吻合较好, 该方法可以应用于阶地野外实测前的室内解译, 使野外调查工作更具有针对性。     

Cosmogenic nuclide burial dating at Penhill Farm: An Earlier Stone Age Acheulean locality in the lower Sundays River Valley,South Africa

Penhill Farm is an Earlier Stone Age (ESA) Acheulean archaeological site located within the southeastern Cape coastal region of South Africa. Although ESA artifacts have been known for this region since the 1950s, limited archaeological work and an inability to date the terrace context sites have prevented understanding the technological progression from the ESA to Middle Stone Age (MSA) and their placement within the Stone Age chronology of South Africa. Here we use cosmogenic ²⁶Al and ¹⁰Be to reveal a two-stage depositional history for a stone tool assemblage recovered from a debris flow deposit, with artifacts dating to ca. 1.1 Ma (million years) incorporated into a debris flow dating to ca. 0.6 Ma, thereby constraining the Penhill Farm Acheulean occupation to the Early Pleistocene.     

Luminescence dating of the Huliu River terraces in the Nihewan Basin,North China

As one of the most important regions for early human occupation in East Asia, Nihewan Basin in North China is well-known for an abundance of archaeological sites with ages spanning the last 2 Ma. In recent 10 years, more than 27 new archaeological localities have been discovered from the Yuxian (sub-basin of Nihewan), and all of them are with no age control. The lack of reliable ages for these localities affects our understanding for the evolution of the stone-tool technology in the Nihewan Basin. As many localities were founded in the river terrace, the fluvial terrace sequence of the Huliu River (main river of the Yuxian) was investigated. Based on single-grain post-infrared infrared stimulated luminescence (pIRIR) procedure on potassium (K-) feldspar, our results reveal that the formation ages of three Huliu River terraces are 139.6–115.7, 19.7–5.5, and <0.9 ka, respectively. On the basis of these pIRIR ages, the formation of the fluvial terrace sequence may provide informative constraints on the human occupation in the Huliu River terrace in the Nihewan Basin, if a clear stratigraphic correlation is established between the archaeological sites and the dated terrace deposits.     

New chronological constraints on the Plio-Pleistocene uplift of the Guizhou Plateau,SE margin of the Tibetan Plateau

The Guizhou Plateau represents a geomorphic transition between the Tibetan Plateau and the Yangtze River Plain. It likely formed in response to the propagation of surface uplift in southeastern Tibet during India-Eurasia continental collision. However, the uplift history of the region is unclear largely due to a lack of datable material. The bedrock geology is dominated by carbonate rocks, which contains numerous multi-level caves in the main river valleys that are linked to the river incision history. Cosmogenic ²⁶Al and ¹⁰Be burial dating of sediments in caves and river terraces from the northwestern and southern plateau reveals the fluvial chronology and provides the first direct determination of long-term river incision rates. The caves and terraces on the Liuchong River in NW Guizhou yield burial ages of between 0.41 ± 0.12 Ma and 2.85 ± 0.21 Ma, indicating an average incision rate of 57 ± 3 m/Ma. Four level caves at Libo in southern Guizhou yield burial ages of between 0.56 ± 0.16 Ma and 3.54 (+0.25/-0.22) Ma, indicating slightly slower incision rate (47 ± 5 m/Ma). These new results imply that the high elevation of the Guizhou Plateau had developed before the Late Pliocene, and that surface uplift during the Late Cenozoic was largely uniform across the region.     

Luminescence chronology of fossiliferous fluvial sediments along the middle Atbara River,Sudan

Fluvial sediments of the middle Atbara River Valley, eastern Sudan, contain abundant vertebrate fossils and stone tools. Previous work described two sedimentary units, the Butana Bridge Synthem (BBS) and the Khashm El Girba Synthem (KGS), with three divisions each (BBS1-3 and KGS1-3, from bottom to top, respectively). ²³⁰Th/U dating on bivalve shells suggested an age of ∼126 and ∼92 ka for the basal KGS2 and basal KGS3, respectively, and mammalian biochronology in combination with magnetostratigraphy suggested an age of late Early to early Middle Pleistocene for the underlying BBS. To establish a detailed chronology of this fluvial sedimentary sequence, we collected 17 luminescence samples from both sides of the Atbara River close to the Butana Bridge. Quartz OSL dating was applied to samples from the upper part of the profile (upper KGS2 and KGS3), but the signal reached saturation within the upper ∼10 m of the sequence. To select a suitable feldspar signal to date older samples beyond the limit of the quartz OSL, a comparison of the quartz OSL, feldspar post-IR IRSL at 225 and 290 °C, and pulsed IRSL signal at 50 °C was conducted for a sample from KGS3. The result showed that only the fading corrected pulsed IRSL yielded an age consistent with the quartz OSL, and the post-IR IRSL signals (both at 225 and 290 °C) overestimated the quartz age significantly. We therefore selected the pulsed IRSL signal to date the older deposits. The luminescence ages indicate that the entire BBS - KGS sequence was deposited between 224 ± 23 ka and <17 ± 1 ka, corresponding to marine isotope stages (MIS) 7–2, significantly revising previous conclusions.     

Petrography of alluvial sands as a past and present environmental indicator: Case of the Loire River (France)

Four sample sets of the Upper and Middle Loire river sands were analyzed in order to study the impact of natural and anthropogenic factors on their petrographic composition in space (on an 800 km stretch) and time. Composition was determined by modal analysis of three sand-size fractions using a polarizing optical microscope and calculated for each sample (“standard sand” = Sst). The watershed is composed mainly of endogenic (Massif Central) and sedimentary (southern Parisian Basin) rocks. B-set sands collected in channels for different water flows in 1996 show that Sst compositions vary by only 5 %. Present-day sands in the Upper Loire and Middle Loire have very high petrographic immaturity comparing to others worldwide fluvial sands, although bio-climatic conditions favor sand maturation by source-rock weathering in the watershed. This shows the strong impact of the Massif Central on sediment yield due to relief rejuvenation as a consequence of the formation of the Alps during the Quaternary. Fluvial sands stored during the Weichselian and the Holocene in the Middle Loire floodplain, although partly weathered since their deposition, show higher inputs from the endogenic rocks of the Massif Central than present-day deposits. This can be explained by Weichselian periglacial conditions and the development of crop farming since the Neolithic, which favored mechanical erosion, particularly in the Massif Central which is characterized by a cold, humid climate and steep slopes. The upstream-downstream change in the composition of presently deposited sand is low in the diked area. It shows however that basalt and some heavy mineral grains are vulnerable to abrasion during transport and indicates a marked sediment yield from ancient sediment stored in the floodplain. This is in line with the high incision of the river bed over the last 150 years partly due to dam construction and aggregate mining.