Episodic fluid flow as a trigger for Miocene‐Pliocene slope instability on the Utgard High,Norwegian Sea     

《Basin Research》2018,30(5):942-964

Mass wasting is triggered on many continental slopes by a number of mechanisms, including seismic shaking, high sedimentation rates, the presence of weak geological units and gas hydrate dissociation. In this study, the morphology of a Late Miocene–Early Pliocene mass‐transport complex (MTC) on the Utgard High is unravelled and discussed in relation to possible trigger mechanisms. The approach used here includes 3D seismic interpretation and the analysis of variance attribute maps. The interpreted MTC is located on the crest and flanks of the Utgard High and is composed of three mass‐transport deposits with seismic characters varying from transparent and chaotic seismic facies at the base to slightly deformed layers composed of mounds and rafted blocks in the middle and chaotic to transparent reflections at the top. Lithologically, the MTC consists predominantly of claystone with high gamma ray and low density and resistivity values, demonstrating that the associated mounds represent remobilized ooze sediments. A vertical stack of six magmatic sills emplaced from 55.6 to 56.3 Ma into the Upper Cretaceous shales is interpreted at depths of 3,000–5,500 ms two‐way travel time (TWTT). In association with these magmatic sills are several hydrothermal vent complexes that interacted with the top MTC horizon, signifying that episodic and secondary fluid‐venting events might be the principal mechanism facilitating mass wasting in the study area. In addition, the remobilization of ooze sediments into mounds is hypothesized to be dependent on fluids and clayey layers. As a corollary of this work, the importance of relict and recurrent episodes of fluid flow in the Vøring Basin and their influence on the geotechnical integrity of the overburden and later mass wasting is established.  相似文献   

基于葵花8卫星的上海市夏季对流初生预报研究   总被引：2，自引：0，他引：2  

郭巍  崔林丽  顾问  王超  麻炳欣 《气象》2018,44(9):1229-1236

参考Mecikalski et al(2010a;2010b)提出的基于GOES系列卫星的对流初生预报方法,针对上海市夏季对流天气特征建立了基于高时空分辨率的静止气象卫星数据的上海市对流初生判识及预报方法。利用该方法对上海市的一次对流初生个例进行了分析,并对2016年7-8月的12次对流初生事件进行了预报试验,结果表明:方法提取的各个指标能够很好地体现对流初生过程中云团的发展变化特征并能剔除掉成熟对流云团边缘像元的干扰;在12次对流初生事件中,成功地预报了其中的11次,预报时间较对流初生时间平均提前了约30 min,但是对于局地弱对流过程该方法仍有一定的缺陷。  相似文献   

基于潮汐动态淹没过程的长江口潮滩地形信息反演研究     

章敏  吴文挺  汪小钦  孙玉 《地球信息科学学报》2022,24(3):583-596

潮滩是陆地与海洋之间重要的生态过渡地带,具有复杂的生态过程和重要的服务功能。受陆海交互作用及人类活动的影响,潮滩处于高度动态变化过程中,而传统测绘技术受到潮滩可达性影响无法快速获取潮滩地形信息。为解决潮滩高程数据获取困难的问题,本文提出一种基于潮汐动态淹没过程和时序遥感影像的潮滩地形信息提取算法,利用K-means++聚类方法实现水域提取,并通过时序淹没特征计算潮滩淹没频率提取潮滩范围信息,最终综合区域潮汐特征反演潮滩地形。研究以崇明东滩为例,利用2016—2020年所有可用Sentinel-2和Landsat-8时序遥感影像,实现潮滩范围提取与高程反演,并通过实测高程数据进行精度验证。研究结果表明,潮滩范围提取总体精度为97.73%,F1_score为0.98;高程反演平均绝对误差为0.15 m,潮滩高程的反演精度与可用影像的数量呈正相关。研究利用该算法进一步反演长江口地区主要潮滩地形特征,结果表明区域内潮滩面积为346.93 km²,高程范围为1.00~3.84 m,且与现有潮滩范围数据集相比,本研究提取的长江口潮滩范围更为完整。该算法为潮滩地形的快速反演提供了可能,对潮滩资源动态监测和管理具有重要意义。  相似文献   

A Comparative Study of Landsat‐7 and Landsat‐8 Data Using Image Processing Methods for Hydrothermal Alteration Mapping          下载免费PDF全文

Feizollah Masoumi  Taymour Eslamkish  Mehdi Honarmand  Ali Akbar Abkar 《Resource Geology》2017,67(1):72-88

Comparing spaceborne satellite images of Landsat‐8 Operational Land Imager (OLI) and Landsat‐7 Enhanced Thematic Mapper plus (ETM+) was undertaken to investigate the relative accuracy of mapping hydrothermal alteration minerals. The study investigated the northern part of Rabor, which contains copper mineralization occurrences, and is located in the Kerman Cenozoic magmatic assemblage (KCMA), Iran. Image processing methods of band ratio, principal component analysis (PCA), and spectral angle mapper (SAM) were used to map the distribution of hydrothermally altered rocks associated with the porphyry copper mineralization. The band ratio combination of both sensors for mapping altered areas showed similar outcomes. PCA exposed variations in the spatial distribution of hydroxyl‐bearing minerals. The representation of hydrothermal areas using OLI data was more satisfactory than when using ETM+ data. SAM analysis found similar results for mapping hydroxyl‐bearing zones. Verification of the results came through ground investigation and laboratory studies. Rock samples (n = 56) were collected to validate results using thin sections, X‐ray diffraction (XRD) and spectral analyses. Field observations and laboratory analysis revealed that phyllic and propylitic alterations dominate the alteration zones in the study area. Argillic and iron oxides/hydroxides alterations were observed to a lesser degree. The results indicate that alteration maps prepared by OLI data using PCA for visual interpretation are more suitable than those of ETM+ due to a higher radiometric resolution and lower interference between vegetation and altered areas. As the spectral bandwidth of ETM+ band 7 covers absorption feature of propylitic alteration, better mapping of propylitic alterations is achieved using ETM+ data.  相似文献   

鄂尔多斯盆地姬塬西部三叠系延长组长8油层组成岩作用与致密化过程^*          下载免费PDF全文

汪洋  刘洛夫  李树同  吉海涛  李林泽  罗泽华  许同 《古地理学报》2017,19(5):892-906

利用岩心、铸体薄片、扫描电镜、碳氧同位素及流体包裹体等资料,对鄂尔多斯盆地姬塬西部三叠系延长组长8油层组致密储集层特征进行了研究,重点分析了储集层成岩作用特征和储集层致密化成因机制及过程。研究区长8油层组砂岩主要为岩屑长石砂岩和长石岩屑砂岩,经历了压实—压溶、胶结、交代、溶蚀及构造破裂等成岩作用,整体处于中成岩A期晚期。典型成岩序列依次为机械压实、绿泥石黏土膜、早期(泥晶)方解石胶结、石英次生加大、长石、岩屑溶蚀、自生高岭石胶结、自生石英胶结、中期(含)铁方解石胶结。综合研究认为:(1)近物源伴随湖平面快速上升的沉积环境提供了储集层致密化的物质基础,不同沉积微相储集层物性差别较大,分流河道最好,分流间湾最差;(2)长8油层组原始孔隙度为41.35%,压实作用损孔率为50.67%,造成储集层孔隙度急剧降低,胶结作用损孔率为37.48%,导致孔隙度进一步减小,溶蚀作用仅增加了3.26%的孔隙度,难以有效改善储集层质量;(3)上述沉积与成岩因素共同导致储集层致密,致密化过程可分为压实孔隙骤减阶段、早期胶结减孔阶段、溶蚀作用增孔阶段和晚期胶结致密阶段共4个阶段;(4)油气大量充注期储集层孔隙度远低于10%,长8油层组先致密后成藏。  相似文献   

唐山7.8级地震前的震中迁移与远台前兆的关系     

郭增建  郭安宁 《华北地震科学》2014,(4):1-3

以震中迁移始发点的前兆讨论了唐山7.8级地震震中位置的预测,并以此为例分析了汶川8级地震和芦山7级地震的前兆问题。另外,从震中迁移延长线上的前兆来讨论了唐山大震的发生时间。  相似文献   

冻土工程与环境研究的新进展——第八届国际冻土工程会议回顾     

牛富俊  李国玉  赵淑萍  张淑娟  赵永国 《冰川冻土》2009,31(6):1166-1177

2009年10月在西安召开第八届国际冻土工程会议, 就冻土地区工程设计与建设、季节冻土区工程冻害防治、冻土物理力学特性、 模型发展及其应用、寒区气候、环境及冷生变化、多年冻土水文学、寒区水资源和土地应用等主要议题进行了广泛交流, 报告了近年来冻土工程与环境研究方面的一些新进展. 从冻土工程设计、施工和评价、普通冻土研究、冻土的物理力学性质、冻土模型发展及应用、 气候变化及冰冻圈环境等方面对该次会议交流的成果进行了总结. 与会研究者认为今后的研究一方面要加强理论研究、工程措施机理研究;另一方面要加强寒区环境对气候变化的响应及反馈、以及环境变化与冻土工程措施之间的相互作用研究.  相似文献   

姬塬地区长8油层组浅水三角洲沉积特征   总被引：22，自引：4，他引：18  

韩永林  王成玉  王海红  李士春  郑荣才  王昌勇  廖一 《沉积学报》2009,27(6):1057-1067

姬塬地区位于鄂尔多斯盆地中偏西部地区,晚三叠世主要受北东、北西及南部三个方向的物源控制。通过岩心观察、薄片鉴定、测井曲线等资料的综合分析,对研究区上三叠统长8油层组岩石类型、沉积构造、物源方向、古生物和沉积相特征进行了详细研究,发现长8沉积时期姬塬地区地形平缓,河流作用较弱,主要发育一套浅水三角洲沉积体系,其沉积作用和砂体展布受湖平面升、降和物源方向控制明显,对油气成藏有着重要的意义,表现为:①湖平面上升期,湖岸线快速向物源方向迁移,以发育长条状和鸟足状水上—水下分流河道砂体为主;②下降期以发育三角洲平原为主,来自不同物源方向的前缘砂体在研究区中部交汇;③湖平面上升期水下分流河道砂体呈席状发育以及岩性遮挡条件更好,因而比湖平面下降期发育的砂体更有利于形成岩性油藏。  相似文献   

Rest‐frame UV to optical X‐shooter spectrum of the gravitationally lensed galaxy “the 8 o'clock arc”: Dissection of its physical properties     

M. Dessauges‐Zavadsky  S. D'Odorico  L. Christensen  D. Schaerer  J. Richard 《Astronomische Nachrichten》2011,332(3):307-308

We present the rest‐frame UV to optical spectrum of the gravitationally lensed galaxy, the “8 o'clock arc” at z = 2.735, obtained with the X‐shooter spectrograph. This is one of the rare comprehensive study of a high‐redshift star‐forming galaxy, usually not feasible due to the faintness of these objects. The spectrum of the 8 o'clock arc is rich in stellar and interstellar absorption features and in nebular emission features. Their analysis allowed us to derive most of the physical properties characterizing the galaxy. From HST images, we reconstruct the morphology of the arc in the source plane and confirm that we resolve a clump in rotation around the main core of galaxy in our X‐shooter spectrum (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Enrichment of seismic ground motion databases using Karhunen–Loève expansion     

Irmela Zentner  Fabrice Poirion 《地震工程与结构动力学》2012,41(14):1945-1957

Best estimate seismic analysis are generally based on time‐domain simulations of structural responses. The seismic load is then modeled by a stochastic process representing ground motion. For this purpose, the analyst can use recorded accelerograms or work with synthetically generated ones. The number of ground motion time‐histories available for a given scenario and site condition is limited and generally not sufficient for carrying out more advanced probabilistic structural response analysis. It is then necessary to have at our disposal methods that allow for generating synthetic accelerograms that realistically characterize earthquake ground motions. However, most of the methods proposed in literature for generating synthetic accelerograms do not accurately reproduce the natural variability of ground motion parameters (such as PGA, cumulative absolute velocity, and Arias intensity) observed for recorded time histories. In this paper, we introduce a new method for generating synthetic ground motion, based on Karhunen‐Loève decomposition and a non‐Gaussian stochastic model. The proposed method enables the structural analyst to simulate ground motion time histories featuring the properties mentioned above. To demonstrate its capability, we study the influence of the simulation method on different ground motion parameters and on soil response spectra. We finally compute fragility curves to illustrate the practical application of the proposed method. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献