Complexes dunaires et tourbeux holocènes du littoral du Nord de la France     

Murielle Meurisse  Brigitte Van Vliet-Lanoë  Brigitte Talon  Philippe Recourt 《Comptes Rendus Geoscience》2005,337(7):675-684

This survey of the coastal dunes of northern France is based on stratigraphy, ¹⁴C dating, sedimentology and morphology applied for palaeoclimatic and palaeodynamic purpose. The dunes rest on a Flandrian prism sealed by Atlantic peats grown backward from a subboreal dune ridge. Two historical building phases are recorded: the late Roman dunes and the 13th century dunes. These events are separated by pedogenesis. Contribution of reworked fluvial sands also records the recent climatic degradation, with an increased storminess (Little Ice Age) associated with more efficient erosion (soil erosion and floods). The dunes of Picardy also record the Global Warming: their morphologies attest a shift from parabolic into longitudinal, by coupling storminess and sea-level rise. To cite this article: M. Meurisse et al., C. R. Geoscience 337 (2005).  相似文献   

应用于城市活断层调查的地震方法技术   总被引：22，自引：3，他引：22  

徐明才  高景华  刘建勋  荣立新 《中国地震》2005,21(1):17-23

用地震方法探测城市直下型活动断裂是一种不可替代的勘探技术。地震方法能够准确确定断层的位置，但对于断层的地质年代问题，地震方法本身难以解决，然而结合钻孔资料和测区标准地质剖面，根据地震深度剖面，可以定性地(或半定量地)确定反射波组的地质年代。确定城市直下型活动断裂的上断点需要采用高分辨率的地震反射技术，为有效地确定深部断裂的几何特征，特别是确定深浅断裂构造之间的关系，反射地震方法优于折射地震方法。  相似文献   

支气管扩张的影像诊断     

孙忠华  于红 《CT理论与应用研究》1997,6(2):44-47

支气管扩张（以下简称支扩）一直是肺部疾病的重要和常见病因。高分辨率ＣＴ使支气管成像发生变革，目前是继胸片和支气管造影之后诊断支扩的首选方法，它能更好地显示疾病临床特征和气管结构异常方面的相互关系。年来螺旋ＣＴ以其独特的成像特征成为支扩诊断的又一可靠方法。  相似文献   

Debris flows in the Swiss National Park: the influence of different flow models and varying DEM grid size on modeling results   总被引：1，自引：0，他引：1  

Adrian Stolz  Christian Huggel 《Landslides》2008,5(3):311-319

In the Swiss National Park, debris flows are a frequent phenomenon and have repeatedly affected highways and hiking structures. In this study, we first investigated the main characteristics and dimensions of current debris flows by field work and empirical parameterization schemes. Additionally, we evaluated a topography-based flow-trajectory geographic information system model (MSF) and a flow-routing model (FLO-2D) in terms of debris flow-affected areas. Three generically different digital elevation models (DEM) with grid spacing of 25, 4, and 1 m were used in conjunction with the flow models. The evaluation of the DEM grid spacing shows that for both flow models the 25-m DEM can give an approximate estimation of the potential hazard zone. Four- and one-meter DEMs mostly confine the simulated debris flow to existing channels and are in accordance with observations of recent debris-flow events. The study shows that DEM quality and grid resolution are crucial for the resulting delineation of potentially affected areas and thus for hazard assessment and mapping.  相似文献   

Temporal and Spatial Sampling Constraints in High-Resolution 3-D Seismic Surveys     

Abdulah  K. C.  Anderson  J. B.  Coperude  S.  Canning  A. 《Marine Geophysical Researches》1997,19(2):97-113

An experimental, high-resolution 3-D seismic survey was acquired over a 1.5 km2 section of an incised fluvial valley. The data were acquired as a near-zero offset, single-channel survey using a 15 in3 water gun as the source, and differential GPS for navigation and positioning. The objective was to acquire a 3-D seismic data volume suitable for calculating the volume of shallow sand deposits. Horizontal time sections from the 3-D volume clearly show the flanks of the incised valley, as well as high-amplitude reflections interpreted as coarse-grained channel-lag deposits. The volume of this lag deposit can be calculated using the combination of the horizontal and vertical sections from the high-resolution 3-D seismic data set. The results of the experiment also illustrate the importance of spatial sampling in 3-D seismic surveying.  相似文献   

ECMWF高分辨率数值模式对广安地区暴雨预报性能检验分析          下载免费PDF全文

王平 《中低纬山地气象》2018,42(6):44-49

为了解ECMWF高分辨率数值预报模式(以下简称"ECMWF")对广安地区暴雨的预报性能,提高预报质量。利用ECMWF模式资料、广安地区4个国家观测站和160个区域自动站的逐日降水资料,对2015—2017年广安地区出现的34次中雨及以上量级降水(其中14次暴雨)天气过程进行分析。结果表明:直接以ECMWF暴雨预报结果进行暴雨预报,易出现漏报,评分质量较低。当ECMWF预报满足:中、短期均预报降水R≥50 mm;中期预报R≥25 mm、短期预报R≥50 mm;中期预报R≥50 mm、短期预报R≥25 mm;中、短期均预报R≥35 mm 4个订正条件之一时,进行订正预报暴雨,评分高,空、漏报率低,命中率高,可有效提高暴雨预报质量。同时,ECMWF在暴雨的持续时间、强降水时段、落区和面雨量预报中均有良好的预报指导意义。  相似文献   

Analysis and high-resolution modeling of a dense sea fog event over the Yellow Sea   总被引：12，自引：0，他引：12  

Gang Fu  Jingtian Guo  Shang-Ping Xie  Yihong Duan  Meigen Zhang 《Atmospheric Research》2006,81(4):293-303

A ubiquitous feature of the Yellow Sea (YS) is the frequent occurrence of the sea fog in spring and summer season. An extremely dense sea fog event was observed around the Shandong Peninsula in the morning of 11 April 2004. This fog patch, with a spatial scale of several hundreds kilometers and lasted about 20 h, reduced the horizontal visibility to be less than 20 m in some locations, and caused a series of traffic collisions and 12 injuries on the coastal stretch of a major highway. In this paper, almost all available observational data, including Geostationary Operational Environmental Satellite (GOES)-9 visible satellite imagery, objectively reanalyzed data of final run analysis (FNL) issued by the National Center for Environmental Prediction (NCEP) and the sounding data of Qingdao and Dalian, as well as the latest 4.4 version of Regional Atmospheric Modeling System (RAMS) model, were employed to investigate this sea fog case. Its evolutionary process and the environmental conditions that led to the fog formation were examined by using GOES-9 visible satellite imagery and sounding observations. In order to better understand the fog formation mechanism, a high-resolution RAMS modeling of 4 km × 4 km was designed. The modeling was initialized and validated by FNL data. A 30-h modeling that started from 18 UTC 10 April 2004 reproduced the main characteristics of this fog event. The simulated lower horizontal visibility area agreed reasonably well with the sea fog region identified from the satellite imagery. Advection cooling effect seemed to play a significant role for the fog formation.  相似文献   

Exploration and Research of Deep Crustal Structures in the Zhangzhou Basin and Its Vicinity   总被引：1，自引：0，他引：1  

Zhu Jinfang 《中国地震研究》2006,20(4):412-425

INTRODUCTIONThe Zhangzhou basinislocated onthe southeast coast of Fujian Province .Interms of geotectonicunits ,it lies in the east Fujian volcanic fault-depression zone between the Wuyi-Daiyun mountainupheaval zone and depression zone of Taiwan Straits of the south China block. In terms ofseismotectonics ,it islocatedinthe middle sectionof the southeasterncoastal seismic zone .In history,the area was influenced by repeated destructive earthquakes , and the seismic activity was closely…  相似文献   

Shallow high-resolution seismics and reprocessing of industry profiles in southern Bavaria: The Molasse and the northern Alpine front   总被引：1，自引：0，他引：1  

Rüdiger Thomas  Klaus Schwerd  Kurt Bram  Jürgen Fertig 《Tectonophysics》2006,414(1-4):87

The purpose of this seismic investigation in the Upper Bavarian Miesbach area, as part of the international TRANSALP project, was to study the tectonic contact between the autochthonous Foreland Molasse and the allochthonous Folded Molasse marking the tectonic front of the Alpine orogen. Another specific target was the dip of the frontal emerging main thrust of the tectonic units Helveticum/Ultrahelveticum and Rhenodanubian Flysch overriding the Folded Molasse. Twelve seismic profiles obtained from the hydrocarbon industry were reprocessed. From the Foreland Molasse southward to the Autochthonous Molasse in the subsurface of the overthrust Folded Molasse conspicuous features such as steep normal faults at the Molasse base, S-directed thickening of Molasse sediments or sedimentary discordant base of Upper Marine Molasse can be recognized.Shallow high-resolution seismic measurements were conducted along two profiles across the tectonic contact between Foreland Molasse and Folded Molasse, as well as along a profile across the frontal emerging main thrust of the Helveticum/Ultrahelveticum and the Rhenodanubian Flysch. Geological structures could be identified in the top 300–500 ms two-way traveltime interval, which is hardly possible with the usual deep-seismic method. The method thus provides a bridge between deep-reflection seismics and surface geology.In contrast to the western Bavarian Molasse zone, the tectonic boundary between the Foreland Molasse and the Folded Molasse in the investigated area is not characterized by a large blind-thrust triangle zone but by a simple south-dipping thrust plane. Adjacent to the S follow several steeply south-dipping inverse Molasse thrust slices and the Miesbach syncline. The inverse thrust slices are interpreted as the overturned and sheared northern limb of a fault propagation fold, which linked the Folded Molasse to the Foreland Molasse during a final orogenic phase.The main thrust of the Helveticum/Ultrahelveticum and the Rhenodanubian Flysch are well imaged in the near-surface interval of the high-resolution reflection seismic data. In contrast to previously published results, these thrust planes show a gentle dip to the S from the surface down to at least 500–1000 m depth.  相似文献   

海南岛近2500a来盘星藻记录的周期性气候变化   总被引：9，自引：2，他引：9  

张华  郑卓  王建华  王斌  邓韫  邹和平 《热带地理》2004,24(2):109-112,122,F003

湖泊沉积物中盘星藻含量变化可以反映湖泊水环境特征，对海南岛双池玛珥湖沉积物中盘星藻的研究发现，热带湖泊盘星藻种类以浮游类单角盘星藻为主，其含量在最近2500a以来相当丰富，而且其数量浓度的变化与湖水深度关系密切。频谱分析结果表明，近两千多年来盘星藻含量存在一个主要周期和一个次要周期，分别为421a和218a，前者与湛江湖光岩的结果可以对比，而后者则与206a的宇宙核素周期(^14C和^10Pe)十分接近。  相似文献