Onshore and offshore seismic and lithostratigraphic analysis of a deeply incised Quaternary buried valley system in the Northern Netherlands     

Sjoerd J. Kluiving  J. H. Aleid Bosch  Jan H. J. Ebbing  Chris S. Mesdag  Rogier S. Westerhoff 《Journal of Applied Geophysics》2003,53(4):249

High-resolution seismic data (onshore and offshore), geophysical borehole data as well as detailed lithofacies from airlift boreholes were acquired in northern Netherlands on and around the island of Ameland. Marine and land seismic data combined with information from land boreholes have been explored with the objective of providing a sedimentary model. Qualitative seismic facies analysis of the valley fill commonly shows a thin unit with high amplitude reflectors at the base. Thick units of variable seismic facies (transparent to high amplitude) occur higher up in the sequence. Onlap is common at mid–upper levels within the sandy valley fill (with clay in mm layering), and a transparent seismic facies, corresponding to firm clays, is common at the top. Almost all lithological unit boundaries recognised within core parameters correspond with seismic unconformities within error margins. Subunits contain multiple cyclical trends in gamma ray and grain size. Cyclical trends show lower order fluctuations in gamma radiation on a scale of less than 1 m. Gamma-ray pattern variability between units, e.g. in general coarsening-up or fining-up units, suggests migration of subaqueous outwash fans or ice margin fluctuations. Seismic results could support a headward excavation and backfilling process suggested by Praeg [Morphology, stratigraphy and genesis of buried Elsterian tunnel valleys in the southern North Sea basin [PhD thesis]: University of Edinburgh, 207 pp.; Journal of Applied Geophysics, (this volume)] as being responsible for the formation of buried valleys. On a lithological scale, a more complicated, detailed and cyclical pattern arises. Catastrophic processes are considered unlikely as being responsible for the infill sequence because of the observed small-scale facies variability and because of the presence of diamicton layers. Diamicton layers at the base of basal unconformities as well as higher in sequence could suggest subglacial deformation by grounded ice before and during the valley-fill process.  相似文献   

A hybrid indirect boundary element—discrete wave number method applied to simulate the seismic response of stratified alluvial valleys     

S. A. Gil-Zepeda  J. C. Montalvo-Arrieta  R. Vai  F. J. Snchez-Sesma 《Soil Dynamics and Earthquake Engineering》2003,23(1):77-86

A hybrid indirect boundary element – discrete wavenumber method is presented and applied to model the ground motion on stratified alluvial valleys under incident plane SH waves from an elastic half-space. The method is based on the single-layer integral representation for diffracted waves. Refracted waves in the horizontally stratified region can be expressed as a linear superposition of solutions for a set of discrete wavenumbers. These solutions are obtained in terms of the Thomson–Haskell propagators formalism. Boundary conditions of continuity of displacements and tractions along the common boundary between the half-space and the stratified region lead to a system of equations for the sources strengths and the coefficients of the plane wave expansion. Although the regions share the boundary, the discretization schemes are different for both sides: for the exterior region, it is based on the numerical and analytical integration of exact Green's functions for displacements and tractions whereas for the layered part, a collocation approach is used. In order to validate this approach results are compared for well-known cases studied in the literature. A homogeneous trapezoidal valley and a parabolic stratified valley were studied and excellent agreement with previous computations was found. An example is given for a stratified inclusion model of an alluvial deposit with an irregular interface with the half-space. Results are displayed in both frequency and time domains. These results show the significant influence of lateral heterogeneity and the emergence of locally generated surface waves in the seismic response of alluvial valleys.  相似文献   

La vallée d'Ys : un paléoréseau hydrographique immergé en baie de Douarnenez (Finistère,France)     

Gwénaël Jouet  Claude Augris  Bernard Hallegouët  Pascal Le Roy  Joël Rolet 《Comptes Rendus Geoscience》2003,335(5):487-494

Interpretation of the recent high-resolution survey, CANADOU 2000, in the Bay of Douarnenez (Finistère, France) allowed us to restore the morphology of the substratum and the sedimentary filling of the bay. The Brioverian and Palaeozoic substratum reveals a well-defined network of incised valleys as results of successive emergence stages of the Bay during the Quaternary. Valleys join in a westward-widened mean valley, called Ys Valley. The present-day sedimentary fill of the bay of Douarnenez appears mainly controlled by the Holocene rise and the consecutive highstand. It comprises fluvial and estuarine deposits filling up incised valleys and marine sedimentation extending out of the incised valleys. To cite this article: G. Jouet et al., C. R. Geoscience 335 (2003).To cite this article: G. Jouet et al., C. R. Geoscience 335 (2003).  相似文献   

河南省短期区域性暴雨动力诊断及综合预报方案          下载免费PDF全文

李平  孙景兰  张金彬  孔海江  李保生  闫少伟 《气象》1997,23(8):25-28

介介绍了（１）用Ｔ６３数值预报产品对河南省省６－８月区域性暴雨进行物理量诊断分析。（２）用人工智能研制的河南省６－８月分片大－暴雨短短期自动化预报系统与用Ｔ６３数值预报产品资料采用逐步回归分析法和预测误差平方和最不上准则两种选取回归自变量的方法，建立处分片预报方程的综合判别预报。（３）在１９９５，１９９６年７－８月业务预报中试验结果。  相似文献   

中国北部边疆第四系地下水研究     

李国安  韩朝平 《第四纪研究》1996,16(2):105-114

在中国北部边疆西起天山东端的北山，东至大兴安岭北段的４２００ｋｍ地域内，气候干旱少雨，水资源贫乏，第四系地下水是主要供水源之一。本文首次比较系统地研究了该区第四纪堆积物的分布和地下水的赋存规律。文中依据不同地貌单元、地层岩性及气候条件诸因素将本区第四系地下水划分为枝状沟谷砂砾石层孔隙水、河谷冲积平原砂砾石层孔隙水两种主要类型，并着重对有重要供水意义的河谷冲积平原砂砾石层孔隙水的分布、埋藏条件、富水性及水化学特征进行了论述。  相似文献   

山谷冰川稳定态时积累区面积比率研究     

王宁练  薄健辰 《冰川冻土》1997,19(2):167-172

探讨山谷冰川稳定状态时积累区面积比率，即ＡＡＲ值的大小，认为冰川物质平衡高程分布，平面形态及坡面坡度沿程变化形式是影响山谷冰川稳定态ＡＡＲ值的主要因素，并 山谷冰川稳定态ＡＡＲ值与物质平衡高程分布及平面形态之间的定量关系。山谷冰川适合于应用ＡＲ值法来研究古冰川的零平衡线高程。  相似文献   

大连市滨海河谷地下水资源开发利用的可行性     

王卫东  宋庆春  李宝兰  巩建伟 《华北地质》2004,27(4):268-272

大连市是我国严重缺水地区之一 ,至 2 0 0 5年城市缺水为 110 4 2 .5× 10 4m3 ,占需水量的 17.1% ,其中大连城区 (金州以南地区 )缺水 9890× 10 4m3 ,占缺水量的 89.6 %。开发利用滨海河谷地下水资源 ,建立滨海河谷型地下水库 ,不仅可以治理大连地区严重的海水入侵问题 ,增加水资源量 ,满足当地农业及生活用水 ,同时可弥补城市供水的不足。根据前人工作成果分析及野外实地勘查 ,大连市适于建设河谷型地下水库的滨海河谷有 2 2条 ,建成后的总库容量 10 36 0 2 .9× 10 4m3 ,开采资源量 2 5 76 6 .88× 10 4m3 ,可增加开采资源量 12 5 4 2 .4 5× 10 4m3 。  相似文献   

晚更新世晚期以来的长江上游古洪水记录   总被引：4，自引：2，他引：4       下载免费PDF全文

葛兆帅  杨达源  李徐生  任朝霞 《第四纪研究》2004,24(4):555-560

长江上游三峡河段主要的古洪水记录有:1)三峡深槽的蚀积变化;2)长江阶地粗粒沉积;3)长江的泛滥沉积;4)长江的古洪水平流沉积。不同时间跨度不同类型古洪水记录的精度有较大的差别。古洪水记录显示,晚更新世晚期的40～30kaB.P.,长江上游大洪水比30kaB.P.以来的长江上游大洪水大得多;全新世以来,以3983aB.P.前后的大洪水为相对最大;公元1870年大洪水为3000aB.P.以来最大洪水;近百年来的实测洪水以公元1981年洪水为最大。  相似文献   

Character of Terrestrial Sequence Stratigraphy and Depositional System in Incised Valley, Outcrop Area of Karamay Oilfield, Junggar Basin, China   总被引：1，自引：0，他引：1  

JiaoYangquan YanJiaxin LiSitian YangRuiqi LangFengjiang YangShengke 《中国地质大学学报(英文版)》2004,15(3):324-334

  相似文献   

元谋干热河谷坡耕地土壤侵蚀造成的土地退化   总被引：13，自引：0，他引：13  

陈奇伯  王克勤  李金洪  朱国进  李跃 《山地学报》2004,22(5):528-532

在元谋干热河谷土壤侵蚀特征分析的基础上，对坡耕地土壤侵蚀造成的土地退化进行了模拟研究。结果表明，土壤侵蚀造成表层耕作土壤的物理性能下降、养分流失和水分入渗能力降低。表层耕作土壤的容重比下层土壤低12．7％，总孔隙度高10．9％，有机质高37．3％，120min累计入渗总量是下层土壤的1．6-2．2倍。模拟土壤侵蚀与土地生产力关系的小区试验结果显示，坡耕地每流失1cm表土，土地生产力水平平均下降4．54％。  相似文献