湖南省中南部地区地震区划研究   总被引：3，自引：0，他引：3  

李颖  胥广银  陈鲲  高孟潭 《中国地震》2007,23(1):17-24

选择湖南省中南部地区作为研究区域,以编制《中国地震动参数区划图》的基础资料和近年来在湖南省中南部所作的工程场地地震安全性评价资料为基础,根据近年来对中强地震衰减关系的研究结果,以及1970年以来现代仪器记录得到的地震资料确定的研究区域背景地震活动水平及其参数,对湖南省中南部地区进行了新的地震区划研究。结果表明,考虑了中强地震衰减关系,并重新考虑背景地震活动水平后,湖南中南部地区地震区划结果与现行区划图相比,地震动峰值加速度达0·05g的区域显著增加,其中包括邵阳、湘潭、吉首、怀化等重要城市。研究结果与近年来湖南中南部地区发生的中小地震的高震害特征比较吻合。本文的研究结果对于地震活动主要以6级以下中强地震活动为主的我国中东部地区的地震区划研究以及编制新一代地震动参数区划图都具有重要的参考意义。  相似文献   

Upper Silurian–Middle Devonian radiolarian zones of the Yokokurayama and Konomori areas in the Kurosegawa Belt, Southwest Japan     

M. Umeda 《Island Arc》1998,7(4):637-646

Five radiolarian zones, from the Upper Silurian to Middle Devonian, are discriminated from the tuffaceous successions of the Joryu and Nakahata Formations of the Yokokurayama Group of the Yokokurayama area and the Konomori area in the Kurosegawa Belt, Southwest Japan. The definition of the zones is based on the first appearance biohorizon of the characteristic species. The zones are the Pseudospongoprunum sagittatum, Futobari solidus, Trilonche (?) sp. A, Glanta fragilis and Protoholoeciscus hindea zones, in ascending order. The preliminary age assignments for the zones are discussed on the basis of the comparison with other previous documented faunas. The age determination of the formations suggests the presence of unconformities and the episodic sedimentation of the tuffaceous strata in the Yokokurayama Group.  相似文献   

“三江”地区北段某多元素异常带的特征及找矿前景分析     

罗正春 《四川地质学报》1998,(4)

１∶２０万区域化探扫面圈定出“三江”地区北段某多元素异常带,呈北西南东向条带状展布。由Ｗ、Ｍｏ、Ｃｕ、Ｂｉ、Ｕ、Ｓｎ、Ａｇ、Ｃｄ、Ｐｂ、Ｚｎ、Ａｓ、Ｂａ、Ｈｇ、Ａｕ等高中低温热液成矿与伴生元素组成于一体,具典型的浓度分带与组分分带特征。它位于玉龙斑岩铜矿带北侧,对该异常带的解剖,具重要的理论与实际意义。  相似文献   

Delineation of spatial redox zones using discriminant analysis and geochemical modelling in arsenic‐affected alluvial aquifers     

Jin‐Jing Lee  Cheng‐Shin Jang  Sheng‐Wei Wang  Chin‐Ping Liang  Chen‐Wuing Liu 《水文研究》2008,22(16):3029-3041

This study characterized the redox conditions in arsenic‐affected groundwater aquifers of the Lanyang plain, Taiwan. Discriminant analysis was adopted to delineate three redox zones (oxidative, transitional and reductive zones) in different aquifers and yielded 92·3% correctness on groundwater quality data. Arsenic is mainly distributed in the reductive zone, and arsenic distribution in the shallow aquifer is mainly affected by surface activities. According to PHREEQC modelling results, possible mechanisms for arsenic release to groundwater in Lanyang plain are explored. Arsenic released to groundwater in the oxidative zone (zone 1) is primarily caused by the oxidations of arsenic‐bearing pyrite minerals, and arsenate is the predominant species. While the reductive dissolution of Fe‐oxides are responsible for the high arsenic concentration found in the transitional and reductive zones (zones 2 and 3), arsenite is the predominant species. The reduction potential of groundwater rises as the depths and zones increase. Some sulphates may be reduced to form sulphide ions, which then react with arsenic to form arseno‐sulphide deposits (such as realgar, orpiment) and then slightly lower groundwater arsenic concentrations. A conceptual diagram which summarized the possible release processes of arsenic in different redox zones along groundwater flow in Lanyang plain is postulated. Arsenic‐bearing pyrite and arsenopyrite (FeAsS) are oxidized as they are exposed to the infiltrated oxygenated rainwater, releasing soluble arsenate Fe(II) and SO₄^2? into zone 1. The dissolution of arsenic‐rich Fe‐oxides due to the onset of reducing conditions in zones 2 and 3 is responsible for the mobility of arsenic and likely to be the primary mechanism of arsenic release to groundwater in the Lanyang plain Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Temporal and spatial zonation of macroepiphytes on Posidonia oceanica (L.) Delile leaves in a meadow off Tunisia          下载免费PDF全文

Lotfi Mabrouk  Mounir Ben Brahim  Asma Hamza  Med‐Najmeddine Bradai 《Marine Ecology》2015,36(1):77-92

The aim of this survey was to study the cover and the composition of macroepiphytic species on the leaves of Posidonia oceanica in the east of Tunisia. Surveys were conducted in December 2009 (winter period), March (spring period) and August 2010 (summer period) in a fringing reef located in Chebba. At each sampling date, 15 adult leaves were randomly collected and divided into basal and apical parts. The inner face of each part was examined with ocular glasses and microscope to estimate species cover by orthogonal projection. PERMANOVA and ANOSIM were used to test for differences of cover between sampling dates and leaf parts. SIMPER, cluster analysis, and PCA were used to ordinate species assemblages. Comparison of epiphytic cover along leaf blades showed significant differences for all groups, except cyanophycea, with high cover of hydrozoans and bryozoans in the basal part and high cover of algae in the apical part. The species composition and cover also vary with sampling date; minimum values were detected in December and the epiphytic community was composed of a few pioneer species, whereas maximum epiphytic cover values were registered in August, with the epiphytic community being composed of a more mature and more diverse community, termed ‘climax’. The main regulatory factors for this distribution are discussed.  相似文献   

(U-Th)/He测年技术:α离子射出效应及其校正   总被引：1，自引：0，他引：1  

常远  许长海  周祖翼 《地球科学进展》2010,25(4):418-427

(u-Th)/He测年技术是近年来低温热年代学研究领域快速发展的一个重要分支,被应用于磷灰石、锆石、榍石、石榴子石等多种矿物,并且磷灰石(U-Th)/He在目前已知的所用低温热年代学指标中具有最低的封闭温度和较强的热敏感性,此外矿物的(U-Th)/He分析还可用来反演样品所经历的热历史,因此该技术在地质学中得到了广泛的应用.随着对(U-Th)/He方法研究程度的提高,影响测年结果的各种因素也被相继发现和认识.从(U-Th)/He测年的基本原理出发,详细介绍了矿物内 α离子的射出效应及其对氦年龄计算的影响与校正,进一步说明了矿物成分环带、晶体形状、比表面积等因素对于氦年龄校正的作用,并详细阐述了已有的针对这些因素的不同校正模型的原理、特点、发展历程以及前缘研究方向.  相似文献   

新疆东天山红石金矿床原生晕特征与矿体叠加模型     

王世新  杨毅恒 《世界地质》2010,29(3):383-391

红石金矿床是新疆东天山康古尔塔格金矿带中的代表性矿床之一。通过对其地表、已开采中段及部分钻孔的岩石系统采样分析和计算统计,研究了各指示元素在不同位置的组合特征。结果表明:指示元素中Au、Ag密切相关,其他元素组合复杂多变,反映了成矿成晕的多期性、多阶段特点。结合实际勘查资料,采用多种计算方法,建立了矿床原生晕轴向分带模式,即矿床轴向分带(自上而下)为Bi-Mo-Hg-Zn-Pb-Ag-As-Cu-Sb-Au。利用不同中段的7个分带评价值指标确定了矿体的叠加模型。  相似文献   

Submarine groundwater discharge and benthic biogeochemical zonation in the Huanghe River Estuary     

Guangquan Chen  Bochao Xu  Shibin Zhao  Disong Yang  William C.Burnett  Shaobo Diao  Maosheng Gao  Xingyong Xu  Lisha Wang 《海洋学报(英文版)》2022,41(1):11-20

Submarine groundwater discharge(SGD) has received increasing attention by studies on coastal areas; however,its effects on biogeochemical zonation have not been investigated to date. The Huanghe River Estuary(HRE) is a world class river estuary with high turbidity, and heavy human regulation. This study investigated how SGD is related to the benthic biogeochemistry of the HRE. Based on the distribution of several parameters(e.g., salinity,temperature, dissolved oxygen(DO) levels, p H, radium iso...  相似文献   

云南烤烟低温冷害风险区划   总被引：1，自引：0，他引：1  

李蒙  张明达  朱勇  张茂松 《气象科学》2014,34(3):294-298

用云南93个烤烟种植县气象站1961—2010年4—9月逐日平均气温、逐日最低气温,逐月平均气温,平均最低气温资料结合各类型烤烟低温冷害指标,基于概率和强度结合权重指数,计算了各烤烟种植县的春季、夏季、秋初和全生育期综合低温冷害风险指数。使用低温冷害风险指数与海拔、纬度因子建立的空间推算回归模型,在ArcGIS 9.3平台下实现了低温冷害风险指数的空间精细化推算、订正及区划,进一步将其分类为5个风险等级,且对区划结果进行了分析。区划结果可为烤烟生产相关单位提供低温冷害防御的决策依据。  相似文献   

Soil saturation index of salt marshes subjected to spring‐neap tides: a new variable for describing marsh soil aeration condition     

Pei Xin  Badin Gibbes  Ling Li  Zhiyao Song  David Lockington 《水文研究》2010,24(18):2564-2577

Organized spatial distribution of plants (plant zonation) in salt marshes has been linked to the soil aeration condition in the rhizosphere through simplistic tidal inundation parameters. Here, a soil saturation index (ratio of saturation period to tidal period at a soil depth) is introduced to describe the soil aeration condition. This new index captures the effects of not only the tidal inundation period and frequency but also the flow dynamics of groundwater in the marsh soil. One‐dimensional numerical models based on saturated flow with the Boussinesq approximations and a two‐dimensional variably saturated flow model were developed to explore the behaviour of this new soil aeration variable under the influence of spring‐neap tides. Simulations revealed two characteristic zones of soil aeration across the salt marsh: a relatively well aerated near‐creek zone and a poorly aerated interior zone. In the near‐creek zone, soils undergo periodic wetting and drying as the groundwater table fluctuates throughout the spring‐neap cycle. In the interior, the soil remains largely water saturated except for neap tide periods when limited drainage occurs. Although such a change of soil aeration condition has been observed in previous numerical simulations, the soil saturation index provides a clear delineation of the zones that are separated by an ‘inflexion point’ on the averaged index curve. The results show how the saturation index represents the effects of soil properties, tidal parameters and marsh platform elevation on marsh soil aeration. Simulations of these combined effects have not been possible with traditional tidal inundation parameters. The saturation index can be easily derived using relatively simple models based on five non‐dimensional variables. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献