利用精定位小震资料反演1933年叠溪M7?地震震源断层面参数     

李峰  张效亮  贾启超  刘华国  龚飞 《震灾防御技术》2017,12(3):565-573

1933年叠溪发生7?级强震，关于此次地震的发震构造存在较大争议，有些学者认为NW向松坪沟断裂是此次地震的发震构造，另有学者认为近NS向岷江断裂南段才是这次地震的发震构造。本文根据成丛小震发生在大震断层面附近的原则，利用1990-2014年精定位小震目录，根据万永革等（2008）提出的震源断层面拟合方法，反演了叠溪地震震源断层走向、倾角和位置。断层走向和倾角分别是172.8°和82.9°，倾向偏向西。本文结果更支持岷江断裂南段为叠溪地震发震构造这一结论。  相似文献   

A comparison of stream water temperature regimes from open and afforested moorland,Yorkshire Dales,northern England     

L. E. Brown  L. Cooper  J. Holden  S. J. Ramchunder 《水文研究》2010,24(22):3206-3218

Despite the known importance of water temperature for river ecosystems, the thermal regime of streams and rivers can be heavily modified by afforestation. Although the nature of the heat budget affecting streams in forested catchments shows high variability in space and time, most of the studies of stream temperature response to afforestation have lacked replication among streams. This study examined the impacts of coniferous forest plantations on stream water temperature at six sites (three forested and three open moorland) in the Yorkshire Dales, northern England. Our aim was to test the hypothesis that afforestation would alter the thermal regime of streams, leading to reduced year‐round thermal variability, and cooler summer/warmer winter water temperatures, relative to streams flowing across open moorland. Data collected from April 2007 to March 2009 showed similar thermal dynamics among all six streams over the study period, although variability in forested streams was markedly lower as expected. Mean and maximum daily water temperatures were significantly higher in open moorland streams for much of the year but while some forested streams were warmer than individual moorland streams during winter months (November to February), there was considerable overlap in water temperature between moorland and forest streams. Most stream temperature records showed evidence of low/no winter flow and freezing. These results contrast with many previous studies that have reported warmer temperatures in forested versus open moorland streams during winter, a finding that most likely reflects site‐specific hydrological, geomorphological and climatological influences on water temperature in addition to afforestation. This study demonstrates the need for replication of hydrological monitoring when examining the effects of basin‐scale management practices and provides further evidence for changes in stream thermal regime following afforestation, a practice that is likely to increase in future due to growing demands for increased forest cover in the UK uplands. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

岩溶水型水源地保护区划分方法研究——以济南市曹楼水源地为例          下载免费PDF全文

王金晓  陈奂良  滕跃  高菡  张文强  张翼飞 《山东国土资源》2022,38(6)

对地下水水源地进行保护区划分将提高地下水的安全保障程度。岩溶水型水源地由于含水层的非均质、各向异性的特点,难以合理准确的划分水源地保护区。以济南市曹楼水源地为研究对象,在充分收集和分析水源地水文水质、地形地貌等资料的基础上,采用组合法划定水源地保护区,结合地形地质条件对保护区范围进行修正,保护水源地免受污染。利用组合法划分的水源地保护区加强了对上游补给区,尤其是地下水主径流带的保护,划分结果更符合实际。利用该方法能提高对水源地主要补给区的保护,保障地下水的可持续开发利用,为水源地的保护提供科学的依据和参考。  相似文献   

东海区小黄鱼渔业生物学现状的分析   总被引：15，自引：1，他引：15  

林龙山  程家骅 《中国海洋大学学报(自然科学版)》2004,34(4):565-570

以2001年东海区渔业资源监测调查资料为依据，对小黄鱼的体长、体重、生长、死亡等渔业生物学特征及临界年龄等进行了分析研究。结果表明，目前东海区小黄鱼优势体长组为110～130mm，占41．34％；优势体重组为20～40g，占50．91％；总死亡系数为2．05，自然死亡系数为0．58，捕捞死亡系数为1．47，临界年龄为2．18龄。对照东海区小黄鱼生物学特征的历史状况分析，目前东海区小黄鱼个体小型化、低龄化、性成熟提早现象明显，生物学参数发生较大变化。建议在东海区现行资源状态下，小黄鱼的可捕标准应充分考虑其生物学现状加以科学调整。  相似文献   

The target strength of Antarctic krill (Euphausia superba) measured by the split-beam method in a small tank at 70 kHz     

Amakasu  Kazuo; Furusawa  Masahiko 《ICES Journal of Marine Science》2006,63(1):36-45

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关于修改港工钢筋混凝土规范小偏心受压构件正截面强度计算的建议     

王清湘 《海洋工程》1995,(2)

本文提出在小偏心受压构件正截面强度计算中，取消弯曲抗压强度ｆｃｍ（Ｒｗ），采用轴心抗压强度ｆｃ，这与构件的实际破坏形态相符。对小偏心受压构件正截面强度计算提出了设计建议。特别是对工程上大量应用的矩形截面对称配筋小偏压构件提示了简捷的设计方法，与以往的近似计算方法相比具有物理概念明确，精度高，方法简捷的特点。  相似文献   

Spatio-temporal variability of small copepods (especially Oithona plumifera) in shallow nearshore waters off the south coast of South Africa   总被引：1，自引：0，他引：1  

Francesca Porri  Christopher D. McQuaid  William P. Froneman 《Estuarine, Coastal and Shelf Science》2007,72(4):711-720

Although small copepods are one of the main dietary sources for many commercially important fish, their role in the pelagic trophic dynamics has traditionally been underestimated due to the methodology commonly used in plankton sampling. Temporal variation in abundance of adults and nauplii of small copepods (particularly Oithona plumifera) in nearshore waters on the south coast of South Africa was investigated fortnightly over 14 months at site (km) and location (100 m) scales. Sampling was within <500 m of the shore, where depth was ca. 10 m, using vertical hauls of an 80-μm mesh plankton net from 1 m above the seabed to the surface. Twenty-seven adult copepod taxa were recorded, but Oithona spp. was consistently the most abundant. Taxon richness was 7–19 on each sampling occasion. There was strong temporal variation (Oithona varied between 0 and 2300 m⁻³), but much of this was short-term variability (e.g. between consecutive sampling sessions), with no seasonality or other long-term discernable patterns. There were periods of consistently low numbers, but very high numbers often followed samples with low abundances. Nor was there spatial structure at the location scale, though numbers differed between sites. Despite considerable variability at the location scale within sites, Kenton consistently showed higher densities than High Rocks. Separate analyses, with Bonferroni adjustment, showed that this difference was significant on eight out of 21 occasions for Oithona, six for other pelagic copepods and three for nauplii. This suggests that hydrodynamics favour aggregation of plankton at Kenton. A high degree of short-term variability, with a tendency for aggregation of small zooplankton at certain sites has implications for both pelagic processes and food-web links between the benthic and pelagic environments.  相似文献   

Upstream migration and reproductive patterns of a population of allis shad in a small river (L'Aulne, Brittany, France)   总被引：2，自引：0，他引：2  

Acolas  M.L.; Veron  V.; Jourdan  H.; Begout  M.L.; Sabatie  M.R.; Bagliniere  J.L. 《ICES Journal of Marine Science》2006,63(3):476-484

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Wave-Current Forces on Small Square Cylinders (Part I)     

Li Yucheng  He Ming Professor  Dalian University of Technology  Dalian Former master student  Dalian University of Technology  Dalian 《中国海洋工程》1994,(3)

-Based on the extended Morison Equation and model tests, the in-line forces on small square cylinders caused by waves (regular and irregular) and currents are analyzed in detail in this paper. The hydrodynamic coefficient CD and Cu related to KC number and the effect of direction of wave incidence are also given, which can be used in engineering practice.  相似文献   

小直径组合桩的波浪力实验分析   总被引：2，自引：1，他引：2  

王爱群  徐立论 《海洋湖沼通报》2002,(1):9-17

本文给出小直径孤立桩、两个桩和2×2个桩的波浪作用力实验结果。在波浪水槽中以0°,45°,90°三个波浪方向测量了各桩所受的纵向力和横向力,文中讨论了组合桩之间的干扰效应,给出了干扰系数随KC数和桩距的变化。  相似文献