门源地倾斜异常的深入分析   总被引：1，自引：0，他引：1  

苏旭  马文静 《高原地震》1996,(4)

应用形态法、差分法、契氏拟合法对１９８４—１９９５年门源倾斜的资料做了系统的分析、总结，对其２００ｋｍ范围内的中强地震的震前异常进行了分析，发现在１９８６年门源６．４级、１９９０年共和７．０级地震前趋势性异常比较显著，且异常幅度大、持续时间长，而在一些５级左右地震前异常不明显。并且发现在中强地震前门源倾斜ＮＳ向有一个减速过程，这似与以往总结的震例有所区别。并在此基础上对门源倾斜的映震能力作了评价，且提出了未来一个时期的地震趋势。  相似文献   

贵州地质灾害趋势预测实践与探讨          下载免费PDF全文

杨森林  彭王星  张楠 《江苏地质》2013,37(1):155-158

通过对贵州地质灾害趋势预测中使用的GIS空间分析法成图技术方法,以2010年为例进行了预测分析与效果检验,为地质灾害防治工作提供了中尺度预警参考。就下一步以敏感性因子参数下的趋势预测方法进行了探讨,提出趋势预测在地质灾害预警体系中的作用与位置序列。  相似文献   

Recent Sea Level and Sea Surface Temperature Changes Along the Maldives Coast     

O. P. Singh  Tariq Masood Ali Khan  Fahmida Aktar  Majajul Alam Sarker 《Marine Geodesy》2013,36(4):209-218

Maldives, a South Asian small island nation in the northern part of the Indian Ocean is extremely vulnerable to the impacts of Sea Level Rise (SLR) due to its low altitude from the mean sea level. This artricle attempts to estimate the recent rates of SLR in Maldives during different seasons of the year with the help of existing tidal data recorded in the Maldives coast. Corresponding Sea Surface Temperature (SST) trends, utilizing reliable satellite climatology, have also been obtained. The relationships between the SST and mean sea level have been comprehensively investigated. Results show that recent sea level trends in the Maldives coast are very high. At Male, the capital of the Republic of Maldives, the rising rates of Mean Tidal Level (MTL) are: 8.5, 7.6, and 5.8 mm/year during the postmonsoon (October-December), Premonsoon (March-May) and southwest monsoon (June-September) seasons respectively. At Gan, a station very close to the equator, the increasing rate of MTL is maximum during the period from June to September (which is 6.2 mm/year). These rising trends in MTL along the Maldives coast are certainly alarming for this small developing island nation, which is hardly one meter above the mean sea level. Thus there is a need for careful monitoring of future sea level changes in the Maldives coast. The trends presented are based on the available time-series of MTL for the Maldives coast, which are rather short. These trends need not necessarily reflect the long-term scenario. SST in the Maldives coast has also registered significant increasing trend during the period from June to September. There are large seasonal variations in the SST trends at Gan but SST and MTL trends at Male are consistently increasing during all the seasons and the rising rates are very high. The interannual mode of variation is prominent both in SST as well as MTL. Annual profile of MTL along the Maldives coast is bimodal, having two maxima during April and July. The April Mode is by far the dominant one. The SST appears to be the main factor governing the sea level variations along the Maldives coast. The influence of SST and sea level is more near the equatorial region (i.e., at Gan). There is lag of about two months for the maximum influence of SST on the sea level. The correlation coefficient between the smoothed SST and mean tidal level at Gan with lag of two months is as high as ~ +0.8, which is highly significant. The corresponding correlation coefficients at Male with the lags of one and two months are +0.5 and +0.3, respectively. Thus, the important finding of the present work for the Maldives coast is the dominance of SST factor in sea level variation, especially near the region close to the equator.  相似文献   

Historical trends affecting accumulation of sediment and phosphorus in Lake Pepin,upper Mississippi River,USA     

David J. Mulla  Adam C. Sekely 《Journal of Paleolimnology》2009,41(4):589-602

This study was conducted to collect historical land use information that would help explain the historical patterns in accumulation of sediment and phosphorus in Lake Pepin documented by Engstrom et al. (J Paleolimnol, this issue). A wide range of historical factors including cropping systems, phosphorus applications from fertilizer and manure, human and animal populations, river flows and phosphorus discharges from waste water treatment plants were studied using statistical methods. Results showed that sediment losses from the Minnesota River basin are significantly correlated with historical increases in river flows, row crop production acreage and basin population. Total phosphorus accumulations in the sediments of Lake Pepin are significantly correlated with increased phosphorus discharges from metropolitan area wastewater treatment plants, and increases in row crop acreage and river flows. Total phosphorus inflows to Lake Pepin are significantly correlated with increases in river flows, row crop acreage and phosphorus fertilizer applied to agricultural lands. This is one of eight papers dedicated to the “Recent Environmental History of the Upper Mississippi River” published in this special issue of the Journal of Paleolimnology. D. R. Engstrom served as guest editor of the special issue.  相似文献   

Advances in separating effects of climate variability and human activity on stream discharge: An overview     

《Advances in water resources》2014

Separating effects of climate change (ΔQ^c) and human activity (ΔQ^h) on stream discharge at the watershed scale is needed for developing adaptive measures to climate change. However, information is scarce in existing literature regarding whether such separating is feasible and whether reliable results can be produced. The objectives of this overview were to: (1) compare currently-used methods; (2) assess assumptions and issues of the methods; and (3) present a generic framework that overcomes possible issues. Based on the overview of fifteen recent representative studies, two methods can be used to estimate absolute magnitudes of ΔQ^c and ΔQ^h, while another method can be used to distinguish relative magnitudes of ΔQ^c versus ΔQ^h only. Because the methods’ fundamental assumptions about baseline versus altered period, water storage change and deep groundwater loss, precipitation-runoff relationship, hysteresis influence of human activity, and record of time series can seldom be satisfied for many watersheds, it is more realistic and practical to distinguish relative effects than to estimate absolute magnitudes of ΔQ^c and ΔQ^h. Moreover, a generic framework was presented for gauged watersheds with negligible groundwater loss, aiming to avoid misuse of the methods in practice.  相似文献   

近50 a南京夏季降水的气候特征   总被引：6，自引：1，他引：5  

毛宇清  吴海英  裴海瑛  何鹏程  刘冬晴 《气象科学》2012,32(6):646-652

利用南京6站近50 a(1960—2009年)的夏季逐日降水资料,应用累积距平、趋势系数、小波分析等方法,分析了南京地区夏季降水和旱、涝年的时空特征。结果表明,南京地区夏季降水量、雨日、暴雨日和暴雨日降水强度均有明显的年代际变化特征,其中降水量和暴雨日数的年代际变化基本一致;各站夏季降水量、雨日和暴雨日均呈增加趋势,总降水量的增加趋势主要是大雨及以上量级降水的贡献;夏季降水量存在2～8 a的周期变化;南京地区旱、涝年的夏季降水量与长江中下游地区有较好的一致性,与华南地区呈相反关系。  相似文献   

Quantification of the magnitude of net erosion in the southwest Barents Sea using sonic velocities and compaction trends in shales and sandstones     

《Marine and Petroleum Geology》2017

During specific intervals within Mesozoic and Cenozoic times, several areas of the southwestern Barents Sea were subjected to uplift and erosion. Areas with missing shallow stratigraphic interval sections and major erosion can be seen at several places along interpreted regional profiles in the southwestern Barents Sea. A new Normal Compaction Trend (NCT) for two selected shale– and sandstone–dominated lithologies has been constructed based on sonic logs in the southwestern Barents Sea. The shale– dominated NCT is calibrated to the Cretaceous shales in the northern North Sea and Norwegian Sea and applied to the Cretaceous shales of the Barents Sea. The sandstone–dominated NCT is calibrated to the Lower Jurassic Åre Formation of the Norwegian Sea and applied to the Lower Jurassic–Upper Triassic coastal plain section in the Barents Sea. By utilising the NCT model, the study estimates net apparent erosion in 28 selected Barents Sea wells based on comparison of sonic log velocities. A net apparent erosion map of the study area was constructed by gridding of the well values. The accuracy of the map is limited in areas with little well control, such as in the northwest, where the east–west transition into the southwestern Barents Sea region is poorly constrained. With that in mind, the map clearly shows two regional trends which dominate the erosion pattern in the study area; an increasing amount of erosion towards the north and a sharp decrease of erosion westwards of the hinge zone into the southwestern Barents Sea. The highest erosion estimates are observed towards Svalbard, with values up to 2500 m. The results of this study can be further utilized in petroleum system studies in the eroded areas.  相似文献   

我国远洋渔业发展阶段特征、演进动因与趋势预测          下载免费PDF全文

刘芳  于会娟 《海洋开发与管理》2017,34(9):59-64

随着近海渔业资源的枯竭及近海养护政策的进一步实施,发展远洋渔业成为增加海水产品供给、改善居民膳食结构、实现我国渔业可持续发展的战略选择。文章回顾了新中国成立以来我国远洋渔业的发展历程:按照产量、产值、作业海域、远洋渔业产业结构等指标对其进行阶段划分,依次分为空白期(1949—1971年)、积极筹备期(1972—1984年)、起步期(1985—1990年)、快速发展期(1991—1997年)、调整期(1998—2006年)、优化期(2007年至今)6个阶段,并分析其阶段特征;发现国际渔业合作、远洋技术革新、近海渔业政策和政府补贴引导构成了远洋渔业不同阶段的演进动因。结合当前我国远洋渔业所处阶段的特征和国内外渔业环境,对我国远洋渔业的发展趋势进行预测,即我国远洋渔业发展趋势体现在如下三大转变,(1)由渔业资源依附型转变为科技资源驱动型;(2)资源消耗型转变成资源创造型,推进海外"蓝色粮仓"建设;(3)资源破坏型转变为资源养护型,树立负责任远洋渔业大国的形象。  相似文献   

对流层大气氧化性研究进展   总被引：2，自引：0，他引：2  

林云萍  赵春生 《地球科学进展》2009,24(5):488-496

对流层大气氧化性是对流层大气自我清洁能力的一个重要指标,对流层中大多数痕量气体都是通过氧化过程清除的.回顾近半个世纪以来对流层大气氧化性的研究历史,对流层大气氧化性的研究无论是从测量技术还是模式研究方面都已取得了一定的进展.工业革命以来,由于人类活动的影响,CO、NOx和碳氢化合物等大气污染物排放增多,使得全球对流层大气OH浓度呈下降趋势,未来对流层大气氧化性的变化很大程度上也取决于这些气体的排放情况.利用全球三维大气化学传输模式MOZART研究中国地区对流层大气OH自由基的分布和变化趋势表明,与全球OH自由基变化趋势不同,近10年来中国东部地区OH自由基浓度趋于增加.未来对流层大气氧化性研究的关键问题仍是OH自由基测量技术的提高问题,OH自由基观测结果是完善对流层光化学机制和改进大气化学模式的先决条件.  相似文献   

Trend analysis using nonhomogeneous stochastic diffusion processes. Emission of CO<Subscript>2</Subscript>; Kyoto protocol in Spain     

R. Gutiérrez  R. Gutiérrez-Sánchez  A. Nafidi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(1):57-66

In this study, we propose a methodology to analyse the gradual secular trends present in the time evolution of certain endogenous variables, which are of particular interest in environmental research. This methodology is based on modelling such variables by nonhomogeneous stochastic diffusion processes, the trend functions of which may be made to depend on other, exogenous, variables, which are controllable and which affect and model, in turn, the possible irregularities of such trends. The methodology is applied to analyse the evolution of the emission of CO₂ in Spain, and it is shown that the evolution of the Spanish GDP affects the trend component. These circumstances are considered in the context of Spain’s non-compliance with the Kyoto protocol on controlling the emission of greenhouse gases.  相似文献