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云南普洱地区6级以上地震前的Y值异常特征 总被引:1,自引:0,他引:1
本利用加卸载响应比方法研究了云南省普洱地区ML6.0级以上地震前的加卸载响应比随时间的变化,计算了这个地区近期的加卸载响应比,结果显示,普洱地区6级以上地震前Y值出现明显异常,近期的Y值显异常,表明该地区或在以其为中心方圆100-200公里的区域内在1995年或稍长时间内发生6.0级以上的地震的可能性很大。 相似文献
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以地球介质参数尾波Q(-1)作为响应,给出了加卸载响应比Y(Q-1)的计算公式。利用美国南加州地区频率分别为1.5Hz,3.0Hz,6.0Hz,12.0Hz,24.0Hz等5个频段的尾波Q数据,研究了美国北岭地震(199年1月17日,Mw6.7)前后的加卸载响应比Y(Q-1)随时间的变化。结果表明,除频率为12.0Hz这一频段外,其它频段的加卸载响应比Y(Q-1)在震前都有不同程度的变化,其中频率为24.0Hz的Y(Q-1)在1993年明显升高。震后各频段的Y(Q-1)趋于正常。 相似文献
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以地球介质参数尾波Q^-1作为响应,给出了加卸载响应比YQ-1的计算公式。利用美国南加州地区频率分别为1.5Hz,3.0Hz,6.0Hz,12.0Hz,24.0Hz等5个频段的尾波Q数据,研究了美国北岭地震(1994年1月17日,Mw6.7)前后的加卸载响应比YQ-1随时间的变化。结果表明,除频率为12.0Hz这一频段外,其它频段的加卸载响应比YQ-1在震前都有不同程度的变化,其中频率为24.0H 相似文献
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加卸载响应比在Poisson模型下的随机分布 总被引:9,自引:2,他引:7
本文在地震的发生时间服从Poisson过程,而地震震级服从Gutenberg-Richter关系的前提下,对不同定义的加卸载响应比Y值的随机分布进行了探讨。结果表明:当在计算窗口的地震发生的期望数目较大(〉40)时,Y1 ̄Y5值的分布基本稳定,出现高加卸载响应比的概率极低。然而当计算窗口的地震期望数目过小时,Y2 ̄Y5值则变得不太稳定。也就是说,服从Poisson过程的地震序列,在计算窗口的地震期 相似文献
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中国大陆地区中强地震前加卸载响应比异常时间尺度的统计研究 总被引:4,自引:2,他引:4
加卸载响应比理论是近年来提出的地震预测方法。本文进行了加卸载响应比异常时间尺度的统计研究,其中包括中国大陆地区5.0~8.1级的部分中强地震共30个震例,并得出加卸载响应比异常的时间尺度与未来地震震级之间的拟合函数。结果表明,地震前加卸载响应比异常的时间尺度与未来地震的震级具有正变关系,即震级越高,地震前加卸载响应比异常的时间尺度越长。根据加卸载响应比异常的时间尺度与震级之间的关系可以估计未来地震的发震时间,同时,可以确定加卸载响应比时空扫描过程中时问长度的大小。 相似文献
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Seasonal and annual trends of changes in rainfall, rainy days, heaviest rain and relative humidity have been studied over the last century for nine different river basins in northwest and central India. The majority of river basins have shown increasing trends both in annual rainfall and relative humidity. The magnitude of increased rainfall for considered river basins varied from 2–19% of mean per 100 years. The maximum increase in rainfall is observed in the Indus (lower) followed by the Tapi river basin. Seasonal analysis shows maximum increase in rainfall in the post‐monsoon season followed by the pre‐monsoon season. There were least variations in the monsoon rainfall during the last century and winter rainfall has shown a decreasing trend. Most of the river basins have experienced decreasing trends in annual rainy days with a maximum decrease in the Mahanadi basin. The heaviest rain of the year has increased from 9–27 mm per 100 years over different river basins with a maximum of 27 mm for the Brahamani and Subaranrekha river basins. A combination of increase in heaviest rainfall and reduction in the number of rainy days suggest the possibility of increasing severity of floods. Such information is useful in the planning, development and management of water resources in the study area. Further, the majority of river basins have also experienced an increasing trend in relative humidity both on seasonal and annual scales. An increase in annual mean relative humidity for six river basins has been found in the range of 1–18% of mean per 100 years, while a decrease for three river basins from ? 1 to ? 13% of mean per 100 years was observed, providing a net increase in the study area by 2·4% of mean per 100 years. It is understood that an increase in areal extent of vegetation cover as well as rainfall over the last century has increased the moisture in the atmosphere through enhanced evapotranspiration, which in turn has increased the relative humidity. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Although changes in rainfall characteristics have been noted across the world, few studies have reported those in mountainous areas. This study was undertaken to clarify spatial and temporal variations in rainfall characteristics such as annual rainfall amount (Pr), mean daily rainfall intensity (η), and ratio of rain days (λ) in mountainous and lowland areas in Taiwan. To this aim, we examined spatial and year‐to‐year variations and marginal long‐term trends in Pr, η, and λ, based on rainfall data from 120 stations during the period 1978–2008. The period mean rainfall () at the lowland stations had strong relationships with the period mean daily rainfall intensity () and the period mean ratio of rain days () during those 31 years. Meanwhile, was only strongly related to at mountainous stations, indicating that influences on spatial variations in were different between lowland and mountainous stations. Year‐to‐year variations in Pr at each station were primarily determined from the variation in η at most stations for both lowland and mountainous stations. Long‐term trend analysis showed that Pr and η increased significantly at 10% and 31% of the total 120 stations, respectively, and λ decreased significantly at 6% of the total. The increases in Pr were mostly accompanied by increases in η. Although stations with significant η increases were slightly biased toward the western lowland area, increases or decreases in Pr and λ were not common. These results contribute to understanding the impacts of possible climate changes on terrestrial hydrological cycles. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Phosphorus dynamics in water and sediments in urbanized and non-urbanized rivers in Southern Brazil 总被引:1,自引:0,他引:1
Pagliosa PR Fonseca A Bosquilha GE Braga ES Barbosa FA 《Marine pollution bulletin》2005,50(9):965-974
Phosphorus flux models show that the removal tends to be a common feature in polluted estuarine systems whereas the release of P to the adjacent coastal area occurs in pristine environments. This study analyzes the distribution of P in water and sediments along six rivers in the south coast of Brazil. Three rivers located inside protected areas were considered non-polluted and used as a control of urbanization. The other three, situated within urbanized areas, were considered as having highly elevated concentrations of P. Results showed a different behavior of P in water and sediments located in urbanized and non-urbanized areas. The concentrations of dissolved organic (P-org) and inorganic (P-inorg) phosphorus in water, and the total phosphorus (P-tot) and polyphosphate (P-poly) in sediments where higher in the urbanized rivers compared to the non-urbanized ones. Both P of punctual origin and of diffuse origin contributed to the maintenance of elevated concentrations and disturbed the natural fluxes along the polluted rivers. The minimum and maximum concentrations in urbanized areas varied from 0.39 to 12.45 (microM) for P-org and 0.00 to 5.92 (microM) for P-inorg in water, and in sediments from 89.90 to 808.16 (microM g(-1)) for P-tot and 0.00 to 76.51 (microM g(-1)) for P-poly. In non-urbanized areas concentrations in water varied from 0.22 to 1.20 (microM) for P-inorg and 4.43 to 5.56 (microM) for P-org, and in sediments from 45.91 to 652.26 (microM g(-1)) for P-tot and 0.00 to 8.61 (microM g(-1)) for P-poly. Using a hierarchical sampling design and a simple model of variation of P (K(d) model) it was possible to demonstrate that urbanized and non-urbanized estuaries may act as sinks or sources of P. The variation of P analysis in different points along each of the six rivers showed that release and removal areas may occur within a same river independently of its urbanization. 相似文献
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Jurassic and Lower Cretaceous radiolarian zonation in Japan and in the western Pacific 总被引:7,自引:0,他引:7
Abstract A radiolarian zonal scheme for the entire Jurassic and Lower Cretaceous using biostratigraphic data from both Japanese Island sections and the western Pacific seafloor is documented. The zonation is applicable to low and middle paleolatitude portions of the Paleo-Pacific ocean. Radiolarian bio-events such as the evolutionary first appearance biohorizon, first occurrence biohorizon, and last occurrence biohorizon were used to define zones. The 11 zones proposed are, in ascending order, Parahsuum simplum, Trillus elkhornensis, Laxtorum(?) jurassicum, Tricolocapsa plicarum, Tricolocapsa conexa, Stylocapsa(?) spiralis, Hsuum maxwelli, Pseudodictyomitra primitiva, Pseudodictyomitra carpatica, Cecrops sep-temporatus, and Acanthocircus carinatus zones. Preliminary age assignments for these zones are presented. 相似文献
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This Special Issue of Earth Surface Processes and Landforms develops from the ‘Geomorphology: a 2020 Vision’ Annual Conference of the British Society for Geomorphology, organised at the University of Birmingham, UK, in July 2007. Entitled ‘New Developments in Process Understanding and Modelling in Geomorphology’, the Issue comprises a vibrant selection of 10 ‘process’ papers from leading researchers in geomorphological processes who presented at Birmingham. It aims to provide a readily accessible source of new and emerging ideas in understanding different landform processes across a range of space and time scales, based on innovations in geomorphological modelling and monitoring. The last few years have seen significant and exciting changes in geomorphology, especially in conceptual developments, numerical simulations, monitoring methodologies, data‐acquisition strategies and dating techniques. The resultant empirical datasets, theory development and modelling results have generated substantial advances in the understanding of geomorphological processes, form‐process feedbacks, scale impacts, long‐term landform evolution, the effects of climate and environmental change, and human impacts and management strategies. The Special Issue attempts to address the following key challenges: (a) to build on our Conference theme ‘Geomorphology: a 2020 Vision’, by identifying fundamental areas where doors need to be opened, for example in theory development, conceptual understanding, model evaluation, integration of the chemistry, physics, biology and mathematics of geomorphological processes, experimental validation, data needs and monitoring requirements; (b) to look forward to the next decade and beyond, and critically examine some of the approaches we will need for the questions ahead; and (c) to stimulate new research in the geomorphological sciences by highlighting both research gaps and promising developments, including emerging process modelling approaches, monitoring technologies and robust datasets. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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本文对中国石油、天然气资源作了重点的介绍.强调了这些资源对我国国民经济和国防建设的重要性.目前,我国油气资源短缺的现象日益严重.作者指明了在前第三纪海相残留盆地中勘探这些资源,会带来光明的前景. 相似文献
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