广州近35年来的气候变化   总被引：13，自引：0，他引：13  

周国逸  黄忠良 《热带地理》1999,19(3):198-203

在经过双累积曲线的严格验证后, 对１９６１ ～１９９５ 年广州的气象观测数据进行分析, 发现近３５年来广州年平均气温上升了０６２ ℃, 最为明显的时期是１９８５ ～１９９５ 年。１９８５ 年以前, 年平均气温年际间变化有较为明显的周期性, 周期长大约为７ ～８ 年。引起年平均气温上升的主要原因是湿季气温的明显上升, 这与湿季多云、空气湿度大和空气中烟尘含量增加等多方面因素的积加作用有关。年平均日照百分率有非常明显的下降趋势, １９９５ 年比１９６１ 年下降了２７９ ％ 。干湿季分别为２２９ ％ 和３２１ ％ , 干季日照百分率的降低主要发生在１ ～３ 月份。大气相对湿度也有下降的趋势, 但在不同时期是不一样的, 呈现二次曲线型的变化方式  相似文献   

Tectonic stress field in the epicentral zone of the Latur earthquake of 1993     

S. V. Srirama Rao  K. B. Chary  T. N. Gowd  F. Rummel 《Journal of Earth System Science》1999,108(2):93-98

In situ stress measurements by hydraulic fracturing were carried out in the 617 m deep borehole specially drilled in the epicentral zone of the 1993 Latur earthquake for the purpose of research. The stress measurements carried out at 592 m depth in this borehole are the deepest of all such measurements made so far in the Indian shield. The maximum and minimum principal horizontal stresses (S _H max andS _h min) have been derived from the hydrofracture data using the classical method. TheS _{H max} andS _h min are found to be 16.5 and 9.6 MPa at 373 m depth, and 25.0 and 14.1 MPa at 592 m depth, indicating that the vertical gradients ofS _hmax andS _hmin in the epicentral zone are 39 MPa/km and 21 MPa/km respectively. The principal horizontal stresses in the epicentral zone are comparable with those at Hyderabad and 30% higher than in most other comparable intra-continental regions. Analysis of the results indicate that the stresses in the focal region of the 1993 Latur earthquake have not undergone any significant change following its occurrence and this is in agreement with a similar inference drawn from the seismic data analysis. It appears that the Latur earthquake was caused due to rupturing of the overpressured fault segment at the base of the seismogenic zone.  相似文献   

Separation of dwarf and giant stars with ROTSE–IIId     

S. Bilir  T. Güver  M. Aslan 《Astronomische Nachrichten》2006,327(7):693-697

136 stars which were known to be members of the open cluster NGC 752 were observed at the R band with the ROTSE–IIId telescope located at the Turkish National Observatory (TUG) site. The data had been evaluated together with BV and 2MASS photometric data. A new practical method for separating dwarf and giant was described and applied. Evaluating the colour magnitude–diagrams with Padova isochrones revealed for the open cluster NGC 752 a metallicity similar to the Sun and an age of 1.41 ± 0.20 Gyr. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

区域数字地震台网近距离面波震级MS的测定     

陈祥熊  杨贵  傅再扬  陈文明 《地震》2002,22(2):53-59

使用福建区域数字台网7个宽带台观测到的47个发生于台湾地区的浅源强震(M_S ≥ 5)的近距离面波记录,量算了水平向乐夫波的最大合成振幅及震中距离,测定了所有这些强震的近距离面波震级MS。并将结果与国家台网公布的远距离平均MS震级进行比较和统计分析。结果表明,近距离测定的面波震级比远距离测定的M_S 有较大偏差。震级越小、距离越近,差异越大。对于区域地震台网测定的M_S 震级,需要做必要的修正,才能使其测定结果尽可能接近于国家台网公布的平均M_S 震级。文中还讨论了近距离和远距离面波震级测定差异的原因,及其修正办法。可供区域数字宽带台网速报本区域发生的近距离强震面波震级时参考。  相似文献   

An analysis of non-normal Markovian extremal droughts     

T. C. Sharma 《水文研究》1998,12(4):597-611

In many arid and semi-arid environments of the world, years of extended droughts are not uncommon. The occurrence of a drought can be reflected by the deficiency of the rainfall or stream flow sequences below the long-term mean value, which is generally taken as the truncation level for the identification of the droughts. The commonly available statistics for the above processes are mean, coefficient of variation and the lag-one serial correlation coefficient, and at times some indication of the probability distribution function (pdf) of the sequences. The important elements of a drought phenomenon are the longest duration and the largest severity for a desired return period, which form a basis for designing facilities to meet exigencies arising as a result of droughts. The sequences of drought variable, such as annual rainfall or stream flow, may follow normal, log-normal or gamma distributions, and may evolve in a Markovian fashion and are bound to influence extremal values of the duration and severity. The effect of the aforesaid statistical parameters on the extremal drought durations and severity have been analysed in the present paper. A formula in terms of the extremal severity and the return period ‘T’ in years has been suggested in parallel to the flood frequency formula, commonly cited in the hydrological texts. © 1998 John Wiley & Sons, Ltd.  相似文献   

最大卓越周期估算震级方法的优化研究          下载免费PDF全文

(赵庆旭  王延伟  刘娟  莫红艳  曹振中) 《世界地震工程》2023,39(2):200-212

震级估算是地震预警系统(EEWs)的核心任务。基于最大卓越周期参数(^p_max)的震级估算方法被广泛研究和应用,但^p_max计算细节被忽视,导致^p_max的震级估算效果存在较大的差异。为此,利用日本的大量井下强震记录,对^p_max计算涉及的滤波范围、滤波阶数和平滑系数的设置进行优化,提出了^p_max的优化计算方法,即滤波范围选用高通0.001 Hz,滤波阶数为1阶,平滑系数取0.95。利用日本和智利的初至3～6 s P波对比分析优化后的^p_max和优化前的^p_max以及_c的震级估算效果,结果表明:优化后的^p_max与震级的相关性和震级估算的误差均好于优化前的^p_max和_c。本文给出的^p_max优化计算方法,可以显著地改善^p_max在EEWs中的震级估算效果。  相似文献   

FREQUENCY AND MAGNITUDE OF BEDLOAD TRANSPORT IN A MOUNTAIN RIVER     

DOROTHEA GINTZ  MARWAN A. HASSAN  KARL-HEINZ SCHMIDT 《地球表面变化过程与地形》1996,21(5):433-445

Magnitude and frequency of bedload transport was examined in the Lainbach River, Bavaria, using magnetically tagged particles. During the study, 18 small to moderate events and one major event occurred. About 1 per cent of the flow period exceeded the entrainment threshold and at least once every year about 50 per cent of the tagged particles were mobile. Themajor event which occurred during the study period resulted in the deposition of a thick layer of sediment in parts of the channel and passive burial of most of the recovered particles. The step–pool pattern, which characterized the study site prior to the large event, was obliterated. However, the channel recovered quickly and has returned to a new step–pool pattern. The event changed the boundary conditions by increasing the availability of loose sediment and creating higher river-bed slopes in reaches between breached check dams. As a result, movement of individual particles measured for events of both the same magnitude and duration, occurring before and after the large event, yielded different values. For events which occurred after the large event, the range and the mean distance of movement were about ten times higher.  相似文献   

地震总输入能量与瞬时输入能量谱的研究   总被引：2，自引：0，他引：2  

刘哲锋  沈蒲生  胡习兵 《地震工程与工程振动》2006,26(6):31-36

现有的抗震设计理论大多是基于承载力或强度的设计方法,与其相应的反应谱理论最大的缺陷是无法反映地震动持时的影响,而以地震动能量作为设计参数时就能弥补现有抗震理论的不足。本文按照反应谱理论的思路建立了线性单自由度体系的地震动总输入能量谱和瞬时输入能量谱。研究发现,阻尼比为5%时的地震动总输入能量谱和最大瞬时输入能量谱的等价速度谱可以分别用阻尼比为0.5%和10%下的拟速度谱来近似获得;地震波的V/A值大于0.15时,总输入能量谱的Δt谱峰值与地震波的强震持时呈线性增长关系,V/A值小于0.15时,两者间的关系无规律性。最大瞬时输入能量谱的Δt谱峰值基本不受地震波的V/A值与强震持时的影响;输入能量谱(总输入能量谱与最大瞬时输入能量谱)的特征周期随地震波V/A值的增大而增大,根据分析结果本文提出了线性单自由度体系输入能量谱的简化计算方法,方法简便,计算结果偏安全。  相似文献   

2020年前中国大陆发生7级以上大地震频次和最大震级预测的初步研究   总被引：1，自引：1，他引：0  

傅征祥  丁香  王晓青 《地震》2006,26(1):35-39

应用多重贝努利独立试验模型, 研究2006～2020年间大陆发生7级以上大地震的频次及其概率, 以及最大震级的预测问题。 研究结果表明, 2006~2020年间大陆发生7.0～7.9级和7.5～7.9级大地震1次以上的概率为1.00, 发生8级大地震1次以上的概率为0.67, 或者说其间肯定会发生7级大地震, 而发生10次7.0～7.9级和1次7.5～7.9级大地震的可能性最大。 若按超过概率水平0.10而论, 发生7.0～7.9级地震最少发生 8次, 最多发生 12次; 发生7.5～7.9级地震为1～4次, 发生1～2次8.0～8.9级大地震可能性最大。 2020年前中国大陆发生最大地震的震级可能为7.5~7.9级。 不排除发生 8级地震的可能。  相似文献   

柴达木盆地东北部哈勒腾河流域风况特征及其对风沙地貌发育的影响   总被引：1，自引：0，他引：1  

田敏  钱广强  杨转玲  罗万银  逯军峰 《中国沙漠》2021,41(1):1-9

风况是影响风沙地貌发育的重要因子,在一定程度上决定了沙丘类型.为探究区域风沙地貌发育与风况之间的关系,对哈勒腾河流域不同区域一个完整年度的风况进行分析.结果表明:流域年平均风速为2.78 m·s-1,起沙风集中在春夏季,平均风速为7.78 m· s-1,起沙风事件平均持续时间为4.1 h;流域输沙势122-254 VU...  相似文献