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161.
陆相地层的层序地层学研究近年来取得了较大的进展,尤其在层序的组成、层序界线和最大洪泛面的识别以及层序模式的建立等方面研究得比较深入。层序地层的组成包括层序组合和层序的内部单元。层序界线和最大洪泛面的识别是陆相地层层序地层学研究的关键。目前已初步建立了箕状断陷盆地、坳陷盆地以及冲积地层背景的层序模式。 相似文献
162.
163.
采用b值时间扫描及地震复发周期等统计方法,对乌鲁木齐至沙湾一带1977年以来的地震观测资料进行了计算分析。初步结果表明:研究区域内5.0级以上中强地震发生前,b值均出现不同程度的负异常。利用地震复发周期计算公式和未来地震震级定量计算公式,得到区内不同震级区间的平均复发周期及今后2年左右可能发生的最大地震震级。 相似文献
164.
J. H. Barrett 《Stochastic Hydrology and Hydraulics》1992,6(3):151-165
An extreme value analysis of the flow of Burbage Brook is carried out by modelling peaks over a high threshold. The aims are to illustrate recently developed statistical techniques and to report on interesting features of the flow of the brook over a 58-year period. Peak flows are found to show marked seasonal variation and a downward trend. Then-year return level is estimated for various values ofn, and the reliability of the estimates is assessed. 相似文献
165.
An introduction to the
instrumonts to be used for solar radio observations in Beijing in Solar Cycle 23 is made
in this paper. They are 10cm solar radio telescope which has been used for a long time,and 1.0~2.0GHz,2.6~3.8GHz and 5.2~7.6GHz spectrometers. The former two spectrometers has
passed a test,showing
high guality,and the
5.2~7.6GHz one will
be in operation from 1999. It is believed that highl gualified data should be obtained in
the next solar cycle. 相似文献
166.
吉林大阳岔上寒武统凤山组—下奥陶统冶里组层序地层和化学地层研究 总被引:1,自引:1,他引:0
根据岩相序列、沉积、成岩作用特征,将吉林省大阳岔地区晚寒武世凤山期至早奥陶世冶里期层序地层分为6个三级层序,代表了6个三级海侵—海退旋回;与之相应,该时期碳酸盐岩δ13C值变化曲线出现5个低谷,其中凤山期至冶里早期泥晶灰岩δ13C值出现4次幅度较大的上升、下降飘移,而冶里中、晚期泥晶灰岩的δ13C值是在负值范围内波动。δ13C值低谷与层序界面和海退事件基本拟合。牙形类C.intermedius带下部海绿石质凝缩段是寒武纪末—奥陶纪初期最大海泛事件沉积,也是寒武纪与奥陶纪之交等时性的年代地层对比标志。 相似文献
167.
Joint estimation of transmissivity (T) and storativity (S) in a confined aquifer is done via maximum likelihood (ML). The differential equation of groundwater flow is discretized by the finite-element method, leading to equation t+x
t=u
t. Elements of matrices and , as well as estimated covariance matrix of noise termu
t, are functions of T and S. By minimizing the negative loglikelihood function corresponding to discretized groundwater flow equation with respect to T and S, ML estimators are obtained. The ML approach is found to yield accurate estimates of T and S (within 9 and 10% of their actual values, respectively) and showed quadratic convergence in Newton's search technique. Prediction of aquifer response, using ML estimators, results in estimated piezometric heads accurate to ±0.5 m from their actual, exact values. Statistical properties of ML estimators are derived and some basic results for statistical inference are given. 相似文献
168.
169.
A study of dissolved chromium in the St. Lawrence estuary and Gulf of St. Lawrence has been carried out. A chromium concentration of 0·7 μg l?1 was found in the St. Lawrence River. In the turbidity maximum of the upper estuary, chromium is removed from solution onto fine-grained resuspended sediments and internally produced organic-rich floccules. A simple flux calculation shows that these processes remove ~50% of the total dissolved chromium input of the river. At salinities greater than 5‰ dissolved chromium mixes conservatively. 相似文献
170.
The assessment of seismic hazard parameters is important in the seismically active regions. A straightforward approach is considered for the statistical estimation of the maximum values of earthquake hazard parameters. The Bayesian estimator is suggested and emphasis is given to the evaluation of the maximum possible Mmax (regional) magnitude in a future time interval T. This approach allows the uncertainty of earthquake magnitude to be accounted for. Seismic hazard parameters like the -value which is the slope of the magnitude-frequency law (where, b = loge) and the intensity (rate) of seismic activity and their uncertainties are also estimated. The quantiles of functions of distributions of true and apparent magnitude on a given time interval [0, T] are evaluated, as well. Two main assumptions are adopted for the method:(1) earthquake occurrence is Poissonian and(2) the magnitude-frequency law is of Gutenberg-Richter type with a cutoff maximum value of magnitude. It is needless to say the seismic catalog used must have a large number of events. This requirement leads to the estimation of the parameters referred to some of the most seismically active regions of the world, e.g., Chile, Peru-Equador-South Colombia,Central America and Mexico, which belong to the east part of the circum-Pacific belt. 相似文献