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61.
海洋可以被分成若干特征各异的、运动着的海水团,各种海洋现象就源于海水团的运动和相互作用。分隔不同海水团的前锋面上的混合作用是促使成矿组分发生沉淀富集的地球化学障。在海水团前锋混合带上,成矿组分在沉积物中产生同生富集,结果生成沉积矿床或矿源层。这是一种在时间上广泛发生但又尚未被人们所认识的崭新机制。 相似文献
62.
京西黄庄—高丽营断层西段晚更新世末的一次粘滑性活动 总被引:1,自引:0,他引:1
本文根据新近大比例尺地质图和探槽开控的结果,认为断层西段(仅在芦井至晓幼营间)晚更新世以来仍有明显活动,这种活动以正段倾滑运动为主,但兼具右旋走滑分量;并且在距今约2.4-2.1万年期间有过一次粘滑性活动,其垂直错距为0.91.0m;该段断层潜在有发生6-6.5级地震的可能性。 相似文献
63.
Fault interaction and seismicity: Laboratory investigation and its seismotectonic interpretation 总被引:2,自引:0,他引:2
Systems of two parallel linear faults of the same length with the angle of inclination =45° were investigated under uniaxial linearly increasing load. Perspex plates were used as models. For each treated fault configuration the morphology of tensile cracks and the sequence of seismoacoustic events of shear and tensile origin were studied.It is shown that the seismic regime of a fault system is strongly influenced by the contact conditions on a fault plane; it is different in the faults with the aseismic contact, represented by open slits, and in the faults with the seismoactive contact, represented by filled slits, respectively.The experiments proved the dominating role of a fast shear displacement of the stick-slip type in the regime of seismic energy release of a fault system. The tensile crack generation seems to be only of little—if not negligible—importance. On the other hand, the existence of tensile cracks in a fault system can play an important role in the course of subsequent loading cycles because the stick-slip displacements can take place not only along the primary faults but also along the planes of tensile cracks.A comparison of some results of model experiments and the already published results of geological and seismological investigations indicated that the way of seismic energy relase on faults in nature and in the laboratory could be of the same character. Several analogies between the seismic regime of a fault model and of real seismic regions were found concerning the morphology of faults, off-fault fore- and aftershocks, and earthquake doublets, respectively. 相似文献
64.
内蒙古东五分子地区韧性剪切变质作用的特征 总被引:6,自引:0,他引:6
东五分子地区花岗-绿岩地体经受了三种类型变质作用的改造。韧性剪切带不仅控制了区域变质岩组合的分布,而且也导致其变质作用的强度出现了逆转序列。根据岩石的结构、碎斑含量及矿物成分,韧性剪切变质岩划分为三类,其共同特点是具有碎斑结构。其变形结构分为单矿物型及组合型。同一块韧性剪切变质岩由处在单变平衡的一组矿物组成。根据岩石变形及重结晶的特点,结合其产状,确定出两种不同类型韧性剪切变质带。共生矿物对的研究证明它们形成于地壳不同深度及温度、压力条件。本区的金矿化、运移、沉淀与韧性剪切变质带紧密相关。 相似文献
65.
S. O. Zorina 《Stratigraphy and Geological Correlation》2007,15(3):267-276
The work is aimed at litho-, bio- and magnetostratigraphic subdivision of the Middle-Upper Jurassic sedimentary succession in the northeast of the Ul’yanovsk-Saratov depression (the East Russian plate). Problems of regional and interregional correlation of distinguished subdivisions are considered. As is shown, the ammonite biostratigraphy is most effective method for solving problems of chronostratigraphy. 相似文献
66.
Indian peninsular shield, which was once considered to be seismically stable, is experiencing many earthquakes recently. As
part of the national level microzonation programme, Department of Science and Technology, Govt. of India has initiated microzonation
of greater Bangalore region. The seismic hazard analysis of Bangalore region is carried out as part of this project. The paper
presents the determination of maximum credible earthquake (MCE) and generation of synthetic acceleration time history plot
for the Bangalore region. MCE has been determined by considering the regional seismotectonic activity in about 350 km radius
around Bangalore city. The seismotectonic map has been prepared by considering the faults, lineaments, shear zones in the
area and historic earthquake events of more than 150 events. Shortest distance from the Bangalore to the different sources
is measured and then peak ground acceleration (PGA) is calculated for the different source and moment magnitude. Maximum credible
earthquake found in terms of moment magnitude is 5.1 with PGA value of 0.146 g at city centre with assuming the hypo central
distance of 15.88 km from the focal point. Also, correlations for the fault length with historic earthquake in terms of moment
magnitude, yields (taking the rupture fault length as 5% of the total fault length) a PGA value of 0.159 g. Acceleration time
history (ground motion) and a response acceleration spectrum for the corresponding magnitude has been generated using synthetic
earthquake model considering the regional seismotectonic parameters. The maximum spectral acceleration obtained is 0.332 g
for predominant period of 0.06 s. The PGA value and synthetic earthquake ground motion data from the identified vulnerable
source using seismotectonic map will be useful for the PGA mapping and microzonation of the area. 相似文献
67.
WenJun Zhang 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(6):729-735
This study aimed to evaluate effectiveness and performance of several supervised neural network models and make pattern recognition
on invertebrate habitat zones. Probabilistic, general regression, and linear neural networks, and discriminant analysis were
used to recognize both known and unknown invertebrate habitat zones. The results showed that neural network models were better
than traditional discriminant analysis in the recognition of known habitat zones. There was not distinctive variation in recognition
from different neural network models. Sensitivity analysis indicated that the learning rate of the neural network would influence
recognized results. An unknown invertebrate species from Lepidoptera was recognized to be soil-dweller (dryland) by both neural
network models and discriminant analysis. In sensitivity analysis it was additionally recognized to be the type of plant canopy
(terrestrial). Overall the species was estimated to be a soil-dweller (dryland) or live on plant canopy (terrestrial). It
was concluded that neural network models can perform better than conventional statistic models in pattern recognition, but
a comprehensive comparison among various models is necessary in order to achieve a high reliable recognition and prediction.
Furthermore, sensitivity analysis can lead to an in-depth grasp on the mechanism in the recognition and is thus needed. 相似文献
68.
中国陆地生态系统脆弱带遥感模型 总被引:4,自引:0,他引:4
本研究通过对我国陆地生态系统8个典型样地的植被指数取样实验和图像计算结果发现,这8个样地植被指数随着水、热因子的季节变化,在时间和空间上具有一定的“绿波推移”和“景观更替”规律。在中国东部湿润的季风区(样地1-3),随着纬度的增高,其月平均植被指数与月平均气温有较大的相关。发现降水相对丰沛的地带,热量和光照条件的变化成为植被生长和变化的自然限制因子;而在中国北方森林-森林草原-典型昌原-荒漠草原-荒漠地带上,随着从东部(湿润地区)到西部(干旱地区)干湿条件的更替,月平均植被指数与降水多寡有较大的正相关关系。在8个样地上都呈现出共同的规律,即定向风的分布与植被指数的分布在时间和空间上具有逆相分布的“套合关系”。尤其在时间上有相逆套合关系,这正是中国北方沙尘暴和沙漠化加剧的自然原因。本研究定量地给出了我国陆地不同经纬度带生态系统脆弱季节和累积时间的分布。 相似文献
69.
提出了利用地面重力异常数据计算地面扰动位径向二阶梯度时,远距离带区影响的误差公式,结果以级数形式给出,以其数学模型为基础,利用全球重力位模型GPM98,计算确定了不同平均异常网格大小情况下截断半径取一系列值时的远区影响,在将卫星重力梯度和航空重力梯度观测数据与地面重力数据进行联合处理时,文中提出了远区影响的数量关系,对于确定合理的截断半径大小具有一定的参考价值。 相似文献
70.