华北地区强震前后的 h 值及“震情窗口”变化   总被引：1，自引：0，他引：1  

钱兆霞 《地震研究》1988,(3)

邢台、渤海、海城以及唐山大地震前1年内,围绕震中甚至距离震中500多公里的地区发生的某些震群,出现衰减系数异常(h≤1)。同时发生在林县、太原、长岛地区的小震群,其月频度几乎同步出现峰值。称林县、太原、长岛地区为“震情窗口”。强震前区域震情h值异常和“震情窗口”变化呼应,对判断未来强震三要素是有益的。  相似文献   

Isostatic status in North China (1)
Method and local compensation     

Rui Feng  Jun Wang  Shuzhen Zheng  Guifang Huang  Huifen Yan  Hainan Zhou  Ruoshui Zhang 《地震学报(英文版)》1988,1(4):73-84

Following Airy and Pratt principles, five kinds of local-compensation models are analysed and a rapid 3-D gravity formula is utilized to calculate isostatic anomalies for 66 models with different parameters. It is noted that isostatic gravity maps appear nearly identical in their main patterns and features. The optimum compensation model in North China is one of modified Airy models in which the different density distribution in the surface, upper crust and lower crust is taken into account and the standard crustal thickness is about 50km. The position of the complete compensation interface is located in the upper mantle. The North China platform as a whole is under sub-isostatic equilibrium status with an isostatic anomaly of about 18·10⁻⁵ m/s² on an average. The distribution of isostatic gravity anomaly shows an obvious blockwise pattern. Most positive anomaly areas occur over the eastern part, the Jiao-Liao Block, Mt. Yan block and northern margin of the Hebei-Shandong block, whereas a negative area occurs in the Shanxi graben. The comparison of models indicates that the Moho discontinuity is not suitable to be taken as a compensation interface, and the compensation effects in Airy model are better than that in Pratt model, which is consistent with the feature of dominant layered structure and less lateral inhomogeneity in crust. Some results about composite compensation, the basic characteristics of isostatic anomaly and deep stucture will be published later in the second part of this paper. Wang Bowen took part in some work in this paper.  相似文献   

Earth pillar formation on the Mountain Pine Ridge,Belize     

Mark Francek 《地球表面变化过程与地形》1988,13(2):183-186

The roadcuts of Belize's Mountain Pine Ridge feature numerous coarsely textured earth pillars less than 10 cm in height. Preferential impregnation of iron occurs over a buried pebble resulting in a dripline. The higher concentration of iron along the buried pebble's dripline is later oxidized and exposed to the surface by rainsplash erosion. For slopes greater than five degrees, the intensity of sheetwash erosion is great enough to remove pillars. Earth pillar genesis thus seems a function of laterization, slope angle, and sheetwash intensity.  相似文献   

Seasonal cycle of surface circulation in the coastal North Indian Ocean     

S R Shetye  S Satheesh Chandra Shenoi 《Journal of Earth System Science》1988,97(1):53-62

Monthly-mean winds and currents have been used to identify the driving mechanisms of seasonal coastal circulation in the North Indian Ocean. The main conclusions are: (i) the surface circulation off Arabia is typical of a wind-driven system with similar patterns of longshore current and wind stress; (ii) circulation off the west coast of India is consistent with the dynamics of a wind-driven eastern boundary current only during the southwest monsoon. During the northeast monsoon it is possible that the influence of the interior flow is important. (iii) There are at least three mechanisms that influence the surface circulation off the east coast of India: wind-stress, influence of fresh-water run off and contribution of the interior flow. It is difficult at present to assess the relative importance of these three processes.  相似文献   

Primary cracking of kerogens. Experimenting and modelling C₁, C₂–C₅, C₆–C₁₅ and C₁₅₊ classes of hydrocarbons formed     

J. Espitali  P. Ungerer  I. Irwin  F. Marquis 《Organic Geochemistry》1988,13(4-6)

Mathematical models of hydrocarbon formation can be used to simulate the natural evolution of different types of organic matter and to make an overall calculation of the amounts of oil and/or gas produced during this evolution. However, such models do not provide any information on the composition of the hydrocarbons formed or on how they evolve during catagenesis.From the kinetic standpoint, the composition of the hydrocarbons formed can be considered to result from the effect of “primary cracking” reactions having a direct effect on kerogen during its evolution as well as from the effect of “secondary cracking” acting on the hydrocarbons formed.This report gives experimental results concerning the “primary cracking” of Types II and III kerogens and their modelling. For this, the hydrocarbons produced have been grouped into four classes (C₁, C₂–C₅, C₆–C₁₅ and C₁₅₊). Experimental data corresponding to these different classes were obtained by the pyrolysis of kerogens with temperature programming of 4°C/min with continuous analysis, during heating, of the amount of hydrocarbons corresponding to each of these classes.The kinetic parameters of the model were optimized on the basis of the results obtained. This model represents the first step in the creation of a more sophisticated mathematical model to be capable of simulating the formation of different hydrocarbon classes during the thermal history of sediments. The second step being the adjustment of the kinetic parameters of “secondary cracking”.  相似文献   

Interannual Fluctuations of Surface Air Temperature over North America and Its Relationship to the North Pacific SST Anomaly     

Wu Renguang  Chen Lieting 《大气科学进展》1995,12(1):20-28

The characteristics of interannual fluctuations of the surface air temperature over North America are investigated by using the surface air temperature data of 130 stations during 1941 through 1980. It is found that the surface air temperature bears about ten-year time scale oscillation over the southeastern and northwestern North America and along the west coast of the United States, and it has the characteristics of quasibiennial oscillation over the eastern North America. The ten-year scale oscillation of the surface air temperature is related to that of the sea surface temperature (SST) of North Pacific through the PNA pattern atmospheric circulation anomaly over North Pacific through North America. It is shown that the North Pacific SST has a closer association with the surface air temperature over North America than the central and eastern equatorial Pacific SST. The characteristics of the seasonal variations of the relationship between the North Pacific SST and the surface air temperature over No  相似文献   

华北地震场和源地壳形变前兆研究   总被引：3，自引：1，他引：3  

何世海 《地震》1995,(3):199-207

文中用实测资料和构造物理学观点论证了华北中、强地震前孕震形变场(断层活动系统)的存在和它的运动学与力学机制,并用有限元法加以检验;讨论了形变场、源前兆之间的关系和它们的前兆特征;给出了可操作的剪切破裂指标S(t),用断层滑动速度和剪切应变速度较好地表达了某地的地震破裂危险性;最后,提出了华北形变场活动的长期稳定性和周期性(约12年)。  相似文献   

A Preliminary Study on the Probabilistic Estimation of Deaths from Future Earthquakes in North China     

Fu ZhengxiangCenter for Analysis  Prediction  SSB  Beijing  China 《中国地震研究》1995,(4)

During the period from 1800 to 1989,the degree of fatalities(?from earthquakes in North China(Lat.34.0°-42.0°N,Long.107.5°-125.0°E)varied exponentially with the frequency of earthquake events(N),namely:N=37.71 exp(-0.72?(E-logD,D:deaths).For the periods from 1988 to 1998 and from 1999 to 2009,the probabilities for earthquakes to cause one thousand or more deaths in North China are estimated to be 0.37 and 0.50,respectively,by using the Gumbel's extreme value theory.  相似文献   

华北型煤田矿井突水灾害的防治   总被引：5，自引：2，他引：5       下载免费PDF全文

王明玉  张宝柱 《地质论评》1995,41(6):553-558

我国华北型煤田矿井中具有多层含水层，常发生底板突水事件，为了对突水灾害的防治，本文提出了切实可行的步骤，并利用水力学概念模型，研究了该类型矿井的突水量规律及其防治方法。  相似文献   

Numerical simulation of the detachment dynamics in North China Basin     

张东宁  曾融生 《地震学报(英文版)》1995,8(4):511-517

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