1993, 15(1):1-10.
Abstract:The multifractal dimensions of spatial and temporal distribution of earthquakes in North China area and Northwest China area are calculated in this paper according to the definition of multifractal dimensions. The results show that the multifractal dimensions of seismic space and time distribution can describe the orderliness of spatial and temoporal distributin of earthquakes satisfactorily. Generally, obviously anomalous changes of multifractal dimension Dq, especially of high order, are found, and the curve Dq-q is very steep during the process when the seismic activity is strong. But very few stronger earthquakes took place in the statistical region when the curve of Dq-q is flat.
1993, 15(1):11-25.
Abstract:In this paper, firstly, we determined the high frequence attenuation tendency(ω-2)of P and S waves of the source in Jingtai area using spectral ratio of two events, utilizing the data of the wired transmission network of Lanzhou; and then measured Qp and Q3 values with the method, of trial and error. It,showed that the Qp and Q3 values (from 1988 to Oct. 1990) of medium on all paths between the mainshock source(Ms=6.2) in Jingtai on Oct. 20 1990 and each station before the mainshock are obviously, higher than those of after the major earthquake and the reference values (Q values of media from, 1984 to 1985). This paper also compared the Q values in Jingtai area with the ones in other places of china. Finally, the reasons of the changes of Q values were discussed physically by using the combination model.
1993, 15(1):26-38.
Abstract:On the basis of the combination model of source, the interaction between conjugate seismogenic structures is calculated and modeled by using the finite element method. It gives the results as follows:
1. The single main shock type. One fault, moves and the other fault does not move, so the single main shock type is formed when the internal angle region of conjugate faults is located in compressive stress region and there exists the adjustment unit of adequate size in the intersection region of conjugate faults.
2. The conjugate single main shock type. Two conjugate faults join together and a great earth quake occurres when the internal angle region of conjugate faults is located in tensile stress region and there is not the adjustment unit or the adjustment unit is little enough.
3. The double main shock type. The double main shock type is usually formed when the inter nal angle region of conjugate faults is located.in tensile stress region and there exists the adjustment unit of adequate size in the intersection region of conjugate faults,the smaller the adjustment unit in the intersection region of conjugate faults is,the shorter the time interval between two major shocks is.
Furthermore, this paper also calculates and discusses the relation between the adjustment unit size and the location of initial fracture region in conjugate faults.
1993, 15(1):39-44.
Abstract:In this paper,we put forward a self-lock model of rock friction, reflecting the relationship of confining pressure and stick-slip. In addition, we discussed the influences of confining pressure and confining stiffness on stick-slip and its stress drop with numerical simulation. The results indicate that:1. The increasing of confining pressure is advantageous to stick-slip. 2. The stress drop of stick-slip increases with the increasing of confining pressure. 3. That the stress drops of natural earthquakes are not as great as that of laboratory experiment is caused by confining,stiffness.
Mao Ke , Zhang Wenmian , Fu Baisheng , Li Zuotang
1993, 15(1):45-51.
Abstract:In this paper, the precursory anomalies of the Jiayuguan earthquake (M=5.4) are expounded. The authors introduce the short imminent prediction to the shock,and the judgement of the post seismic trend. The earthquake has smaller space distribution of precursory anomalies, shorter duration, and general features of space time distribution of precursory anomalies as moderate earthquakes.
1993, 15(1):52-60.
Abstract:According to the gravitational and aeromagnetic interpretation, there exist six larger-scale tectonic belts of EW direction in the crust in the northeastern Qinghai-Tibet Plateau, which have common features as follows:1) they all extend more than 1000 km from east to west and about 60 km from north to south. 2) the deeper it is, the more outstanding the EW directional tectonics is. 3) the central distance between the adjacent tectonic belts is 1°20' and has a equidistant feature. 4) there are also secondary tectonic, belts in EW strike beyond,the large-scale belts. The stong earthquake activities in the northeastern Plateau are closely related to the EW trending tectonic belts. The close relationship results from the left-lateral shear motion of EW structures under acting of the, principal compressive stress in the NE direction.
1993, 15(1):61-66.
Abstract:According to. the definition and,,principle of "fixed mass method", a numerical method is given in this paper, which can be used to judge, the earthquake space-distribution fractal and calculate its dimension. Using this method, the features of earthquake, distribution in North China is studied. The results. Show that satisfying certain statistic conditions, the earthquake distribution belongs fractal in different areas and periods. Selecting different areas and periods in the epicentral areas of the Tangshan and Haicheng earthquakes, the Dq-q spectra are calculated. The,results show that there is no marked change for the Dq versus q curves before and after the strong earthquakes. The results also show that for large areas, the D0 value has reducing trend before strong earthquakes, and increase after the events; it is opposite for small areas; and for some areas, the D0 seldom changes before and after strong events.
Duan Ruwen , Li Lan , Wang Jun , Huang Yahong
1993, 15(1):67-71.
Abstract:This paper presents the experimental results for the strength character of loess in Longxi area, and probes the relationship between strain and stress under deviator stress. The least squares method is used to calculate the strength parameters with a large number of experimental data. The empirical formula between strength parameters and physical characters has been set up by regression analysis for tens of experimental data. This formula can be used directly to the strength estimation of loess and loess slope stability in Longxi area.
1993, 15(1):72-74,88.
Abstract:In this paper, uncertainty of potential seismic source is divided into two types, uncertainty of seismic source type and uncertainty of geometrical parameters of seismic source.The possible plans of potential seismic source area delineation for the studied area are presented by using logic-tree method, the computational steps of seismic hazard analysis. which considers the uncertainty of potential seismic source areas, delineation have been set up. Finally, uncertainty of potential seismic source area delineation in seismic hazard analysis for Shanghai city is discussed.
1993, 15(1):75-82.
Abstract:In this paper, some characteristics of Holocene Series, upper Pleistocene Series and active tectonics in Laizhou Bay segment of Tan-Lu Fault Zone are analysed by use of the shallow seismic surveying profiles. The tectonic action occurred at the end of Pleistocene epoch made upper Pleistocene Series form faults and folds, and a long and narrow arch fold was generated along the east main fault of Tan-Lu Fault Zone. At the two sides of the west main fault, the inferior cross faults (E-W) were developed fully, and they were tension normal faults with high angles.
Li Xihou , Tong Ruizeng , Jin Yaoquan , Su Xiangzhou , Jia Yunhong
1993, 15(1):83-88.
Abstract:This paper introduces the results obtained from investigating and studying paleoearthquakes in Zhangxian segment of the northern fringe fault zone of western Qinling Mountain. The fault zone has been strongly, active since the Later Pleistocene-Holocene and one paleoearthquake occurred in early and mid Holocene respectively in the segment. The occurrence interval of large earthquakes is about 5000 years.
Wu Fuchun , Ji Jianzhong , Lu Xiuling , Xu Junqi
1993, 15(1):89-95,66.
Abstract:Having summarized the earthquake tendency opinions obtained from the National Assemble for Earthquake Tendency Consideration since 1976, we get that earthquakes with magnitude over 5 happened in a quarter of the prediction areas. The prediction accuracy in seismically active regions is greater than that in seismically inactive regions. About 17% earthquakes with magnitude over 5 in the Chinese continent happened in the predicted regions in the same year. The low level predictions is a blind prediction.
Having passed the practical calculation, we think that, the Individual Evaluation Method and the Hedike Evaluation Method are suitable to appraise the prediction accuracy and the binomial distribution test and the Fisher test are the suitable statistical test methods.
1993, 15(1):96-99.
Abstract:刘家峡应力站地理位置为东经103°19',北纬35°48'。其构造位置属于北北西向的河西系庄浪河凹陷带与北西向兴隆山、马衔山隆起带的复合部位的南西缘。该站附近出露的地层为前震旦系马衔山群变质岩系,其厚度约1100m。
1993, 15(1):99-99,102.
Abstract:在自然界中,当含自由氧的水与硫化物或游离硫接触后就可形成硫酸。此硫酸如流至别的地方与岩石和土壤接触,则就会影响土壤和岩石的力学性质。另外硫细菌生活于煤田酸性水中,或生活于硫化物或硫矿床中,它可帮助把硫和硫化物氧化为硫酸。
1993, 15(1):100-102.
Abstract:控制地球运动或形成全球性受力状态的天然力为地球动力,包括地心引力(重力)、地球等速自转力、地球公转变速惯性力和星际引力(增量)4种力。
1993, 15(1):103-108.
Abstract:From material differentiation viewpoint, this paper discusses the crustal evolution in the South China Sea since Late Mesozoic times as well as the geophysical and tectonophysical features of the different types of Crust which exist there. On such basis, a seismic intensity regionalization is given.
Sopyright:China Earthquake Engineering Journal