Abstract:In the light of the coda theory advanced by Aki et al.,this paper deduces a concrete formula for the lasting period ratio τ_H/τ_V of the horizontal and the vertical component of the local earthquake coda. After the approximate treatment, we get:
τ_H/τ_V=I_H/I_V(Q_H/Q_V)^(1)/(4)·B_H/B_V
(1) The formula shows that the changes of τ_H/τ_V mainly reflect the focal body's difference in excitation and attenuation force to the coda wave from different directions in certain range caused by the anisotropy of the medium. The paper also discusses the physical mechanism of the τ_H/τ_V short and imminent anomalies, and rends to think that the occurrences of the anomalies are related to the appearance and closure of the cracks in the medium in earthquake preparatory stage.
The results obtained after processing the Mcnyuan earthquake Ms 6.4 of 1986 and the Haicheng earthquake Ms 7.3 of 1975 show that there appeared the short-period low value anomalies and imminent high value jump in various, degrees.In comparison with the maximum amplitudes, of the direct S wave recorded by Menyuan station before and after the 1986 Menyuan earthquake, it is found that A_mH/A_mV has the similar case with the anomalies of the coda τ_H/τ_V.
Through the analysis to the data of some earthquake cases, the paper finally gives the relation of the magnitude with the anomalous period as
M=0.657lnt+3.44.

Abstract:By using the formula of fuzzy fractal dimenion, the values of fuzzy, fractal dimension of the observational data of precursors in epicentral region and its vicinity before the M 6.1 and M 5.8 Datong earthquakes have been calculated and analysed. The results obtained show that there exist obvious decreases of fuzzy fractal dimension before the earthquakes, and the epicenters were located in the vicinity of the region where the decreases of fuzzy fraetal dimension were most strong. The similar phenomena were obtained in the short-base leveling data before the Tangshan M 7.8 earth quake.

Abstract:Based on the practical research to tackle key problems, which were organized by the SSB, and according to the prediction experiences that are accumulated over a long-period, the short-temporary anomalies are discussed this paper. There are six indices used:the shock event lack curve, the wave velocity ratio variation, the b value time sweeping, the accumulated no-seismic unit numbers, the parameters of coda and the time fractal dimension of seismic frequency hierarchy.
The simple conclusions are:
(1) The anomalies for the most indices appear about 3 months before main shock.
(2) It is not interrelated between the size of anomaly and the magnitude of the coming strong earthquake.
(3) For the most indices the Xu's mark is about 0.5-0.6 in the prediction check.

Abstract:The digital seismograph network set, up by China and France in Zhangye had operated in 1988. There are eleven substations. which were situated in middle segment of Hexi corridor and Qilian Mountain. Using the small earthquakes recorded by Zhangye digital network the Parameters of earthquake of Minle. Su'nan. Zhangye and Linze area were measured. The stress drops of these four areas are a range from 6.1 to 9.5 bar using P wave. and from 26 to 60 bar using S wave, which belong to lower drops The change curve of stress drop versus time had Showed lower value about in a month before Su'nan earthquake (M_s=5.7). This phenomenon may be a precursor information. In this paper the different results of stress drops measured using P wave and S wave were preliminarily discussed.

Abstract:This paper discusses the characteristics and mechanism of anomalies of CO₂ concentrations in 0.5m and 2.0m depth of the ground fissure in Xi'an. The results indicate the anomalous ranges of CO₂ concentrations in 0.5m depth are wide and approximately equal to the ranges damaged by the ground fissures. CO₂ from 0.5m depth is mainly originated from biogenic agency. But the anomalous ranges of CO₂ concentrations in 2.0m depth are narrow and closely relative to the loca-tion of the main ground fissures. CO₂ from 2.0m depth is mainly originated from rupture, of carbonate rock caused by fault movement.

Abstract:By using the pattern recognition method, this paper divides the potential earthquake source zones of M 5.0 and M 5.5 in Zhejiang Province and its vicinity, and studies the features of the Statutory background comparing with the earthquakes of strong earthquake area. It shows that there exists difference of their background of geological structure and deep structure, for the two zones. Finally. it points out the potential source area occurring M 5.0 earthquake in the future.

Abstract:Based on the former researches, the overall characteristics, architectonic setting, and dynamic properties of intraplate seismicity in Chinese continent have been analysed in this paper. Taking the Chinese continent as a whole system, this paper researched the multiple stratification of earthquakes and the relationship between different size of earthquake, approached possibility of self-organizing earthquake preparation model of intraplate seismicity in Chinese continent.

Abstract:This paper studied a high precise method separating artificial potential difference Δv from the potential difference E which is synthesized With the geoelectric potential difference (Vsp) and Δv on a basis of regressive analysis, harmonic analysis and prediction theory. Lots of the calculation result show:If the changes in Vsp are more regular, the calculation precision through the method is obviously higher than that through the conventional methods; If the changes in Vsp are less regular, the precision through the method is higher than (or close to) that through the conventional methods.

Abstract:This paper studies the change features of onset sign of seismic wave, amplitude ratio, duration time ratio of coda, and attenuation coefficient of coda before and after the Kuerle M_s 5.2 earthquake on May 26. 1988, the Keping M_s6.5 earthquake on Feb. 25, 1991. It is found that before the two earthquakes the parameters above-mentioned are of anomalies in various degrees. Before the earthquakes, the stronger the coincidence of P wave onset is, the longer the duration time is. the larger the magnitude of coming earthquake is; the sudden jump of amplitude ratio is the obvious sign of earthquake that will occur soon; the station in whith the anomaly of attenuation coefficient of coda first appears is close to the epicenter of coming earthquake. Based on the anomaly features of the parameters, we have successfully predicted the Hejing M_s5.2 earthquake on June 6,1991.

Abstract:For two types of earthquake focus model ("locked fault" and "expanding ball" models), the distributions of stress and. strain were calculated separately for different combinations of large scale layer medium, then the resistivity anomalies caused by additional stress and strain were calculated in order to reveal the affect of large scale medium condition on the observation of geoelectrical station. The results show that the change of combination of lrage scale layer medium has great affect on resistivity anomaly, and the good conditions are:(1) potential for earthquake should happen in hard rock layer; (2) the thiner of such hard rock layer, the better; (3) the depth of soft covering layer should not be too thick. Besides, the results show that the local medium combination and its mechanic and clectrical characteristics also have great affect on resistivity anomaly.

Abstract:Based on the probability statistics, regression analysis and grey assoeiation analysis, the paper analysed and studied the Seismic data in the seismicity areas in China and the global, and the Elnio phenomena. The results show that there is no obvious correlative relation between earthquakes and Elnio over a large range, but there is a good correlative relation between earthquakes and Elnio in a limited area. For example, Elnio always occurs in a high seismicity years in the areas as the eastern Pacific upward district and Philippines. There also exists a good correspondent relation in Taiwan and Qing-Zang Plateau regions in China.

Abstract:1989年4月16日04时34分在四川省甘孜藏族自治州巴塘县境内发生M_s6.7地震,随后于4月25日10时13分、5月3日13时53分和23时41分分别发生M_s6.7、M_s6.4和M_s6.2地震,到9月30日止,共发生M_L ≥ 1.0地震21000余次,M_L ≥ 2.0地震3428次,其中M_L 2.0-2.9地震3121次,M_L3.0-3.9地震273次,M_L4.0-4.9地震25次,M_L5.0-5.9地震5次,M_L6.0-6.9地震4次。

Abstract:峰峰地震台位于河北省邯郸市峰峰矿区,处于晋、冀、鲁、豫四省交界的重点监视区内。1984年3月国家地震局地壳应力研究所在该台安装了TJ-1型体应变仪。

Abstract:天祝、景泰6.2级地震后,共发生M_s ≥ 1地震186次。从图1可以看出,震级随时间的衰减是明显的。

Abstract:众所周知,新疆地处欧亚板块腹地,是我国主要的内陆地震活动区。一般认为其强震的活动主要受印度洋板块向北东推挤作用的影响。

Abstract:测距网图形是由中点多边形和大地四边形组成的。现行《大地形变测量规范补充规定》中给出的计算测边网图形闭合差及其限差的公式为。

Abstract:兰州地磁台是国家基本台和国际资料交换台站之一。该台现有绝对观测仪器8台,相对观测仪器2套,通常用Askania(570422)仪测量磁偏角(D),用Askania(THM.570707)仪测水平强度(H),用CHD-6型核旋仪测量垂直分量(Z);相对观测仪器为57型,备用仪器为CB₃型号。

Abstract:The synergetic effect of abnormal behavior of animals before earthquakes is discussed in this paper. The result of a simple model based on the interaction between animals can explain the statistical data. It was also pointed out that the system of animal colony reacts to the stimuli of environment in a nonlinear way, which leads to more complexity in the application of this phenomena in earthquake prediction