Wang Zhouyuan , Yao Zhengsheng , Du Zhijun
1991, 13(1):1-8.
Abstract:Based on[1] [2], imaging of seismic velocity structure of crust and upper mantle for the northern portion of N-S Seismic Belt is made. The velocity distribution of upper crust exists three low-velocity belts oriented near EW trend, which agrees with recent active fracturing zones, while in upper mante there are a lot of low velocity belts trend NE and NW, which appear network structures across each other. It is pointed out that the Haiyuan-Guyuan fracturing zone may be a great deep fault, being low velocity belts in upper-, lower-crust and upper mantle. Finally, it is suggested that the northeastern boundary of the Qinghai-Xizhang Block may locate along Tianzhu-Lanzhou-Jingning-Qianyang-Lueyang-Jiangyou, by using inversion.
Zhang Wenmian , Tian Shaobai , Wu Jianhua
1991, 13(1):9-16.
Abstract:In this paper, sudden anomalies of impending earthquake and obvious trend anomalies are analyzed statistically for eleven earthquakes(M ≥ 7.0) from 1969 to 1900 in China. The whole characteristics of sudden anomalies before the megaseisms, the distributing rules of the item-and-frequency with time(the interval from the sudden change date to the earthquake occurrence date), the synthetic distinguishing method of imminent anomalies etc. are discussed. The synthetie indices of imminent prediction for great earthquakes and the effectiveness of time prediction are further discussed.
1991, 13(1):17-23.
Abstract:In this paper, on the basis of K.Aki's theory of coda, with the data of three component seismic records from the seismic network, Qc value for the upper crust medium, α value for the amplitude attenuation coefficient and m value for the attenuation exponent of the coda predominant frequency versus time after origin are continuously estimated, and their errors are also appraised, around three moderate earthquakes of Lingwu-Wuzhong region in Ningxia. As a result, Qc value increases about 30% of the normal value, α and m value decrease or first decrease and then increase in aforesaid region. before the moderate earthquakes. It shows that it is possible to gain some precursor informations of strong earthquakes from the feature changes of coda physical quantity with the regional seismic record if the available data are properly and timely processed.
1991, 13(1):24-29.
Abstract:On the basis of observation data, geochemical characteristics of gases along the active fault zones in the southern Zhangjiakou area (including the northwestern Beijing) are studied. The relationship between releasing gases in the hot spring form of the active fault zones and regional geology, hydrogeological condition is discussed. The optimal selection of observation point and observation components for earthquake prediction is also suggested.
1991, 13(1):30-34.
Abstract:In this paper, the temporal-spatial variation characteristics of wave velocity ratios of small earthquakes before the Heze earthquake with Ms 5.9 are studied. It is found that there is a concentrative area of low value anomaly of wave velocity ratios near Heze for two years. When the wave velocity ratio rises again up to the maximum value in the concentrative area, the activity of small earthquakes becomes quiet. Then the low values of wave velocity ratios extend toward outer. When the wave velocity ratios of small earthquakes in the periphery change to the minimum value, and then the values rise again to normal, the mainshock occurred in the concentrative area of low values. Before the mainshock, the low values of wave velocity ratios last three years, restoring to the normal values until about 15 days prior to the mainshock. Finally, some relative problems about the wave velocity ratio anomaly are discussed.
Shi Shaoxian , Fu Hong , Shen Bin , You Chuanxia
1991, 13(1):35-40.
Abstract:In this paper, the scientific thinking, method and reason of the medium-and short-term earthquake prediction and the forecast on the spot before and after the Lancang earthquake with M=7.6 and the Gengma earthquake with M=7.2, which occurred on Nov. 6, 1988, have been objectively expounded. The main reason of the medium-term prediction includes the basic seismieity characteristics, the 47-year recurrence period of great earthquake and the accumulated strain energy. The main criteria of the short-term prediction embrace the dynamic deduction of seismicity centers in the southwestern Yunnan, the direction shifting track of epicenters of earthquakes with M ≥ 5.0 and the analysis of seismicity process. Σ√E-lgt and b-value intercept method is effective methods determining and predicting the largest aftershock on the spot, Finally, this paper sums up and reconsiders the prediction.
Wang Changling , Liu Yaowei , Tao Shufen
1991, 13(1):41-49.
Abstract:In this paper, we have computed the data of hourly values and daily values of radon content by means of the optimal spectrum-an alysis method of tidal wave. The results show that there exist semidiurnal and daily wave components in hourly value sequence of radon content measured at Wuquanshan spring of Lanzhou, which are consistent with the theoretical earth tide; there exist semimonthly and monthly wave components in daily value sequences of radon content measured at Liaocheng drill of Shandong Province, Zhangdaokou drill of Tianjin City, Pingliang spring of Gansu Province, which are consistent with the theoretical earth tide. It has proved that drills and springs having good environmental conditions and the data having good quality, the change of radon content can reflect the change of tidal stress of earth crust.
1991, 13(1):50-56.
Abstract:This paper uses the complex relative analysis method to extract anomalous information in earth tide of well-water level before earthquakes and offers the numerical standard distinguishing the anomalies quantitatively. The daily atmospheric pressure coefficient replaces the mean atmospheric pressure coefficient so as to correct the effect of atmospheric pressure on well-water level. It is suggested that anomalous rate of data and reflective ratio of anomaly to earthquake can be taken as standard distinguishing observed quality of water-level data. Finally, a practical example using this method is cited.
1991, 13(1):57-62.
Abstract:The Lancang-Gengma earthquake sequence of 1988 formed a obvious epicenter zone which is in NNW strike. The events of M7.6 and M7.2 formed it's seismic deformation belt in the ground separately. The earthquake-generating tectonics of M7.2 earthquake is Hanmuba fault in NNW trend. The M7.6 earthquake showed the complicated character of earthquake-generating tectonics, it formed obvious seismic deformation belt separately along Muga fault and Laneang-Menghai fault. The activity of strong aftershoek related to the faults in NE trend in Laneang-Gengma area. Therefore, Laneang-Gengma earthquake sequence has complicated patterns of earthquake-generating tectonics and seismic rupture.
1991, 13(1):63-70.
Abstract:In this paper,we study the earthquake sequence types using the grey relational analysis in grey system theory.The stress drop (△δ),seismic moment (M0),rupture speed (V),length (L) and width (D) of the aftershock region,magnitude difference between the main shock and the largest aftershock (△M) and a-value,b-value as well as P-value in aftershock sequence are considered as grey relational factors,at the same time the earthquake studied is considered as reference sequence of number (X0) and some historical earthquakes are considered as comparative sequence of number (Xi),when we carry out grey relational analysis.In addition,a great earthquake once occurred in some region,how to determine the earthquake sequence type rapidly using the grey relational analysis is also studied.The results show that this method is a good useful method and it is of certain practical value to us.
1991, 13(1):71-77.
Abstract:Using the methods of periodogram and autoregressive model in a stationary random process, we discuss the rules and give the possible time interval in which several moderately strong earthquakes will happen in coming one hundred years in Fenwei seismic belt.
Wang Hualin , Chen Jintai , Geng Jie , Wang Lijun
1991, 13(1):78-84.
Abstract:The fault activity in and near Shengli Oil Field is studied in the light of steps and methods that are suitable for studying fault activity in plain area. The results show that Wuli-Yidu fault, Guangyao-Qihe fault and Chengzikou fault are active faults during the Quaternary. And we also discuss the active features of Wuli-Yidu fault and the marks of Quaternary active faults in and near Shengli Oil Field and so on.
1991, 13(1):85-90.
Abstract:The following article is based upon the account in Fan Ye's Book of Later Han Dynasty:Biography of Zhang Heng.It clearly puts forward the restoration plan for various functions and principles of the Houfeng seismograph by Zhang Heng.The plan stresses that the Houfeng seismograph can receive the vertical component and the horizontal component of the first seismic wave,and thus can be used to tell the approximate direction of the seismic source.When the first seismic wave is not strong enough for an alarm to be given,it is used to surpress the secondary wave to prevent such secondary wave as the shear wave from interfering the determination of the azimuth.The paper deduces that Zhang Heng had spent several decades for observing,experiment and improvement during the course of inventing this device.
1991, 13(1):93-96.
Abstract:阿尔金断裂带中段从阿卡吐到野马泉保存有一条比较清楚的地震形变带。1987年作者对该形变带进行了详细调查。本文主要根据现场考察资料,描述了地震形变带的基本特征,进而确定了该次地震事件的参数,並讨论了地震成因。
1991, 13(1):97-98.
Abstract:地震周期规律可用于预测未来地震形势的发展趋势。本文选取了我国古代产生的延用至今的甲子纪年的地支数12年作为周期数,对我国有记载以来的8级以上地震(表1)活动时间作了相关统计研究,发现它们与12年周期相关性较好。另外,对我国本世纪发生的7级以。
1991, 13(1):99-104,98.
Abstract:
Sopyright:China Earthquake Engineering Journal