1998, 20(4):1-11.
Abstract:Just for 3-D/2-D geological structures,the decomposition technique of MT impedance tensor is developed.It can separate and remove the twist distortion of MT corresponse function shape resulting from 3-D local abnormal objects near surveying site by using the technique to analyze the MT data of each independent site.The theoretical model tests in this paper have shown the effectiveness of the technique in removing the local distortion.
1998, 20(4):12-17.
Abstract:In this paper,the results of detailed interpretation on primary waves in the Eryuan-Jiangchuan deep seismic sounding profile in Yangtze paraplatform region of Yunnan Province are presented.Here the improved ray-trace method is used.The results show that in the middle part of the profile there is very thick sedimental cover.The basement interface here is depressed and its depth is more than 10 km.The Meso-Cenozoic sediment thickness is also greater than other places.This depressed region is corresponding to southern part of ancient Panxi rift valley.In this place the seismicity and magmatic intrusion are relatively weaker than other two ends of profile.In its western part the basement relief is quite changeable and a small basin formed in the Erhai lake region.In the basement layer there exist raised places with higher velocity and there are corresponding violent frequent seismicity and basic magmatic intrusion.The similar situation also takes place in eastern part of the profile.It means that in the basement layer there exist some corresponding relations between seismicity,magmatic activities and distribution of high velocity matters.These high velocity matters are estimated to be some basic or ultrabasic magmatic materials.They are the products of semimelting magmatic matter upwelling from deep upper mantle. Their activities trigger occurrences of a lot of earthquakes in the region.
Lan Congxin , Guo Daqing , Shi Telin , Yang Liming
1998, 20(4):18-26,34.
Abstract:The theory of self-organized critical phenomenon is used to do a deepgoing research in earthquake prediction.Based on the physical meaning of all the variables,their usability in seismic science is discussed.The critical point problem about increasing small or moderate events before a strong earthquake is studied.Both the critical probability and the threshold of the correlation length are quantified.The spatial evolution pattern is essentially a kind of quantitative seismicity distribution map and can give approximate prediction for the spatial position of a future earthquake.
Yuan Daoyang , Liu Baichi , Lu Taiyi , He Wengui , Liu Xiaofeng , Gan Weijun
1998, 20(4):27-34.
Abstract:In this paper,according to the 1:50 000 geological mapping information in east segment of the northern Qilianshan active fault zone,authors systematically analysed the geometry,inhomo-geneity features of the displacement distribution,slip rates,palaeoearthquakes and historical earthquakes in time and space along the fault zone,then summarized the rupture segmentation,It is considered that the east segment of the active fault zone can be devided into Laohushan and Maomaoshan-Jinqianghe first class rupture segments.The Laohushan fault can be devided into east and west segments,the Maomaoshan-Jinqianghe fault can devided into the Maomaoshan and Jinqianghe second class segments.
1998, 20(4):35-42.
Abstract:Seismic precursor is very complicated.Its temporal and spatial distribution is quite unequal, but in some places and during certain periods it may appear obviously.It is possible to predict earthquake successfully if we have corresponding ability of monitoring and analysing earthquake. Based on the fact of successful impending earthquake prediction in Jiashi and several others in China.authors have analysed the possibility and limitation of impending earthquake prediction in the paper.Finally.It is pointed out that because earthquake prediction is not successful generally, the predictions were made mainly by experience.In this situation,it might be better to take tactics of solving easy problem firstly and hard problem secondly,and to concentrate ascendant strength on the important monitored regions where seismic precursors would appear frequently.
Zhang Fanmin , Li Qinghe , Zhang Yuansheng , Shen Guoying , Fan Bing
1998, 20(4):43-49.
Abstract:According to the theory of artificial neural networks,a preliminary study has been performed to test the ability of recognising seismic signals and phases by using artificial neural networks,and the phase recognition has been achieved for three-component recordings by using vector modulus of these seismic records as the network input.Results show that the method is very valid in the determination of seismic phases and arrivals,especially for high signalnoise ratio records.
1998, 20(4):50-56.
Abstract:In order to study the fundamental pattern and feature of moderately strong earthquakes in the north of Sichuan Province and its vicinity,the division of seismicity periods and feature of earthquake migration of north-east seismic belt in the studied region were analyzed.It is pointed out that seismicity were mainly attributed to north-east seismic belt in the studied region.It is consid-ered that there will be possibility of the occurrence of M≥6 earthquakes in the regions of Maowen-Beichuan-Wenchuan,Dayi-Tianquan-Baoxing and Lixian-Tianshui-Wushan in the coming years.
Wang Zhouyuan , He Shaolin , Peng Weirong , Ji Fengying
1998, 20(4):57-62.
Abstract:Analysed the features of earthquake interval pattern in some regions and their relation to seismic trends.Before the 1960s,the whole world had gone through a seismicity period,the earthquake intervals kept stable and uniform distribution basically,then,weakened and changed to quiety.The chief characteristics are higher values,increased situation remarkably,scattered pattern and existence in groups outstandingly.The higher values of intervals for global and larger regions have inermission vantage of near 20 years.A seismicity may be taken as a ‘window’ of seismic situation of higher grade seismieity.Finally,the seismic trends in the future years are discussed.
1998, 20(4):63-69.
Abstract:The relationship of inferring the state of additional strain by additional principal stress ratio was derived from physical formula of elastodynamics and the relation between additional stress field and fault activities was analyzed.Based on the calculation results of additional principal stress ratio for the ground stress stations in Gansu Province from 1983 to 1995,the correlation of additional principal stress ratio with moderate earthquakes was studied,the seismogenic mechanisms were further discussed and some preliminary results were got.
Wang Yongzhong , Li Rongfeng , Ye Zhenmi
1998, 20(4):70-74.
Abstract:Based on the seismically hydrogeochemical survey,a new MIS system named seismic hydrogeochemistry database management system(SHCDMS) has been developed successfully.The system was written in FoxPro2.5 environment under UCDOS(Chinese DOS operation).The system can manage daily data of hydrogeochemistry observation station and give out all kinds of reports and charts needed.The system has a good user interface and sufficient function.Through two years running,it is shown that the system fits in with the need of analysis forecast center and observation station.
Cai Shuhua , Wang Lanmin , Yuan Zhongxia
1998, 20(4):75-82.
Abstract:A method of determing the maximum epicentral distance of seismic landslide and the maximum fault distance of seismic landslide is proposed through analysis on data of seismic landslide disasters in Shaanxi-Gansu-Ningxia-Shanxi loess region.Some nonlinear fitting calculations were carried out and a preliminary mathematical relationship between the magnitude 5.5≤MS≤8.0 of earthquakes and both the maximum distances is developed.Furthermore,the main factors of affecting the seismic landslide disasters are discussed in order to study accurately this relationship for different areas.
Tu Delong , Wang Zanjun , Zeng Baohong , Gao Qiang
1998, 20(4):83-90.
Abstract:On the basis of airphoto interpretation,seismogeology survey and palaeoearthquake and historical earthquake study,the activity patterns of the Holocene faults in Huangshui basin are shown and the trend of seismic avtivities is predicted.It is found that the eastern part of the basin is an active structure block.
1998, 20(4):91-93.
Abstract:Radon in groundwater of the Dongxia spring was put into observation in 1987,and its data were continuous and reliable.Based on the judgement of data anomaly by using nonlinear regression and hydrochemically practical processing method,the anomaly that exceeds the annual dynamic value by two times residual standard deviation can be regarded as seismic anomaly.The radon data have shown obvious anomaly reflection before the earthquakes around the boservation station.
1998, 20(4):94-99.
Abstract:1997年第4期《西北地震学报》发表题为《毕奥理论中3个基本参数显式解》一文,文中在概念和公式推导中都有不妥与错误之处.在此提出看法,疑义相与析.
Sopyright:China Earthquake Engineering Journal