Table of Content

10 June 1998, Volume 20 Issue 2

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Brief Report

THE ANOMALIES OF SUBSURFACE FLUIDS BEFORE THE ZHANGBEISHANGYI EARTHQUAKE AND TRACE PREDICTION OF THE EARTHQUAKE

Che Yongtai, Wang Jihua, Lin Yuanwu, Zhu Qingzhong, Zhang Peiren

1998, 20(2):  99-104. 

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Before the Zhangbei Shangyi M 6.2 earthquake,the anomalies of high value of subsurface fluids have appeared for more than two years in the north area of Noth China.Some anomalies of subsurfase fluids rose one after another and coordinated with some moderate and moderate strong earthquakes in 1997,and some typical short impending earthquake anomalies appeared 2 months earlier than the earthquake in the region of 100～200km away from the epicenter.These anomalies were traced for two years,with the improving of the understanding on earthquake risk,the short impending earthquake prediction was made successfully half month before the earthquake.

INTERMEDIATESHORT TERM ANOMALY OF UNDERGROUND FLUID IN TAIPINGZHUANG WELL BEFORE THE ZHANGBEISHANGYI EARTHQUAKE

Zhang Peiren, Liu Chenglong, Wang Zhimin, Tao Jingling

1998, 20(2):  105-109. 

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his paper present the anomalies of underground fluid in the Taipingzhuang well of Beijing suburbs which appeared several times before the Zhangbei Shangyi M 6.2 earthquake.Though these anomalies seem to be related to Zhangjiakou M 4.2 earthquake of May 25,1997 and Wulatehouqi M 5.0 earthquake on October 21,1997,we consider that the anomalies and the earthquakes should be regarded as the respond to crust activity in the north area of North China and increase of stress in the regional stress field.So it can be identified as the intermediate short term precursor of Zhangbei Shangyi M_s 6.2 earthquake January 10,1998.

PHYSICAL ANOMALIES OF GROUNDWATER AND SHORT TERM AND IMPENDING PREDICTION BEFORE THE ZHANGBEISHANGYI EARTHQUAKE

Zhu Qingzhong, Gu Yuanzhu, Liu Chenlong 

1998, 20(2):  110-112. 

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Before the Zhangbei Shangyi earthquake,obvious middle and short term and impending anomalies of water level and water temperature appeared in the Tayuan and Taipingzhuang well.Based on these anomalies in cambination with other precursars,we have proposed short term and impending prediction to a certain extent.

MONITORING OF CO₂ IN FAULT GAS AT HUAILAI AND SHORTTERM PREDICTION OF ZHANGBEI SHANGYI EARTHQUAKE

Wang Jihua, Lin Yuanwu, Gao Shongsheng

1998, 20(2):  113-116. 

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A simple summary is made on anomaly examples of CO₂ in fault gas before moderate strong earthquakes,which had been observed in Houhaoyao monitor site in Huailai county,Hebei province since 1991.The characteristics of change in CO₂ of fault gas before and after the Zhangbei Shangyi earthquake (10 January,1998) and short term prediction of the earthquake is presented.And prediction of three essential elements of the earthquake by using one monitoring site of CO₂ in fault gas and some relevant problems are discussed preliminarily.

OBSERVATION OF CO₂ IN THE FIELD OF ZHANGBEI SHANGYI EARTHQUAKE AND PREDICTION OF SEISMIC TREND AFTER MAIN SHOCK

Lin Yuanwu, Liu Wuzhou, Wang Jihua, Che Yongtai

1998, 20(2):  117-121. 

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Dynamic characteristics of CO₂ at 4 observation sites in the field of Zhangbei Shangyi M 6.2 earthquake are studied by using fast measurement method for CO₂.The source of CO₂ is discussed preliminarily.The results indicate that no anomaly in CO₂ is observed.It is suggested that there is no signal of increase in tectonic stress after Zhangbei Shangyi earthquake.According to the regulation of change in CO₂,on Jun.10 and Feb.3,1998 ,respectively,we predicted that there will be little possibility to occur strong aftershocks of M_s≥5.0 in 15 days.The fact indicates that the prediction is correct.It is suggested that the fast measurement method for CO₂ will pay an important role in prediction of seismic trend after main shock.

THE PREDICTION AND RESTUDY TO THE ZHANGBEI SHANGYI EARTHQUAKE BY USING SEISMICITY ANALYSIS

Dong Ruishu, Ren Guoqiang, Ran Hongliu

1998, 20(2):  122-130. 

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This paper is to summarize and restudy the mid long term prediction of Zhangbei Shangyi earthquake throuth seismic activity analysis.First,Yanshan Bohai seismic belt was divided into four sections by the analysis of seismic activity and Zhangjiakou section was predicted to be the risk zone where strong shocks may occur in the futrue.Second,No.28 potential zone was predicted to be the risk zone in 1～3 years.This area is near the epicenter of the Zhangbei Shangyi earthquake.Third,restudy of the prediction indicates that strong earthquake structrue background should be taken seriously and regional seismic activity is important too.

APPLICATION OF PRECURSORARY GEOLOGY TO PREDICTION FOR THE ZHANGBEISHANGYI EARTHQUAKE AND ITS IMPLICATIONS

Xu Haomin

1998, 20(2):  131-134. 

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In October 1996 the prediction was made that the region along Yanqin,Zhangjiakou,Shangdu and Jining northwest to Beijing is also the area of stress concentration and should be given attention.The Zhangbei Shangyi earthquake of January 1998 occurred just at the central area confined by Zhangjiakou,Shangdu and Jining.Therefore this long term estimation for the seismic risk area should be considered to be successful.Combination of macroscope and microscope should be beneficial and effective for earthquake prediction.

SEISMOTECTONICS AND MACRODAMAGE FEATURES OF THE ZHANGBEI SHANGYI EARTHQUAKE

Xu Xiwei, Ran Yongkang, Zhou Bengang, Yin Gonming, Li Jianhua, Liu Wuzhou

1998, 20(2):  135-145. 

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The regional seismotectonic environment of the Zhangbei Shangyi earthquake is stated in detail together with its seismic intensity distribution,co seismic ground fissures,focal mechanism solutions and interpretation of linear structures on the MSS satellite images around the epicenter.Its possible seismogenic fault or structure is also discussed.It is suggested that this earthquake was resulted from the most recent abrupt slip on a NNE trending fault at the northwestern termination of the Zhangjiakou Penglai fault zone.The future seismicity of the Zhangjiakou Penglai fault zone is worth to pay attention.

PRELIMINARY STUDY ON THE SEISMOTECTONIC CHARACTERS OF THE ZHANGJIAKOUPENGLAI FAULT ZONE

Xu Jie, Song Changqing, Chu Quanzhi

1998, 20(2):  146-154. 

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The Zhangjiakou penglai Northwest trending fault zone is an important seismotectonic zone in North China.We have done a preliminary study about its seismotectonic characters on the basis of the geological,geophsical and seismic activity data.The fault zone,which consists of nearly 20 NW-NWW trending faults,is a crust structure one which has an important controlling effect on the regional teconics of the Cenozoic Era.The fault zone is left lateral slip on the whole.In the Palaeogene period the zone's middle part was very active,after that its northwest and southeast sections became active in the Neogene period.The fault zone merges with several NE trending active teconic zone,so it owns a kind of tectonic combination that NW and NE trending faults intersect each other and includes 5 complex tectonic merging parts.The major earthquakes of M≥6 and most of middle small earthquakes assemble these parts.Both NW and NE trending fualts can cause earthquakes.So it demonstrates the character of conjugate ruptures.But the NE trending fault can produce bigger earthquakes than those of NW trending fault.The Zhangbei Shangyi 6.2 earthquake can be the result of northwestward extending along this fault zone.

THE STRUCTURE OF THE CRUST AND UPPER MANTLE FOR THE ZHANGBEI-SHANGYI SEISMIC AREA AND ITS NEIGHBOURING REGION

Zhao Guoze, Liu Guodong, Zhan Yan, Jiang Zhao, Liu Tiesheng, Tang Ji, Wang Jijun, Li Wenjun, Liang Jingge

1998, 20(2):  155-163. 

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It is shown that the structure of the crust and upper mantle (thickness,geothermal field etc.) beneath the Zhangbei Shangyi earthquake area,which belongs to Inner Mongolia geo axes,has the nature of a transition zone as compared to its surrounding regions,Yanshan mountain fold belt,rifting basin of North China,rift system of Shanxi province and Erdos block.The Zhangbei Shangyi earthquake area is located near the Zhangjiakou Bohai Sea Penglai tectonic belt (ZPB) which is a significant tectonic boundary.Along the ZPB a relative low resistivity zone appears in the whole lithosphere.The width of ZPB is about 40km and becomes bigger with increasing depth.The structure of seismic velocity similar to electricity also occurrs along the ZPB.A NNW trending tectonic belt in the crust is newly detected beneath Zhangbei Shangyi earthquake area.The NNW trending tectonic belt and ZPB are postulated to play an important role in a combining way for pregnancy and genesis of the earthquake.The recent results of magnetotelluric observation indicate that there is a low resistivity layer at the depth of about 15km beneath earthquake area,which is deeper and thinner than that to the south of Shangyi Chongli fault,which is tectonic boundary between Inner Mongolia geo axes and other southern tectonic units.The foci of main shock and most aftershocks are located above the low resistivity layer in the crust.

VARIATION AND ANALYSIS OF RESISTIVITY BEFORE AND AFTER THE ZHANGBEI-SHANGYI EARTHQUAKE

Tang Ji, Zhao Guoze, Wang Jijun, Li Wenjun, Zhan Yan

1998, 20(2):  164-171. 

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MT data were acquired at two sites after Zhangbei Shangyi M6.2 earthquake on January 10,1998.At 511 site ,which is 26km in distance to southeast from the epicenter,the data were obtained in January 13 and 21 of 1998,where the MT measurement was done in June 1 of 1994.At site MMC MT measurement was made continuously from January 16 to 20 of 1998.The results indicate that : (1) Resistivity for TE polarization decreased within period range 0.24 sec.and resistivities for M polarization increased generally in comparison with data of June 1,1994.(2) The resistivity for both polarizations at site MMC increased gradually from day to day.The minimum appeared on January 16 and the maximum appeared on January 20.(3) The change of resistivity possibly reflected the resistivity resumption process after main shock.In addition,electric structure of subsurface corresponding to the MT data are analysed.Activity of the fluid in the crust is possibly related to the change of resistivity.

A COMPARATIVE STUDY ON THE SEISMICITIES OF THE ZHANGBEI-SHANGYI EARTHQAKE AND THE DATONG-YANGGAO EARTHQUAKE

Deng Zhihui, Chu Quanzhi, Li Jianhua, Liu Peixun, Liang Xiaohua

1998, 20(2):  172-178. 

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There are many differences of seismicities between the Zhangbei Shangyi earthquake and Datong Yanggao earthquake,although the distance is less than 150km between the epicenters of them.The conjugate directions of EW and NS are the dominant directions of the regional earthquake (M_s≥5.0) epicenter arrangement,active faults with seismic frequence anomalies,the tendency of earthquake occurence near epicenter,the long axis of seismic gap,before Zhangbei Shangyi earthquake,and distribution of aftershock epicenters.While conjugate directions of NE and NW are the dominant directions of various seismic anomalies for Datong Yanggao shock.The causes of such a direction difference may be associated with the tectonic setting and the additional stress field.

GROUND FAILURES CAUSED BY THE ZHANGBEI-SHANGYI EARTHQUAKE IN SOME TYPICAL SECTIONS

Che Yongtai, Liu Wuzhou, Wang Jihua, Lin Yuanwu

1998, 20(2):  179-182. 

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Same parts of ground were destroyed by Zhangbei Shangyi M6.2 earthquake.The main styles include ground fissure,falling of river bank,rolling and falling of large stones,sandboils and waterspouts and ice surface parting.In this paper,the phenomena of ground failures in some typical sections are simply presented and the scientific significances are analysed.

POSTEVENT INVESTIGATION AND ANALYSIS OF MACROSCOPIC ANOMALIES RELATED TO THE ZHANGBEISHANGYI EARTHQUAKE

Liu Wuzhou, Che Yongtai, Lin Yuanwu, Wang Jihua

1998, 20(2):  183-188. 

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ased on the results of field investigation on macroscopic anomalies of the Zhangbei shangyi earthquake,we analyze the total number and main apparent form of different kinds of macroscopic anomalies,as well as time space distribution features of macroscopic anomalies.Then the cause and implication to earthquake prediction of macroscopic anomalies are discussed.