Table of Content

02 September 1987, Volume 9 Issue 3

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Brief Report

THE VERTICAL DEFORMATION BEFORE AND AFTER THE TANGSHAN EARTHQUAKE OF 1976

Xie Jue-min, Huang Li-ren

1987, 9(3):  1-19. 

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Based on the data of 18 times of leveling carried out during 1954 to 1985, the relative stability degrees of relevelling nodes in the Tangshan area are calculated. According to these results, the characteristics of crustal vertical deformation before and after the Tangshan Earthquake(28/7/1976,M_s=7.8) are studied. Our study indicates that probably since 1968 significant relative movements between structural blocks in that area had appeared and continued till 1978. The seismic fault was in locked state before the quake. Finally, some viewpoints about the deformation monitoring and the evaluation of risk region of a strong earthquake are also presented in this paper.

NEW BOOKS——GRAPHIC METHOD FOR PROTOLITH METAMORPHIC ROCKS

Wang Yuan

1987, 9(3):  19-19. 

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THE AGE OF ACTIVE LONGMENYI FUALT JUANCHUAN COUNTY, YUNNAN PROVINCE

1987, 9(3):  20-20. 

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THE RECENT CHARACTERISTICS OF ACTIVE MAIN FAULTS IN THE BEIJING-TIANJIN-TANGSHAN REGION

Xiang Jia-cui, Zhang Cun-de, Wan Su-fan, Zhang Chong-li, Li Tie-ming, Quan Xin-hua

1987, 9(3):  21-28. 

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In this paper, we have studied the recent activity of main faults in these regions using geodetic data obtained from short leveling, regional leveling and short baseline measutements across faults, vertical movement values for about twenty faults have been calcalated and horizontal movement values for some faults have been also obtained from repeated leveling and baseline measurements. According to the level of fault activity, the faults may be divided into two classes, the annual vertical movement rate is 1 to 10mm for the first class, 1-0.1mm year for the second one.The recent active characteristics of these faults are discussed in combination with geological and geophysical data. There appear to be two aspects, some intensively active faults in Quaternary period have remained to be intensively active in recent years; the rate of fault activity is of no linear relation to time in these regions, suggesting an ac-celarated motion along 9 faults in an area with radius of 200km from the epicenter before Tangshan earthquake.

A MATHEMATICAL SIMULATION OF STRUCTURAL FEATURES IN FEN-WEI FAULT BASIN ZONE

Liang Hai-hua

1987, 9(3):  29-37. 

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The geological and geophysical features in Fen-Wei fault zone are simulated by finite element method. The results of computations indicate that these features are not likely to be caused only by horizontal force; the vertical force should be added. In addition, the mechanism of mantle uplift is also discussed and the effect of uplift is considered in plane stress problem.

ABOUT THE LOCATION OF DENGZHOU EARTHQUAKE OF 1046 IN SHANDONG PROVINCE

Cai Ke-ming

1987, 9(3):  38-38. 

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A PRIMARY STUDY ON TECTONIC EARTHQUAKE AND POTENTIAL MAGNITUDE——AN EXAMPLE OF "λ"|TYPE STRUCTURE

Pan Shan-de, Du Yi-jun, Ma Jin, Yuan Shu-rong

1987, 9(3):  39-47. 

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So far the potential earthquake magnitude in a tectonic region has scarcely been determined quantitatively. In this paper, we present a method to estimate quantitatively the potential earthquake magnitude. The linearly elastic, plane strain finite element method is used to analyse tectonic stress field. The total strain energy accumulated in the tectonic region and the fracturing area are also calculated. The potential earthquake magnitude is determined by the empirical formula which is related to the strain energy and fracturing area.

PRELIMINARY STUDY OF He/Ar AND N₂/Ar RATIOS FOR GROUNDWATER AND ITS GEOCHEMICAL CHARACTERISTICS

Kong Ling-chang, Chen Wen-ji

1987, 9(3):  48-50. 

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IDENTIFICATION OF FAULT ACTIVITY USING RECENT TOPOGRAPHIC DATA

Huang Xiu-ming, Zheng Bing-hua, Wang Ting-mei, Li Tian-ping

1987, 9(3):  51-60. 

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This paper deals with thrust activity and seismogeologic background at the engineering site. These thrusts occurred in the Yinzhi-Yanshan epoch. The data on test trenches reveal that these thrusts have had not any activity since the late Pleistocene. Analysis of the data on topography around the site shows that these thrusts have had not any activity since the late middle Pleistocene. This site is available to engineering construction in the presence of fault activity.Recent topographic data are useful for identification of fault activity.

LATE QUATERNARY SCARPS AND EARTHQUAKES ON THE MACKAY SEGMENT OF THE LOST RIVER FAULT IN CENTRAL IDAHO, UNITED STATES

Guo Shun-min, Liao Yu-hua, Li Yu-long

1987, 9(3):  61-70. 

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The scarps on the Mackay segment are divided into three groups based on the different amount of displacement and their topographic location. The three groups of scarps suggest three paleoearthquakes. The paleoearthquakes on the Mackay segment had magnitudes of about 7 based on comparing the amount of the displacement and length of scarps. Using the diffusion equation to model scarps on the Mackay segment, the age estimetes suggest that the recurrence interval of magnitud 7 earthquakes is about 5-11 Ka.

CHARACTERISTICS OF GRAVITY FIELD IN THE THREE-GORGE REGION, WESTERN HUBEI PROVINCE AND ITS SEISMOTECTONIC SIGNIFICANCE

Li An-ran, Han Xio-guang, Xu Young-jian

1987, 9(3):  71-78. 

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The deep-seated and major fault with strong activity may cause discontinuty of deep crustal boundary and distribution of anomalous gravity fields, and represent various phenomena by the upper crustal movement. We have calculated crustal thickness by use of gravity data, and then researched further the linear fracture system on the ground surface and the display of present crustal movement in Three-Gorge region, western Hubei province. The authors have come to following conclusion: the gravity anomaly gradient belt trending NNE in Three-Gorge region is not the result of recent deep-seated faulting; the tectonic environment should be not for occurring earthquake in the deep crust.

INDUCED EARTHQUAKES BY INJECTING AND LEAKING WATER IN JIAO 7 OIL WELL, SHANDONG PROVINCE——MACROSCOPIC PHENOMENA ON GROUND SURFACE AND CHARACTERISTICS OF EARTHQUAKE SWARM ACTIVITY

Lu Shau-an, Su Luan-shen, Chen Zhen-ping, Ding Bao-ying, Zhou Quan-shen

1987, 9(3):  79-83. 

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An earthquake swarm induced by injection of water in Dec.1985 in Shouguang County is described and characteristic activity and its generation and mechanism are discussed as well.

INDUCED EARTHQUAKES BY INJECTING AND LEAKING WATER IN JIAO 7 OIL WELL, SHANDONG PROVINCE——CHARACTERISTICS OF THE FOCAL PARAMETERS AND EARTHQUAKE SEQUENCES

Diao Shou-zhong, Zhou Huan-peng, Guo Ai-xing

1987, (3):  84-89. 

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On December 28, 1985, an earthquake swarm was induced by leaking of water of Jiao oil well of the Shengli oil field, Shandong province. By using main parameters of the earthquakes and the source parameters of main shock obtained from the local networks in Shandong province, analysis of the characteristics of geological and sequence. The paper mainly discusses characteristics of the occurring swarm, which is a typical event induced by leaking of water of the deep oil well under the condition of specific geology and low initial stress.

BENTONITE CLAY AND GROUND DEFORMATION

Wu Shao-wu

1987, (3):  90-96. 

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The bentonite clay has been found with a wide area of about ten thousands of square kilometers the behavior of which has been paid great attention for the reason of its damage to engineering structures. However, in this context, a great deal of seismol-ogical research has been overdue.Following available data from the Nanjing seismological station, this paper stresses the importance on this clay in ongoing seismological survey.