Table of Content

02 June 1982, Volume 4 Issue 2

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Brief Report

WARM CONGRATULATION UPON THE 60TH ANNIVERSARY OF THE FOUNDING OF GEOLOGICAL SOCIETY OF CHINA

Broard of Editors

1982, 4(2):  1-1. 

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AN EXAMPLE OF PALEOSTRESS ESTIMATES FROM DEFORMATION INDUCED MICROSTRUCTURES OF QUARTZ IN SHEAR ZONES

1982, 4(2):  2-2. 

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CRUSTAL DEFORMATION AND RECENT TECTONIC MOTION IN THE BEIJING-TIANJING-TANGSHAN REGION

Ying Shaofen

1982, 4(2):  3-10. 

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This paper deals with the recent tectonic motion in this region using the geodetic data, indicating three groups of the most active structures in NNE-NE-NW directions. They have been subjected either to influence of uprising and downfaulting blocks at depth in the earth or to constraint of principal extensional stress field in NNW-SSE direction and principal compressional stress field in ENE-WSW direction, the former being larger than the latter.

ON THE SEISMO GEOLOGICAL TYPES OF STRONG EARTHQUAKES IN SICHUAN AND YUNNAN PROVINCES

Zhang Sichang

1982, 4(2):  11-20. 

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Starting from the analysis of geological background, tectonic features and fracture properties for strong earthquakes, as well as taking the earthquakes in sichuan and Yunnan as examples, we studied the relation between the temporal and spatial distribution patterns and the tectonics for strong shocks. As a result, the stromg esrthquakes were divided into two, A and B, seismogeological types. For type A, the earthquake is due to a continuing fracture. The earthquake-generating structure is a deep and large fault with intensive activity. A variety of earthquake phenomena strictly correspond to the fault. A considerable fracture occurs at a single plane in some direction and appears mainly to be strike-slip. The fracture process behaves as stick-slip. The source fracture can be seen on the ground. The fracture propagates along the fault so as to form a striking linear seismic belt. The seismic energy is released concentrately and the earthquake sequences mostly appear to be mainshock-aftershock type. For type B, the earthquake is due to a newborn fracture. The earthquakes mostly occur in the region where several sets of structure in a fault-block intersacted each other. The fractures often appear in two directions for an earthquake sequence. Some of them appear mainly to be strike-slip, and others dip-slip. But in both of these cases, the fracture process mainly consists of brittle fractures in the rocks. The fracture plane and dislocation are small, and can not be seen on the ground. The energy is released in a decentralized form so that the earthquake sequence appears to have several strong events with comparable magnitude.

A PRELIMINARY DISCUSSION ON THE RELATIONSHIP OF DEEP ENVIRONMENT TO SEISMICITY IN NORTH-SOURH SEISMIC BELT (ITS NORTHERN AND MIDDLE SECTIONS), CHINA

Mao Tongen, Yao Jialiu

1982, 4(2):  21-31. 

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The North-Soath Seismic Belt is one of the most seismically active belts in China. It stretches from the Yinchuan depression in the northern end through the Liupangshan Mts., Qinling Mt., Wenxian, Maowen and along the Hengduan Mts., and far beyond the frontier.In this paper a preliminary discussion is made on the structural features of the crust and upper mantle under the northern (Holangshan-Liupangshan seismic zone) and middle sections (Tianshui-Wudu, Wenxian-North-West-Sichuan seismic zones) of the North-South seismic belt through the geophysical data.The analysis and study of the materials and data available make enable us to recognize the main features of deep seismic environment in northern and middle sections of this seismic belt.1. Top surface of the upper mantle under this seismic belt appears to be in zonal uplift. The axial orientation of the zonal uplift of upper mantle is in NNE direction in the Yinchuan graben area and in NW direction in Xiji, Haiyuan and Guyuan areas, and in sublatitudinal direction in Tianshui-Wudu area.2. The strike of faults along which strong earthquakes occurred and direction of migration of epicenters are coincident with the orientation of isobaths of the top surface of the asthenosphere.3. Strong earthquakes usually took place in the conjunction portion of deep-seated structures with shallow-seated structures at depth in the earth, such as in Tianshui-Wudu area.4. The occurrence of strong earthquakes is related to the local uplifts and depression of the high conductivity layers in the crust and upper mantle.A tentative analysis is made on the relation of the deep-seated environment to preparation of earthquakes. At the end of this paper a discussion is made on the significance of the deep seismic environment in research on medium and long-term earthquake prediction and causes of earthquakes.

ON THE PIEDMONT SCARP IN DILUVIAL FAN OF Mt. HELANSHAN

Zhang Weiqi, Liao Yuhua, Pan Zushou, Song Fangmin

1982, 4(2):  32-34. 

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CHARACTERIZED GROUND WATER ANOMALIES PRIOR TO THE MAJOR SHOCKS AND THEIR PHYSICAL MECHANISM

Feng Xuecai

1982, 4(2):  35-49. 

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The characteristics shared by the ground water anomalies prior to the major shocks occurring in China indicate that the areas of anomalies distribution show a ellipse and four quadrants with a major axis concordant with the seismogenic structures and the iso-seisms. At the magistoseismic area and both ends of it, the changes of anomaly having occurred somewhat late come to a maximum values. For the surroundings of the magistoseismic area the peak of anomaly arising earlier decreases gradually. The change of anomaly shows a tendency to extend gradually toward the epicenter from the surroundings; it goes with an interval, to result in a few of clusters of peaks.We have presented some empirical regularities to determine the epicenter, magnitude, time of earthquake occurrence and the depth of hypocenters in terms of these characteristics in question. It is of practical significance in telling the disturbances from the seismic anomalies. The writer assumed that the predisplacements prior to the quake and the interlayer decoupling are the cause of the ground water anomalies by which the physical process for the development of ground water anomalies may be interpreted. The parameters for the ground water anomalies and the differences in the presence of hydro-geological background have been analyzed by the two mechnisms.

AN EXPERIMENT ON MEASURING RADON BY CONDENSATIONAL MEANS

Zhang Peiren, Wang Jihua, Luo Guangwei, Sun Fengmin

1982, 4(2):  50-52. 

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THE PRELIMINARY STUDY OF SEISMIC STRUCTURES AND THEIR CHARACTERISTIC ACTIVITY IN XINFENGJIANG RESERVOIR AREA

Pan Jianxiong, Xiao Anyu

1982, 4(2):  53-58. 

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The seismic structures in this reservoir area are described in this paper. Based on the data on gravimetric and magnetic survey, vertical deformation of the earth crust as well as the focal mechanism, the activity nature of these seismic structures, the conjugate seismogenic structures, genesis types and their implications in the earthquake prediction are illustrated herein.

CHARACTERISTICS OF LIQUATION OF SON IN THE AREAS WITH VARIOUS INTENSITIES DURING TANGSHAN EARTHQUAKE AND CRITERIA FOR RECOGNITION OF LIQUATION

Wang Kelu, Sheng Xuebin, Chai Lingduo Hu Biru, Liu Huimin

1982, 4(2):  59-70. 

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This paper is to discuss the following aspects of liquafied soil in Tangshan, such as its compositions, properties, morphological features and the changeable regularities. Again, it is pointed out that with the increase of earthquake intensity the mean grain size, sorting coefficient, edge-angle-shaped grains, and the maximum and minimum density and Ga-Na ratio are increasing, but the dense degree, content of organic matter, consolidation degree, and the maximum and minimum porosity as well as rounded grains decreasing.These cases in question are related to the energy released by a shock rather than to the geological and geomorphological conditions.The writers have elucidated some approaches and criteria for recognition of the soil liquation that occurred in regions of various earthquake intensity.The eight physical parameters mentioned above may serve as a recognition indicator by virtue of the features and the regularity of liquation of soil.The diagram and the empirical formula for recognition of liquation of soil are rather important in predicting the liquation of soil and carrying out the zonation of intensity and additional studies of the earthquake disaster.

THE LATE PLEISTOCENE POLLEN ASSEMBLAGE IN THE VILLAGE ZHOUJIAYOUFANG, YUSHU COUNTY, JILIN PROVINCE AND ITS SIGNIFICANCE

Yan Fuhua, Ye Yongying, Mai Xueshun

1982, 4(2):  71-76. 

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The section here concerned is situated in village Zhoujiayoufang, being on the southern slope of a loess terrace between the Songhua and Lalin rivers.A great amount of spore-pollen grains of arboreous, herbaceous and fern plants were found in the sediments of the middle and lower section. They mainly belong to genera Pinus, Picea, Betua, Carpinus, Salix, Artemisia and families Chenopod-iaceae, Gramineae, Umbelliferae or species Betula nana etc.The pollen assemblage described here indicates that the vegetation developed in the v. zhoujiayoufang during the Late Pleistocene time may represent a forest-steppe type.Many cool-temperate plant elements discovered, such as Picea, Bothychium, Betula nana prevanana, imply that in Late Pleistocene time the cold and moist climate was iling in the study area. Therefore, to authors' opinion, the second terrace was formed in the late stage of Late Pleistocene.

DISLOCATION OF THE GREAT WALL IN THE HONGGUOZIGOU, NINGXIA AUTONOMOUS REGION

Liao Yuhua, Pan Zushou

1982, 4(2):  77-79. 

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RULES FROM THE VARIATIONS IN RADON FROM GROUND WATER IN LOG 1^# OF LUNSHI, ZHANGZHOU COUNTY AND THE INFLUENCE FACTORS

1982, 4(2):  80-80. 

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SYMPOSIUM ON SEISMOTECTONICS AND DYNAMICS OF THE EARTH CRUST UNDER THE CHINESE CONTINENT HELD IN BEIJING

Wang Xiaoyuan

1982, 4(2):  84-84. 

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