Table of Content

05 March 1986, Volume 8 Issue 1

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Brief Report

ACTIVE TECTONICS AND STATE OF STRESS IN SEISMIC REGION OF NORTH-WEST YUNNAN PROVINCE, CHINA

Liu Guangxun, Li Fangquan, Li Guirong

1986, 8(1):  1-14. 

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The active tectonic pattern and recent stress state in the seismic region of NW Yunnan province are discussed on the basis of field observation and in-situ stress measurements.Data.show that this region is characterized by pull-apart structures which are formed by the movement of two right-lateral strike-slip faults,the Red River and the Zhongdian fractures,and that the crustal stress state in this region is different from those in the surrounding areas.The earthquake distribution in time and space is controlled by the tectonic pattern and relevant stress states.

RECENT TECTONIC STRESS FIELD IN THE NORTHWEST OF THE YUNNAN PROVINCE

Xiang Hougfa, Guo Shunmin, Ran Yongkang, Li Xianggen, Zhang Jing, Chen Tieniu, Zhang Guowei

1986, 8(1):  15-23. 

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The comprehensive characteristics of active faults,physical mechanism of fault basins,pole direction of drainage system and fault plane solution of moderate and small earthquakes indicate that recent tectonic stress fields in the study area trend from NNW to nearly SN.It follows that local tectonic stress fields in the area is related to the tectonic deformation of upper crust,caused by slipping to the south of Sichuan-Yunnan block in which the fault basin in the area has been a pull-apart basin of the surface crust since the Neogene.The boundary faults of the basins tend to be in the form of the shovel and to be down to at a depth of 1-2 km,and moderate/small earthquakes are concentrated at a depth less than 20 km,which suggests a strain release of two sorts at different depths in the slipping process.It is possible that the lower part of the crust is in the process of being deformed to northeast between the large-scele platas.Earthquakes of >M 6 with characteristic of high-angla strik-slip mainly concetate at a depth of 20-25 km which is partly related to NE compressive stress.The intersection of large-scale and local stress fields may be representative of tectonic stress at different depths.Of course,the Hounghuo River fault zone in the presence of shear-tension obviously has an effect on shifting of the stress field direction of this region.

FIELD INVESTIGATION OF STRONG MEXICO EARTHQUAKE OF M=8.1

Zhu Haizhi

1986, 8(1):  24-24. 

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QINGHAI-XIZANG PLATEAU LINEAMENTS AND THEIR CHARACTERISTIC ACTIVITIES

Zheng Binghua

1986, 8(1):  25-32. 

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The convergence of Indian and Eurasian plates,especially the crustal activity in the Qinghai-Xizang Plateau has attracted geoscientists attention.This paper atempts to use the advantage of wide-sight and continuity of view on the Landsat images to analyse the spatial distribution of the lineament and their geometric patterns for avialable information.Combined with geological,geophydical and seismological data,a further investigation is made for the main characteristics of the acnvitity of blocks and their boundary faults in the plateau and their generations.

INTERNATIONAL SYMPOSIUM ONESR DATION

Lin Zhuoran

1986, 8(1):  32-32. 

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COLLATION FOR THE SOUTHERN-YELLOW SEA SEISMIC BELT AND THE SOME PROBLEMS RELATING TO SEISMICITY

Zhu Shujun, Sun Shoucheng

1986, 8(1):  33-39. 

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The authors have come to some conclusions about distributions of epicenters(M≥5).strain release and modern characterized crustal activity on the basis of comparing seismi-cities between the Southern-Yellow Sea area and the Yangzhou-Tongling seismic belt.The seismicity level of the Southern-Yellow Sea area is much higher than that of the Yangzhou-Tongling seismic belt,suggesting a new seismic belt along the study area.The study area can be regarded as an independent seismic belt.Some main characteristics of the seismicity in the Southern-Yellow Sea area has been studied as well.

"ATLAS ON THE LITHOSPHERIC DYNAMICS OF CHINA" HAVE COME TO AN END

Bian Tu

1986, 8(1):  40-40. 

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LANDFORMS OF THE COASTAL AREA OF THE LIAODONG DENINSULA AND THEIR REPRESENTATIVE NEOTECTONIC MOTION

Xia Huaikuan, Zhang Xianze

1986, 8(1):  41-49. 

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Statistics of the "order" of the landforms and their elevations have been carried out from 126 coastal terraces sections for the study area.The authors suggest that the marine landforms might take their forms in the mid Holocene time,and.the marine-erosion terraces of W "order",in the geological context of pleistocene.The results from the research of this kind indicate that the Yalu Jiang fault and the Jingzhou fault are the major active faults in the study area.The authors also indicate that there may be a genetic relationship between the coastal terraces in question and marine terrace along the lower reaches of the Liaohe,theirrelative motion being quantitatively determined.

"MEETING ON SEIENTIFIC WORK OF HISTORICAL EARTHQUAKES"|HELD IN HONGZHOU

Yao Yanzhi

1986, 8(1):  50-50. 

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PRELIMINARY RESEARCHES ON THE EFFECTS OF HYDROGE-OCHEMISTRY CAUSED BY EXPLOSION OF TWO TYPES

Yu Zhaokang, Cai Shihuang, Lin Jiatao

1986, 8(1):  51-58. 

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In this paper,we based ours researches on the great deal of observation data on the hydrogeochemical effects,all of which were obtained from three surface explosions in the copper ore region of Yongping,Jianxi and two deep-well-explosions in Longhai,Fujian.It is believed that the explosive impulse force take an important role in various chemical changes in the components of Rn and other hydrochemistry.The effect of hy-drogeochemistry caused by explosions are necessarily associated with geological structures,hydrogeological conditions and geochemical environment in observation points.Based on this theory,the preseismic hydrogeochemical mechanism is discussed and studied.

CHARACTERISTICS OF PETROLOGY OF THE DATONG BASALTS

Zhang Yanpo

1986, 8(1):  59-67. 

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For the Datong basin Quaternary volcanic group can be subdivided into two parts:the northwestern area (i.e.the Datong volcanic group) and the southeastern area.The volcanoes in the northwestern area are typical of the central eruption with basaltic lavas of alkaline olivine basalts and ones in the southeastern area of fissure effusion with basaltic lava flow mainly consisting of olivine tholeiites.This paper studies difference between volcanic rocks in the two areas on the basis of petrology,geochemistry,rare earth elements,trace elements and their charactristics.

"SYMPOSIUM ON NAPPE STRUCTURES AND REGIONAL STRUCTURES"|HELD IN NANJING

Wang Xiaoyuan

1986, 8(1):  68-68. 

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GEOLOGICAL ACE AND ENVIROMENT OF THE DAHOCUN SITE, ZHENGZHOU, FROM SPORO-POILEN DATA

Yan Fuhua, Ye Yongying, Mai Xuishun

1986, 8(1):  69-74. 

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The site under study is situated in northeastern Zhengzhou.Many pollen grains of arbor,shrub and herb have been found in sediments.Arboreous pollen grains are mainly of coniferales including the genera Pi-nus and Betula etc.,and sh-rub and herb pollen of Ephedra,Artemisia,Chenopodiaceae and Compositae.On th basis of obtained results it is believed that the Dahocun site was once covered with a forest steppe vegetetion;the climate had a change as the site formed.In the early stage the prevailing climate was warm and humider;in the middle stage,warm and moist;in the late stage,warm and drier.Poynological date and ¹⁴C age indicate local sediments as the Middle Holocene for the lower and middle parts and the Upper Holocene fer the Upper part.

DISSCUSSION ON TECTONIC STRESS FIELD IN THE NORTH CHINA PLATFORM WITH HYDROFRACTURING DATA

Liu Jianzhong, Li Zhiqiang

1986, 8(1):  75-81. 

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This paper deals with the stress field in the North China platform and has come to a conclusion that this area shows a difference of the horizontal stress in depth,higher in the eastern part and lower in the western part.Principal horizontal stress from various observation points increases with the depth in this area as well as in the Ordos uplifting region.In addition,the extensional stress appearsat a depth of 500 m.For the Beijing-Tianjing-Tangshan-Bohai area,the maximal principal compressive stress in depth is of ENE or nearly EW direction.At a depth of 30m from the surface the stress orientation relatively scatters and increases with depth below 30m,whereas shows a tendency of rotating.Decreasing of the minimal horizontal principal stress,or more,may he responsible for a trigger of the earthquake associated with a change in stresses.

"SYMPOSIUM ON VOLCANIC AND SUBVOLCANIC ROCK AND METALLOGENESIS",HELD IN HANGZHOU

Yao Yanzhi

1986, 8(1):  82-82. 

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ASPERITY OF SLIDING ZONE AND TWO DIFFERENT KINDS OF SUDDEN INSTABILITIES IN ROCKS

Wang Shengzu, Shi Liangqi

1986, 8(1):  83-93. 

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There are two modes of sudden instabilities in rocks,i.e.low-and high-pressure sudden instabilities.The substantial difference in mechanism between them is the "nonuni-form-" or "uniform-resistance" during sliding,and the asperity of sliding surface is one of the important factors which results in the non-uniform resistance and influences the mode of instability.The corresponding criteria for different modes of instabilities have been established in this paper to reflect the effects of environmental stiffness,contact stiffness and nonuniformity of sliding resistance.The strong shallow earthquake is principally a process of high-pressure sudden instability.It is emphasized that apart from the quasi-static strength condition the environmental stiffness,the uniform-resistance and other conditions are necessary for the occurrence of strong earthquake.

FREQUENCY ANALYSING SYSTEM OF ACOUSTIC EMISSION SIGNAIS

Wang Tongjun, Zhao Shuqing

1986, 8(1):  94-96. 

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