Table of Content

05 June 1991, Volume 13 Issue 2

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Brief Report

SPATIAL DISTRIBUTION AND FRACTAL STRUCTURE OF AE FOCUSES OF INADA GRANITE UNDER TRIAXIAL COMPRESSION

Lei Xing-lin, Ma Jin, Kusunose K., Nishizawa O., Satoh T.

1991, 13(2):  97-114. 

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An experimental study on the spatial distribution of the focuses of acoustic emissions of Inada granite (coarse grained granodiorite) under triaxial compression is reported in this paper. It is pointed out that AE locations is fractal with a dimension of 2.2 in average,lower than the result of Oshima granite (fine grained granodiorite),which is 2.7,under similar deformation condition. For Inada granite a band-limited fractal had been observed. Fractal dimension changed around grain size of the rock (R_C=5mm) Fractal dimension D_s and D_l (below and above the grain size,respectively) had different developing tendency. D_s and D_l can be considered as indicators of the inhomogeneity of stress field in corresponding scale.

STUDY ON ELECTRIC CONDUCTIVITY OF THE DEEP EARTH ALONG THE YIXIAN, LIAONING, TO DONG-UJIMQIN, NEI MONGOL FROM PROFILE

Shi Shu-lin Xu Chang-fang, Wang Ji-jun, Sun Jin, Jiang Zhao, Zhang Yu-hui

1991, 13(2):  115-125. 

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The magnetotelluric sounding profile from Yixian,Liaoning,to Dong-Ujimqin Nei Mongol,was carried out and the geoelectrical structure along this profile is presented in this paper. The results show that the buried depth of the conductive layers both in the crust and upper mantle is in a good correspondence with geotemperature field data i. e. The shallower the buried depth of the conductive layers,the higher the heat flow value.According to the geoeletrical structure it is supposed that the Siramulen River fault zone seems to be a tectonic suture line between Siberia plate and China plate.

A NEW METHOD FOR DIVIDING THE EXPANSIBILITIES OF SWELLING SOILS

Zhang Xin-hai

1991, 13(2):  126-128. 

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PRECENOZOIC GEOTECTONIC FRAMEWORK AND EVOLUTION OF THE ZHEIJ IANG-FUJIAN AND ITS OFFSHORE

Tao Guo-bao, Zhu Ping, Liang Lian-xi

1991, 13(2):  129-137. 

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On the basis of views of predecessers about the geotectonics in Zheijlang-Fujian on-land and its offshore,we proposed our opinion by terrane theory according to the information of geology,geophysics and radiometric age etc. This is a complex collision tectonics region of Precenoozic terranes,which can be divided into several elements from west to east,as follows: northwest Fujian terrane,Longquan collision zone,southeast Zheijiang、terrane,costal collision zone and Wen Don terrane. Zhoushan-Pinghu fault zone is a transverse fault (or an ancient transform fault),which separates this region from the north terrane which is fundamentally different in geology and geophysics. The Precenozoic evolution of the geotectonics in the region has undergone a very complex history of terrane drifting,collision juxtaposition and jump of subduction zone.

AN INVESTIGATION ON GEOMORPHOLOGY AND QUATERNARY DEPOSITIONS FOR ACTIVITY OF THE SHENZHEN FAULT ZONE, GUANGDONG PROVINCE

Lu Yan-chou, Sun Jian-zhong

1991, 13(2):  138-146. 

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Activity and neotectonics of the Shenzhen fault zone in the Shenzhen Special Economic Zone,Guangdong Province,has been discussed on the basis of geomorphic features and Quaternary sediments,as follows:1. There is a series of the smaller intermontane basins and valleys,with axis orientation of NE-SW or ENE-WSW same as trending of the major faults within the fault zone. Most of these basins and valleys,in which the colluvium,alluvium and swamp deposits,with a total thickness of less than 10-15m,were accumulated during the period from the middle of the Late Pleistocene to the middle of the Holocene,are located in the older fracture and or the limistone strata undergoing karstification strongly. Their distribution,hence,might be related to the faulting processes before the Late Pleistocene. However,any fault and marked deformation in the sediments of the Late Pleistocene and Holocene has not been observed. It may be suggested that no remarkably faulting has occurred in the fault zone at least since the middle of the Late Pleistocene.2. Four paleo-denudation surfaces and three alluvium tarraces have been developed in the fault zone since about 1.8 Ma. The vertical deformation rates of crust uplift relative to the regional erosion basis could be estimated as 0.04-0.2mm/a for different ages,based upon the elevations and duration estimates of the geomorphic surfaces formed in different stage. The Quaternary tectonic movement would be characcterized by pulse uplift and depression of the crust for the Shenzhen fault zone.

THE DISCOVERY OF DEXTRAL STRIKE-SLIP IN HOLOCENE ALONG THE TANGTO FAULT IN SHANDONG PROVINCE

Jiang Wa-li, Liu Zhong-wen, Li Xian-ye, Li Qing-shan, Fan Wen-kui

1991, 13(2):  147-151. 

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The fault scarp of the Tangto fault is 36 km long,1 to 3m high,striking NE15?. Its east side has been uplifted. The fault scarp in ground surface approximately is along the fault face that consists of Cretaceous sandstone and Archaean gneiss. Twelve gullies which strike nearly EW were dislocated in right lateral mode by three left-stepping echelon secondary faults in 1.1km distance,in the vicinity of Juquan village,where the gullies are contorted with right angle or their lower and upper reaches are offset. The horizontal dislocation is 3-25m. The biggest is in middle,the smaller is in either end of the fault in one of the three secondary fault. In a place along the fault,it has been discovered that the peat which has a few square metre has been uplifted. Its position is about 2.0m to the bottom at present. It is considered that the peat was the early sediment in the pool along the fault scarp. The 11G dating of the peat is 3681 a B.P. and two faulting can be shown. One occurred before 3681a probably and the other is the dextral strike slip faulting occurring in last 3681a. If creep-slip is not in consideration,two earthquake events would have occurred since Middle-Late Holo-cene.

INDICATIONS OF TECTONIC MOVEMENT IN NORTH CHINA BEFORE 1976 TANGSHAN EARTHQUAKE

Li Jian-hua, Li Wang-zhou

1991, 13(2):  152-160. 

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The authors have comprehensively analysed 18 sets of 630 Landsat photos of different time phases and wave bands for North China. It is revealed that before the occurrence of 1976 Tangshan earthquake various indications of tectonic movement,including those of compresso-shearing and extension,appeared on Landsat images. These indications occurred 13-16 months before 1976 Tangshan earthquake,and thus can be considered as midrange precursors of earthquake. It is suggested that the monitoring of such indications of tectonic movement in Beijing-Tianjin area and other sensitive points by using Landsat data collected by satellite ground station,will be of great importance to the capture of midrange seismic precursors and thus to the seismic harzard reduction itself.

A STUDY ON TECTONIC STRESS FIELD ON THE MIDDLE SECTION OF NORTHERN QINLING MOUNTAIN IN SHAANXI PROVINCE

Xu Wen-long

1991, 13(2):  161-172. 

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Obtained from the displacement of the microfaultssystematically measured along the middle section of northern Qinling on the southern borders of the North China Plate in Shaanxi Province by use of a method for fitting data of the fault-slip vector were the means stress tensors of the tectonic stress field since Cenozoic time. Three plases of stress field are:1) the stress relaxation in the direction of NW280-310?,2) the compression in the direction of NW305-310癮nd 3) the relaxation (NW 294-340?) along with a secondary compression in the direction NE 21-68?. The result indicates that the characteristics of the third phase of the stress field in the area is essentially consistent with that of the regional stress field in the North China Plate.

THE SPACIAL RELATIONSHIPS OF THREE STRONG SEQUENTIALLY OCCURRING EARTHQUAKES

Deng Zhi-hui, Ma Jin

1991, 13(2):  173-178. 

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The spacial relationships of strong earthquakes have been investigated for two catalogues: Chinese historical earthquake catalogue(M≥7) and worldwide earthquake cat-alogue(M≥7) from 1900 to 1980. Three strong earthquakes taking place one after another are labeled as A,B and C. The spacial relationship between A,B and C are revealed through systematical statisical analyses. (1) The preferential distribution of ABC planes is to intersect the upper part of the asthenosphere or the lower part of the lithosphere. (2) After earthquakes A and B,both extending regions from A to B or from B to A,and the place between A and B ((ΔCA-ΔCB)/ΔAB≈-0.2),are more risk regions then the other regions. Based on these spacial relationships,strong earthquakes can be predicted in probability. The 56 groups of Chinese historical strong earthquakes (M≥7) have been calculated. Most of earthquakes (C) in each group took place in the high probability regions.

RADIOCARBON DATING OF LATE QUARTERNARY SEDIMENTS IN ERHAI LAKE BASIN OF DALI AREA AND EVOLUTION OF THE ERHAI LAKE

Peng Gui, Jiao Wen-qiang

1991, 13(2):  179-183. 

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This paper deals with the evolution of the Erhai Lake that have occurred since middle of late Pleistocene on the basis of distribution of lacustrine facies sediments in the western plain of Erhar Lake basin. and with the radiocarbon age determination of relevant sediments and archaeological data.The research indicates that the ancient bank line of the western part of Erhar Lake shifted from west to east 50 thousands years B.P.. During this period if oscillated several times.The main factor causing the shift of the bank line are the intermittent uplift of the Canshan block and the intermittent subsidence of the Erhai Lake basin.The climattic change in geologic history has also played an important role.

CHINA PALEOMAGNETIC DATA LIST FOR CENOZOIC

Cheng Guo-liang, Sun Yu-hang, Li Su-ling

1991, 13(2):  184-186. 

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ANALYSIS OF THE RESPONSE OF WATER LEVEL IN WELL LU-15 TO THE PROCESS OF MINE COLLAPSE

Zhang Zhao-dong, Jing Ji-cai, Zheng Jin-han, Zhang Zuang-cheng

1991, 13(2):  187-192. 

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Evident is the response of water level in the well Lu-15 to the process of mine collapse. Tentative analysis shows that using some precursory phenomena before a bigger mine collapse,a prediction of earthquake for the bigger mine collapse will can be made. For instance,the active time of less collapse before the bigger collapse will increase; the average change of water level in the well in each active period,the duration time ine ach active period and each calm period will all change before the bigger collapse: the abnormalities in the ΣN-t and No-Δt curves will all appear 28 days before the bigger collapse.