Table of Content

02 June 1993, Volume 15 Issue 2

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Brief Report

THE CHARACTERISTICS OF SURFACE FAULTING OF 1850 EARTHQUAKE IN XICHANG, SICHUAN

Ren Jinwei, Li Ping

1993, 15(2):  97-106. 

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Various earthquake rupture phenomena along the Zemuhe fault were found through field investigation and the age of them was studied by means of lichen measurement, which proves that the surface rupture zone occurred along the Zemuhe fault with a length of at least 90 kilometers during the 1850 earthquake, the maximum horizontal displacement is 7 meters and the maximum vertical displacement is 5.8 meters. The earthquake faulting caused all kinds of geomorphic and geological features, including fault scarps, fault gullies, offset streams and fans, sag ponds, earthquake wedges, landslides and talus etc. According to the scale and the displacement of the earthquake fault along with historical record, it is suggested that the magnitude of the 1850 earthquake should be 8 and the epicentre should be sited at Daqingliangzi, south of Xichang.

KARAKORUM FAULT AND TAXKORGAN SEISMIC DEFORMATI ON ZONE

Zheng Jiandong

1993, 15(2):  107-116. 

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The Karakorum fault, a major right lateral strike-slip falut in the central Asia is located among Xinjiang, Tibet, Afghanstan and Kashmir, trending NW, with a total length of about 1000km. The Karakorum fault and the Altun Tagh fault creat a large escaping tectonics, which makes the Tibet Plateau moving eastward and has a control on the neotectonics and seismicities of the eastern Asia. The Muji-Taxkorgan basin, a string-like rifted basin is distributed along the western margin of Kongur and Muztagata Mts. A series of active faults lie on the eastern and western margins of these basins. These active faults are characteristic of normal fault. There have been a lot of strong earthquakes and three seismic deformation zones have been found. The Taxkorgan fault is a northern segment of the Karakorum fault, extending NNW.

THE CHARACTERISTICS AND ACTIVITY OF THE CHAERYONG RIVER FAULT ZONE IN KOREA AND ITS RELATION TO EARTHQUAKE

Xia Huaikuan, Lei Qingqing, Xu Dongman, Shi Lanbin, Li Rucheng

1993, 15(2):  117-122. 

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The characteristics of the Chaeryong River fault zone and its relation to earthquakes as well as its recent activity is described in more detail. The fault is proved to be an active fault zone, which may have a control on extending of the fault zone. The formation and evolution of the fault is discussed as well.

STUDY ON ACTIVITY FEATURE AND TIME OF THE FAULTS IN BEDROCK REGION-TAKING KANGDING-MOXI FAULT SEGMENT AS AN EXAMPLE

Liu Xingsong, Xu Huaiji, Shi Lanbin, Tang Hanjun, Ji Fengju, Lin Chuanyong, Guo Jindi, He Yongnian

1993, 15(2):  123-130. 

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To study the activity feature, phase and time of the faults in a bedrock exposing region, a series of samples of fault rocks and fault gouges are collected along the Kangding-Moxi fault segment. TL. ESR. K-Ar techniques,analyses of quartz surface texture and deformation microstructure are used for the comprehensive research. The results show that the fault segment has undergone multiperiodic activity with multiple types (ductile shearing-brittle fracture) and multiple patterns (left-lateral-right-lateral),and the lower limit of the lost strong activity was around the end of late pleistocene or the begining of Holocene (ca. 10000 years).

ANALYSIS OF MECHANICS PROPERTY OF THE MEDIUM UNDER THE DEEP SEISMIC SOURCE ENVIRONMENT ALONG RED RIVER FAULT

Zhang Jianguo, Wang Liangmou, Xu Yujian, Han Yuan100029.

1993, 15(2):  131-137. 

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A method of seismic wave spectrum analysis has been used to investigate the mechanics property of medium under seismic source environment along the Red River fault. The result indicates that there exists an environmental medium condition which is in favor of the creeping slip along the southern part of Red River fault.

PRELIMINARY STUDY OF WAVE VELOCITY (V_p) IN THE ROCKS IN THE DEEPCRUST IN THE NORTHERN HEBEI PROVINCE

Zhang Younan, Li Biao

1993, 15(2):  138-138. 

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MEASUREMENT OF PALEOTECTONIC RESIDUAL STRESS FIELD IN XIANSHUIHE FAULT ZONE AND ITS CONTROL ON LARGE EARTHQUAKES

An Ou, Gau Guebao

1993, 15(2):  139-147. 

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This treatise has accomplished residual stresses measurement of three-dimensions in rock masses in Xianshuihe fault zone, drawn isopleth and principal stress line maps of regional-residual stresses as well as isopleth map of elastic strain energy density field of residual stresses in rock masses in this region and studied the control of this fields on large earthquakes in Xianshuihe fault zone. Based on orthotropic elastic theory of rock mass, the X-ray diffraction method is used in the measurement.

SYMPOSIUM ON TECTONOPHYSICS, HIGH TEMPERATURE AND HIGH PRESSURE, HELD IN CHANGSHA, CHINA

Deng Zhihui

1993, 15(2):  148-148. 

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ISOSTATIC ANOMALIES OF GRAVITY AND GEOLOGIC STRUCTURES OF THE SURFACE AND SHALLOW CRUST

Yin Xiuhua, Liu Tiesheng, Liu Zhanpo

1993, 15(2):  149-156. 

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It is demostrated that feasible is to use isostatic anomalies of gravity to study the geologic structures of the surface and shallow crust according to the isostatic theory and relative experiment. It is indicated that all the reasonable isostasy models may give the same effects, various isostasy models and variations of the model parameters will only result in a little variation in isostatic-correction values of long wave length, and that an evident correlation can be found between the isostatic anomalies of gravity and the geologic structures of the surface and shallow crust. Therefore, it is better to select a simple model for the study of the crustal structure.The best advantage of this method lies in its ability of avoiding the effect of landform configuration to carry out an extense comparison as well as a quantitative analysis.

NEW PUBLICATION——ACTIVE FAULTS IN THE CENTRAL TIBET

Zhong Quan

1993, 15(2):  156-156. 

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FRACTAL DIMENSION OF MAIN FRACTURES OF MARBLE UNDER DIFFERENT EXPERIMENTAL CONDITIONS

Li Biao, Ma Shengli, Zhang Liu

1993, 15(2):  157-163. 

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Marble samples with sizes from ψ20×44mm to ψ90×198mm are deformed in triaxial compression under confining pressures from 10 to 60MPa. The fractal dimension of main fractures is calculated and analysed. D value does not change with sample size when the environment and material conditions are the same, indicating that fracture is of self-similarity. Confining pressure is one of factors affecting D value. As confining pressure increases, D value decreases below 35MPa and increases above 35MPa, suggesting that when fractal geometry of fault traces is analysed in field, the environmental conditions in which the fault is formed and the possible change with depth should be considered.

THE CHARACTERISTICS OF DEHYDRATED AMPHIBOLITE AND THE HETEROGENEITY OF THE LOW VELOCITY LAYER

Gu Zhijuan

1993, 15(2):  164-166. 

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THE ANALYSIS OF MAGNETIC FABRIC OF ROCKS FROM GONGDIANZI FOLD OF QIAN'AN COUNTY, HEBEI

Zheng Min, Yu Qinfan, Tan Chengze

1993, 15(2):  167-173. 

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The characteristics of magnetic fabric of fold rocks has been analyed through determining the synform of magnetic fabric of rocks in Gongdianzi mining area, Qian An of Hebei Province. A simple geological interpretaion of synform structure is made by use of the characteristics of magnetic fabric of rocks.

INVESTIGATION OF CRUST STRUCTURE IN FUZHOU AREA BY MEANS OF CONVERTED WAVES OF EARTHQUAKES

Shao Xuezhong, Gu Zhonghua, Zhang Jiaru

1993, 15(2):  174-180. 

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The method of deep sounding by converted waves of earthquakes was used for the first time in investigation of deep crust structures in Fuzhou area of coast Southeast China. A cross-section of deep crust structure with NE direction and four contour maps of major crust boundaries for the area have been obtained. It is revealed that the Minjiang fault consists of two steep deep-seated faults with NW strike, and that the deep structure of Fuzhou basin is characterized by the belt-shaped subsidence of the boundary G in upper crust and the relative uplift ing of the boundary C, C₁, M and low velocity layer in the middle and lower crust. The results obtained have been served as a basis for the interpratation of the anomaly of high heat flow in Fuzhou region.

EXPLOSION INVESTIGATION OF THE SHALLOW FAULTS AND THE VELOCITY DISTRIBUTION ALONG THE TOP BOUNDARY OF THE BASEMENT IN YUNNAN PROVINCE

Hu Hongxiang

1993, 15(2):  181-185. 

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The data are used to study the P_g phase of three DSS profiles in Yunnan Province, corrected by elevation and diving wave effect. At first, the inversion of their depths has been made by the time field method, then the velocity distribution along the top boundary of basement is evaluated by the sliding average method. The results show that the lateral variation of the boundary valocity is an important basis for investigation of the variation of the rock property. It is also a method to judge the existence and the character of faults. Where the lateral variation of the boundary velocity occurs suddenly there is usually some influence of the fault. Many faults in these profiles are in evidence this way. Some great faults are accompanied by depth changes of interfaces or distortions of the isochrones.

DETERMINATION OF SAND SOIL LIQUEFACTION UNDER COMPLEX SITE CONDITION

Yao Daquan

1993, 15(2):  186-192. 

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The procedure for determination of soil liquefaction in general sites is systematicly introduced as well as how reasonably select the criterion of sand soil liquefaction under complex sites,taking the various factors into consideration.Discussed here is an effctive method available for predicting the liquefaction of sand soil, especially for the important engineering projects, along with the example of the liquefaction of the bridge foundation. The depth to which the liquefaction of soils may be generated is disscussed as well, allowing for some relative effects of the geologic harzards in regard to the liquefaction and collapes.