Table of Content

07 June 1995, Volume 17 Issue 2

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Brief Report

STUDY ON THE SEISMIC PHASE OF DSS NORTH CHINA

Jia Shixu, Liu Changquan

1995, 17(2):  97-105. 

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In this paper, We have studied the four(P_g,P_c,P_m and P_n)routine phases of DSS in North China and their implications for the structure and physical characters of the crust and upper man-tle. Those phases show the structural feature of the different lavers as well as the velocitv and the velocity gradient changes of both vertical and lateral direction. We have also researched the sin-gular phases and their specialities and important implication for the crustal structure. The singu-lar phases with anomaly of the appearent velocity,amplitude and appearing interval can be found in some profiles. The result indicate that the singular phases reflect the crustal structure anoma-lous characters related to the preparation of strong earthquake and mineral resoucres.

THE REASON FOR SUCCESSIVE DECREASING OF WATER LEVEL IN THE TONGXIAN WELL

Yang Huinian

1995, 17(2):  106-108. 

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STUDY OF GKAVITY ANOMALY IN CRUSTAL LOW VELOCITY ZONE IN THE WUTAI REGION

Fan Shengming, Yu Qingfan, Lou Hai, Xing Jishan

1995, 17(2):  109-113. 

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This paper deals with three dimensional inversion of low density(low velocity)anomalous zone in the middle and lower crusts in the Wutai region by use of the method of robust maximum likelibood to obtain its spatial existence for this anomalous zone and to carry out a geological in-terpretation along with shallow local negative anomaly of gravity as well as other geophysical characteristics. Their mechanism has been descussed as well.

A VIEW ON THE BOUNDARY OF THE JIAONAN-RONGCHENG COLLIDING ZONE ALONG THE EASTERN SEGMENT OF THE QINLING OROGENIC BELT

Wang Peicheng

1995, 17(2):  114-115. 

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SEGMENTATION AND RISK ESTIMATION AND RISK EQRTHQUAKES ON QILANSHAN ACTIVE FAUL ZONE

Chu Quanzhi, Wang Liangmou, Guo Shunmin

1995, 17(2):  116-122. 

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Qilianshan active fault zone is situated in the northeastern border of Tibet Plateau.It con-sists of North Qilianshan fault and Haiyuan fault. It is mainly a compressive-sheared and sinis-tral-slipping fault zone,its slip rate at most up to 9mm/a。Many ancient earthquakes and histori-cal earthquakes occurred in the zone.On the basis of the active behavior of the fault zone,three sections and seventeen segments were divided.According to the relation of ancient earthquakes,slip rate and length of segrnents,a bivariate regreession model was set up. The evalution of risk was made. Finally,we can disfinguish between three risk segments of type A and four risk seg-ments of type B.

PLASTIC-FLOW WAVES AND EARTHQUAKE MIGRATION IN CONTINTAL PLATE(Ⅱ)

Wang Shengzu, Zhang Zongchun

1995, 17(2):  123-131. 

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Based on the concepts of plastic-flow network and plastic-flow waves in the continental lithosphere, migration of earthquakes is essentially their moving along”plastic-flow/seismic”belts in network system controlled by the plastic-flow waves. In terms of the inference from the time-space distribution of earthquakes, there are at least two sorts of plastic-flow waves in the central and eastern Asian network svstem, such as the“decade-wave” and” century-wave” in-volving the interrnediate-range prediction of earthquakes. They are of different wave-originated times, wave-originated stages, and wave-crest belts,and different preferential propagation directions and effective action ranges for each stage. The overlapping of the two sorts of wave-crest belts forms the double wave-crest areas in which the portion covered by ” plastic-flow/seismic”belts becomes the energy background areas necessary for earthquakes. It is indicated by examining the situation in 1976 that about 90% of 19 earthquakes with magnitudes ranging 6.0 to 7.9,or about 83%of 6 groups of these earthquakes,distribute in the energy background areas with the corresponding earthquake magnitude ranges.

SYNTHESIS OF POLYCRYSTALLINE AGGREGATES USING SINTERING-HOT PRESSING METHOD IN A PISTON CYLINDER

Wang Zichao

1995, 17(2):  132-138. 

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Synthesis of polucrystalline aggregates using sintering-hot pressing method in a piston cylin-der apparatus was introduced. We discussed in detail the technique and the mechanisms of sample densification with forsterite as an exarnple. The results showed that polycrystalline aggregates with a few centimter in size and desired chemical and mineral compositions can be synthsized.These synthesized polycrystalline aggregates were of high density(up to 98%of its theoretic density)and homogenous texture and can be used for various purposes in geoscientific research.

TREE SELSMOLOGICAL STUDY OF ACTIVE GULANG AND JINGTAI FAULT IN GANSU PROVINCE

Yang Bin, Liu Baichi, Zhou Junxi

1995, 17(2):  139-147. 

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On the bases of technical study of tree ring dating,several hundreds of trees growing along the western part of Gulang active fault were determined and evaluated.The growing rates oftrees and the three types of lower ring ratios have been identified effectively. The results show that the abnormal ring structures and growing rate of the Qinghai cryptomeria fir on the fault scarp were caused by the Gulang M8.0 earthquake on May 23,1927,which gives exact evidence for the dating of Gulang seismogenic fault and moved the location of this fault along the northern foot of Lenglongling to the south by 30km. The research mentioned above has also been applied successfully to the dating of the fracture belt caused by the Jingtai M6¹/4 earthquake on Novem-ber 2,1888,along the northern foot active fault of Laohushan mountain.

ELEVATION DISTRIBUTION OF MARINE SEDIMENTS DURING THE LATEST PREVATEST PREVAIL GLACIAL AGE AND TNEIR RELATIONSHIP TO EARTHQUAKES IN SOUTHEAST CHINA COAST——A QUESTION OF THE LOWEST GLOBAL SEA LEVEL DEEPER THAN 100m

Xu qihao, Huang Zhengguo

1995, 17(2):  149-157. 

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The littoral sediments during the latest prevailing age(21～14kaB.P.)along southeast China coast aredistributed between 3 8m above sea level and-50m below sea level.There is an evi-dence that strong earthquakes changed the original position of this sediment so that it was dis-persed at different elevations. The degree of dispersion corresponds to the intensity of earthquake──the more the dispersive marine sediments in elavation,the stronger the earthquakes.Therefore the sea level in that period was not at 100m below the present sea level,i.e.-100m.A subsidence of the crust or earthquakes.

FEATURES OF DUCTILE SHEAR ZONE AND MYLONITE ALONG THE NORTHERN SLOPE OF MOUNT QOMOLANGMA

Shi Lanbin, Lin Chuanyong, Chen Xiaode, Zhang Xiao'ou

1995, 17(2):  158-161. 

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ON INFLUENCE OF STRESS AND THERMAL FATIGUE ON KAISER EFFECTS OF GRANITE

Xi Daoying, Chen Pugang

1995, 17(2):  162-166. 

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Rock may lose its memory property if it has undergone loading and heating process frequent-ly.Because these frequent actions can cause a lot of damage in the rock. All kinds of interference must be disposed if we use the Kaiser effect to determine the geostress and heat states of the rock.

THE UPPER MANTLE SHEAR ZONE OF YITONG GRABEN

Zhang Xiaoou

1995, 17(2):  167-176. 

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This paper has studied the deformation features of the mylonitic mantle xenolith,including deformation-induced microstructures,dislocation substructures and fabric. It is confirmed that mylonitic mantle xenolith is representative of upper mantle shear zone. The physical conditions ofthe formation of upper mantle shear zone have been determined as T=729～828 ℃,P=1.10～1.38GPa,σ₁-σ₃=97～150MPa,ε=10^-14～10^-12s^-1,η=10～1000EPa·s,Z=37～45km.Based on these results,it is suggested that the shear zone is a small-scale gently dipping shearzone,which is related to the mantle diapir and is a zone of strain concentration, which causes theseismic anisotropy of upper mantle and is presumably related to the seismicity of the region.

MICROSCOPIC MARKS OF STICK SLIP AND CREEP SLIPPAGE IN DEFORMATION PRODUCTS ALONG THE TANCHENG-LUJIANG FAULT ZONE(JUXIAN ZHAOXIAN～SUQIAN XIAODDITN)

Yao Daquan, Tang Youbiao, Li Jie, Liu jiacan, Gao Yufeng, Bao Sifa

1995, 17(2):  177-184. 

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Based on orientated sampling of deformation prod ucts in Juxian Zhaoxian～Suqian Xiaodian of the Tancheng-Lujiang fault zone, undisturbing and indurating sampling, the micorscopic ob-servation has been conducted, along with results of rock-breaking test and microsopic analysis.The authors come to conclusion of microscopic marks of stick slippage,reprsentative of kinetic characteristics of the fault zone. Outlined some problems in this regard have been discussed aswell.

FRACTAL RESEARCH OF GRANULOMETRIC COMPOSITION IN FAULT GOUGE

Yi Shunmin, Tong Huaming

1995, 17(2):  185-191. 

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In this paper, fractal structure features of granulometric composition in fault gouge are stud-ied based on fractal theory. The result shows that fractal dimension of fault gouge changes from 2to 3,and its average value is about 2.8.Fractal dimension is a parameter describing the granu-lometic composition of fault gouge. The largger the fractal dimension value,the higher, the de-gree of self-organization. The evolution of fault gouge is in a higher stage. The author discusses the relationship between fractal dimension,indexes of physical mechanical property of fault gougeand features of fault motion.