Table of Content

11 December 1990, Volume 12 Issue 4

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Brief Report

A STUDY ON RUPTURE ZONE OF THE 1988 GENGMA EARTHQUAKE WITH MAGNITUDE 7.2 IN YUNNAN PROVINCE

Zhou Rei-qi, Yu Wei-xian, Gu Yi-shan, Yao Xiao-zhi

1990, 12(4):  291-302. 

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In this paper from the data of field investigation,a surface rupture zone of the Ge-ngma earthquake in Yunnan Province is studied. Meanwhile,a dislocation model of the tension-torsion fault type is suggested from the data on fault dislocation. It is shown that the seismogenic structure for the Gengma earthquake is dominated by right-lateral horizontal offset with horizontal extension. The maximum dislocation is 1.6 meter and the maximum strike slip is 0.96 meter. The preferred direction of sliding vector is NW-SE 55°at a dip angle about 30—40°. The result of stress analysis suggests that the preferred direction of principal compressive stress is N5—10° E at an elevation angle about 40—60° in the earthquake area.

FOCAL STRESS FIELD BY WATER INJECTION-INDUCED EARTHQUAKES AND CHARACTERISTICS OF CODA WAVE ATTENUATION

Zhao Gen-mo, Yang Gang-sheng

1990, 12(4):  303-310. 

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The focal mechanism solution,the coda wave value Q and the stress drop were obtained for the water injection-induced earthquakes with M_L>2.0 which occurred in a period from sept. 1986,in the Renqiu oil field of North China.The obtained result indicates that the focal machanism of induced earthquakes under the effect of movement along the primary fault close to water injection well is different from that of natural earthquakes. The average coda wave value Q₀ is 75 within the oil field which is smaller than that in the neardy areas. The stress drop by induced earthquakes changes from 0.2 to 3.0 bars. It shows that the stress background level in the oil field is not high.

Comprehensive Study of the Crustal Stress Field in publication

1990, (4):  310-310. 

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Brief Report

P-WAVE Q-VALUE OF ACOUSTIC EMISSION IN FRACTURE PROCESS OF GRANITE SPECIMENS UNDER TRUE TRIAXIAL COMPRESSION

Miao Jun, Xu Zhao-yong, Han Ming

1990, 12(4):  311-315. 

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Yinjiang granite specimens 50?50? 100mm³ in size are tested under true triaxial compressions of σ₃=30 MPa,σ₂=60MPa and increasing σ₁ until the specimens fracture. We determined the P-wave Q-value of acoustic emission in σ₃ and σ₂ directions in the fracture process of specimens from the wave propagation and the spectral amplitude ratio. The obtained result shows that P-wave Q-vaiue and spectral amplitude of acoustic emission show their significant characteristic variation,which are anisotropic. We found an abnormal phenomenon:after σ₁>0.95σ_IP,for the amplitudes of waves emitted from same source,those which are received by near probe are smaller,and those which are received by far probe are larger.

A STUDY ON STRUCTURE OF THE DEEP CRUST IN TAIWAN REGION

1990, 12(4):  316-316. 

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SURFACE RUPTURES BY EARTHQUAKES FOUND IN XAINZA,CENTRAL XIZANG

Wu Zhang-ming, Cao Zhong-quan, Shen-tu Bing-ming, Deng Qi-dong

1990, 12(4):  317-318. 

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NUMERICAL SIMULATION OF CONTEMPORARY CRUSTAL BLOCK MOTION IN CHINA AND SUROUNDING AREA

Hong Han-jing

1990, 12(4):  319-331. 

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The relative motion of crustal blocks in China and surounding area has been investigated using a geometric method,which was engaged in study of plate motion by Minster & Jorden (1978). Although the crustal block is a distinct geological element from the lithospheric plate either in their involved depths or in the driving forces,bu both of them are comparatively rigid blocks separated by mobile belts. From the slip rates along active faults on the block boundaries,the Euler poles and angular velocities of 14 blocks were calculated using least square method. The calculated displacement velocities of the crustal blocks indicate that the slip rates along active faults are determined by the motion of their adjacent blocks,and the collision between Eurasia and Indian plates plays dominant role in crustal deformation in this area.

TEMPORAL DISTRIBUTION OF RUNOFF IN LOWER HUANGHE RIVER BASIN AND STRONG EARTHQUAKES IN NORTH CHINA

1990, 12(4):  332-332. 

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A PALEOSEISMOLOGICAL PROFILE ACROSS PIEDMONT FAULT ZONE AT TAIPINGKOU ON NORTHERN SEGMENT OF QINLING MOUNTAINS

Zhang An-liang, Zhong Jin, Min Feng-shou

1990, 12(4):  333-334. 

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EXPERIMENTAL STUDY ON SEMI-BRITTLE BEHAVIOR OF ROCKS AT TEMPERATURE AND PRESSURE CORRESPONDING TO MIDDLE-LOWER CRUST

Wang Zi-chao, Wang Sheng-zu

1990, 12(4):  335-342. 

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This paper deals with some results of experimental study on semi-brittle behavior of rocks at the conditions relevant to the middle-lower crust. By observing and analysing macro-characteristics of deformed granite,gabbro and quartzite,such as creep curve,creep type,relationship between creep rate and time,creep deformation,steady-state creep rate and flow stress,as well as creep failure features,some basic regularities of semi-brittle rock creep are recognized. From the obtained data a semi-brittle creep mechanism map in flow stress-temperature and pressure space is suggested for predicting the potential semi-brittle creep behavior of rocks in the Earth's crust.

PRELIMINARY STUDY ON SPATIAL RELATIONSHIP BETWEEN EARTHQUAKES AND HOT SPRINGS ON LIAODONG PENINSULA

Zhong yi-zhang, Xiao Xiu-qing

1990, 12(4):  343-350. 

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The liaodong Peninsula is an area with a large amount of hot springs and frequent earthquakes. 41 hot springs with temperature over 20℃ were found by the end of 1984. Their distribution is controlled by many factors,such as the faults,lithologic fealures,geomorphologic elements,etc.The regional seismicity is mainly monitored by the seismic networks,the recorded earthquakes are not coincident with the hot springs in space. It becomes a problem that remains to be solved. However,the uniform distribution may be attributed to the different ways for energy release and the different structural conditions in the different zones. Therefore,the hot springs can not be considered as an indicator for determining the potential seismic sources.

COMPILATION OF HEAT FLOW DATA IN THE CHINA CONTINENTAL AREA (2nd Edition)

Wang Ji-yang, Huang Shao-peng

1990, 12(4):  351-366. 

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During the last 2 years,heat flow data increased significantly in China as a result of implementation of many comprehensive geodynamic (including geothermal) projects and GGT project in China. In this paper,a total of 366 reliable heat flow data is collected from published and in press sources in the Compiilation of Heat Flow Data in the China Continental Area (2nd edition). Statistic analysis of these data shows that the heat flow values in China continental area vary from 20 to 140mWm^-2. The mean value appears to be 66mWm^-2.

HEAT FLOW DATA AND SOME GEOLOGIC-GEOTHERMAL PROBLEMS IN YUNNAN PROVINCE

Wang Ji-an, Xu Qing, Zhang Wen-ren

1990, 12(4):  367-377. 

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More than 20 heat flow data in Yunnan Province have been reported in this paper. Based on the distribution pattern of heat flow and available relevant data,several geologic-heat flow zones are outlined. Moreover,the distribution of temperature and partitioned surface heat flow for the crust in the region is further analysed in combining with data from deep geophysical soundings and the measurements of thermal conductivity and radiogenic heat production of the rock samples. The obtained result verifies the divided geologic-heat flow belts. The high heat flow in most parts of the Yunnan Province,except the southeastern part,can be attributed to the intense geotectonic activity in the region.A large number of active faults and the striking difference in deep geotherms are the prerequisites for the high intensity and high frequency of earthquakes in the region. The intense recent magmatic activity also occurred in the area west of Lujiang River,characterized by the typical geothermal features of plate convergence area.

DISCOVERY OF PALEO-EARTHQUAKE TRACES IN SUQIAN AREA,JIANGSU PROVINCE

Xie Rui-zheng, Ding Zheng, Li Duan-Lu

1990, 12(4):  378-379. 

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BRIEF INVESTIGATION ON THE 1990 EARTHQUAKE IN IRAN

Zheng Jian-dong

1990, 12(4):  380-381. 

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