Table of Content

09 December 1992, Volume 14 Issue 4

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Brief Report

DEFORMATION FEATURES OF MANTLE XENOLITHS ALONG TANLU FAULT ZONE AND THEIR GEOLOGICAL IMPLICATIONS

Lin Chuanyong, Shi Lanbin, J.V. Ross, J.K. Russell

1992, 14(4):  289-304. 

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The mantle xenoliths from 6 localities along and eastward of the active Tanlu fault zone are mostly spinel lherzolite, with few exception of wehrlite. The textures are variable from initial porphyroclastic through granuloblaslic to mylonitic. The analysis of mineral equilibria has revealed that these xenoliths attained to a good state of equilibrium.The equilibrium temperatures determined by using 3 different methods are 700-1000℃, while the pressures have been estimated to be in a range of 0.9-2.5 GPa. The constructed geotherms have shown that most of the points lie above the theorectical continental geotherm, indicating the existence of an upper mantle diapir associated with tectonic extension known to occur in thus region. The low temperature of mylonitic xenoliths indicates the existence of an active shear zone just below the crust. It might control the development of seismically active zone in this region.

《ENGLISH-CHINESE DICTIONARY OF REMOTE SENSING GEOLOGY》 HAS BEEN PUBLISHED

1992, 14(4):  304-304. 

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STUDY ON STRONG EARTHQUAKE ACTIVITY AND RISK AREAS IN THE SHANXI GRABEN SYSTEM

Xu Xiwei, Deng Qidong, Dong Ruishu, Zhang Chongli, Gao Weian

1992, 14(4):  305-316. 

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Shanxi graben system is one of the most famous strong earthquake belts on China Continent. In this paper, the problems on recurrence and migration of the historic strong earthquakes (M≥6), the precusory anomalies of the intermediate and strong earthquakes (41/3≤M<7) before M≥7 earthquakes occurring, and linear segmentation of the strain accumulation curves are discussed. The temporary trends of the recent and future seismicities are analysed. Finally the possible seismic risk areas in which intermediate and strong earthquake may occur are also outlined in the graben system.

RESEARCH ON THE RECENT SURFICIAL FAULTING ON THE NORTHERN SEGMENT OF THE ANNINGHE FAULT ZONE AND EARTHQUAKE POTENTIAL

Qian Hong, Tang Rongchang, Wen Dehua, Huang Zuzhi

1992, 14(4):  317-323. 

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Basing on the charateristics of recent surficial faulting, discontinuity of the faults, slip rates and prehistorical earthquakes, we discuss the earthquake potential on the northern segment of the Anninghe fault zone in this paper. We believe that the discontinuous fault segments have become the units of seismic ruptures by individual events, and hence provide the earthquake potential. Among the segments the northern segment near Yejidong has the highest seismic potential and the magnitude about 7. We also believe that this segment has high seismic hazard because the time clapsed since the last event has reached an average recurrence interval of prehistorical earthquakes.

A SEMINAR ON THE ROLE OF WOMEN-GEOLOGISTS HELD IN BEIJING

Yao Yanzhi

1992, 14(4):  323-323. 

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SEAWATER INJECTION INTO SUBDUCTION ZONE:AN ASSUMPTION ON INDUCING GENESIS OF SHALLOW EARTHQUAKES

Liu Monghua

1992, 14(4):  324-324. 

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A TECTONOPHYSICAL METHOD FOR ESTIMATING SEISMIC ENERGY AND EFFICIENCY

Wang Shengzu

1992, 14(4):  325-332. 

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A tectonophysical method for estimating seismic energy and efficiency from the data on tectonic features, geological media, physical environment and driving background is established on the basis of a simplified elliptical hypocenter model, which considers strong constraint from hypocentral surroundings and uniformization of sliding resistance, and the calculation of hypocentral parameters. The method is examined by means of calculations of data of 28 strong earthquakes with magnitudes greater than 6.0. The results show that the seismic efficiencies, η, ranges from 0.008 to 0.050 and deviation of the estimated magnitudes from those determined previously by conventional seismological methods is within ±0.5 for 78.6% of the earthquakes examined.

2ND INTERNATIONAL COFERENCE ON CONTINENTAL EARTHQUAKES HELD IN BEIJING

Xiao Shan

1992, 14(4):  332-332. 

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DISCUSSION ON PRINCIPLES AND METHODS FOR DELINEATION OF LARGE HISTORIC EARTHQUAKE AREAS WITH HIGH SEISMIC EFFECTS

Qing Baoyan, Chen Jiachao, Feng Xiaying

1992, 14(4):  333-340. 

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A further discussion is made on the method for delineation of focal areas of large historic earthquakes from data of recent small earthquake activity and from genetical viewpoint on the principles and methods for the delineation and some quantitative criteria. A few earthquake examples are also cited in this paper for analysing and checking the effectiveness of the methods.

EFFECT OF FRICTIONAL SLIDING ON THERMOLUMINESCENT PROPERTY OF QUARTZ AND CALCITE AND ITS SEISMOGEOLOGICAL SIGNIFICANCE

Ma Shengli, Ji Fengju, Ma Jin, Liu Tianchang, Xu Xiuqin

1992, 14(4):  341-349. 

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The curves showing the change of residual thermoluminescent density of quartz and calcite with temperature at confining pressures of 100 MPa and 30 MPa, respectively, are established from the results of experiments under high temperature and pressure. According to the curves, the effect of frictional sliding under the corresponding confining pressures and at different sliding rates on residual thermoluminescent density of quartz and calcite and related temperature change are studied by means of triaxial frictional experiments and thermoluminescent measurements. Based on the result and the existing theory, the applicability of thermoluminescent method to dating the faulting and to determining the sliding mode along the fault is discussed.

CELEBRATION OF 70 ANNIVERSARY OF GEOLOGICAL SOCILTY OF CHINA

1992, 14(4):  350-350. 

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CONGRATULATION ON FOURTY ANNIVERSARY OF CHINA UNIVERSITY OF GEOSCIENCES

1992, 14(4):  350-350. 

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STUDY ON THE PROTEROZOIC DYKE SWARM IN NORTH CHINA

Chen Xiaode, Shi Lanbin, Jia Sanfa

1992, 14(4):  351-357. 

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The rocks of dyke swarm in North China have commonly diabasic texture. Their composition is of tholeiite with low Mg and high K and Na. The swarm consists of three subswarms, which were formed 1500Ma, 1200Ma and 900 Ma ago, respectively.The relevant extensive stress field in three phases is suggested and their directions are NS, NE-SW and SE-NW.

EARLY PRECAMBRIAN AMPHIBOLITE AND GREENSCHIST FACIES AND LAYERING OF MIDDLE-UPPER CRUST IN EAST HEBEI

Wu Zongxu

1992, 14(4):  358-360. 

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A DISCUSSION ON ⁴⁰Ar-³⁹Ar AGE SPECTRA OF THREE KINDS OF WHOLE ROCKS

Li Daming, Chen Wenji, Li Qi, Wang Xin

1992, 14(4):  361-367. 

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Some problems emerging during analysis of basalt, diabase and clay minerals from fault gouge using ⁴⁰Ar-³⁹Ar method are discussed. Difference between ⁴⁰Ar-³⁹Ar total gas age and K-Ar age can be explained by inhomogeneous loss of Ar from different minerals during fast neutron irradiation. ⁴⁰Ar-³⁹Ar age spectra of three diabase samples from diabase viens indicate intrusive ages of the veins and show that despersion of K-Ar age values in the same area could be caused by effect of later geologic events. For clay mineral samples from fault gouge, ³⁹Ar recoil loss during fast neutron irradiation could increase ⁴⁰Ar-³⁹Ar total gas ages of <1μm grain-size fraction. Lower step ages at lower temperature in ⁴⁰Ar-³⁹Ar age spectra of <1μm and 2-10μm grain-size fractions may be a result of stronger late movement alone the fault.

FIRST DISCOVERY OF EYEBROW RIDGE ZONE IN SOUTH CHINA

Pan Jianxiong, Zhang Yuyou, Long Yunwu

1992, 14(4):  368-368. 

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STUDY ON THE ABRUPT CHANGE OF PRECURSORY ANOMALIES PRIOR TO TANGSHAN EARTHQUAKE

Qiu Zehua, Zhang Baohong

1992, 14(4):  369-373. 

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Observations suggest that at the beginning of May, 1976, the crustal media in the Tangshan M=7.8 earthquake epicentral area has undergone some important event which caused abrupt changes in anomalies such as ground deformation, water level, gravity, electrical restivity, etc. From the viewpoint of tectonic collapse, all these anomalies can be related to the occurrence of tensile fractures close to the surface.Since this type of tensile fractures was caused by local uplift on the main fault, they extended parallel to it. Continuous observation data of stress field strongly support this inference.

DISCOVERY AND SIGNIFICANCE OF BURIED ACTIVE FAULTS IN THE M1NGGUANG AREA,ANHUI PROVINCE

Yao Daquan

1992, 14(4):  374-375. 

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MICRO-DEFORMETION AND MECHANICAL PROPERTIES OF MONTMORILLONITE AT HIGH TEMPERATURE AND PRESSURE

Feng Jinjiang, Li Jianguo

1992, 14(4):  376-380. 

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This paper deals with the characteristics and mechanism of micro-deformetion of montmorillonite, especially the relationship between deformation and increasing temperature and pressure. The study shows that micro-deformation of montmorillonite increases with increasing temperature at the confining pressure of 200MPa. The differential stress decreases with increasing temperature (100-300℃) at the same strain but increases at temperature 500℃. The deformation modulus and yield strength increase at T≤500℃ and σ₃≤300MPa due to dewatering of montmorillonite with increasing temperature. The gradual failure of montmorillonite took place at high temperature and pressure. It is favorable to stable slide.