Table of Content

02 June 1987, Volume 9 Issue 2

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Brief Report

TWO DIMENSIONAL FINITE ELEMENT-BOUNDARY ELEMENT COUPLING MODEL OF MAGNETOTELLURIC SOUNDING

Luo Huan-yen, Zhang Shu-xia

1987, 9(2):  1-16. 

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This paper describes how to apply the boundary element method to solve 2-D magneto-telluric sounding problem and then couple the BEM with finite element method to deal with inhomogeneous geological structure and its relation to regional stress regime. The BEM is able to calculate precisely the derivative of field variables. Such a new approach can more flexibly than others set up the upper boundary condition of the air region. Two practical examples are given. One is the study of topographical effect on the MT fields using boundary element method. There is an inverse relationship between the change of apparent resistivity and the topographical variation. The other is a coupled model of a basin in Nei Monngol Autonomous Region. A lower resistivity zone must exist in the crust and should be thicker below the central portion of the basin. This seems to agree with the regional stress regime changed from extension in Mesozoic to compression in Cenozoic.

QUANTITATIVE REALTIONSHIP BETWEEN THE SOURCE PARAMETERS AND THE EARTHQUAKE MAGNITUDES

Ye Wen-hua

1987, 9(2):  17-25. 

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The physical significance of earthquake magnitudes must be considered when studing the quantitative relationship between the source parameters and earthquake magnitudes. In this paper, a set of stable, uniform functional relations of the source fracture parameters to magnitudes M_L and M_s have been obtained by using the data of 151 smaller earthquakes (1.5≤M_L≤3.9) preceding and following Hai Cheng and Tangshan earthquakes as well as 58 moderate and strong shallow earthquakes(4.4≤M_s≤8.2) on the earth. The relation between the magnitudes M_L, M_s and m_b is discussed as well.The alternative relationship between the source fracture parametes and earthquake magnitudes shows no proportional one-to-one correspondence between the source fracture size of earthquake (i. e fault length, fault area or dislocation etc.) and surface wave magnitude M_s and local magnitude M_L.

THE PRELIMINARY PALEOMAGNEYIC RESULYS OF THE LOWER ORDOVICIAN FROM THE NORTH QILIAN MTS. TERRANCE

Li Yian-ping, Michael McWiuiams, Tan Zheng-zhe

1987, 9(2):  26-26. 

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RHYTHMIC CHARACTERISTICS OF HIGH SEISMIC ACTIVITY IN CHINA MAINLAND

Zhang Guo-min

1987, 9(2):  27-37. 

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This paper discusses the rhythmic characteristics of high seismic activity by using the China Mainland data on M≥7 earthquakes. It is pointed that there is a developmental process, high tide of strong earthquak activity follows quiet and increase of the strong seismic activity (called quiet transition and strong earthquak episode respectively). The continued time, the frequency and energy of the strong earthquakes of each episode in the seismic cycle are discussed in detail in this paper. In addition, region of distribution of strong earthquakes in each cycle is analysed as well as forming of major activity regions in each high tide of strong seismic activity. These results can be used to study marks of the beginning and end of the high tide of strong earthquakes and to determine the major activity regions of the coming high tide of strong earthquakes to a certain extent. The relation between the strong earthquake episodes in the China continent and the deep earthquakes in the Northeastern part of China is analysed as well.

"THE SEISMOTECTONIC MAP OF CHINA BASED ON INTERPRETATION OF SATELLITE IMAGES" WILL BE PUBLISHED

Yao Gan

1987, 9(2):  38-38. 

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SOME FEATURES OF STRONG EARTHQUAKE ACTIVITY IN SPACE AND TIME VARIATION AND RECENT SEISMICALLY ACTIVE TREND IN NORTH CHINA

Wang Liang-mou

1987, 9(2):  39-47. 

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Using rich history earthquake data, author studied some feature of strong earthquake activity in space and time variation in North China.The most remarkable characteristics of strong earthquake activity shows clearly the heterogeneity in time, which is represented by the active and calm period. On the basis of the heterogeneity of earthquake activity, strong earthquake activity since 1369 year can be divided into two active periods. According to release process of strain energy, each strong earthquake active period can be further divided into four stages of released strain energy.Spatial distribution pattern of strong earthquake activity in two active periods shows obviousl difference. These differences mainly are represented by large change of the pregnant environment and spatial distributive range of the large earthquake (M≥7). It is likely that the large change of the pregnant environment of large earthquake (M≥7) is very responsible for this obvious difference in the event time, total released strain energy, maximum magnitude of two active periods and so on.It is worthy to point out that strong earthquake active process of two active periods is not only very similar but also correlatable, Thus author will be able to judge the trend of strong earthquake activity.Finally author discussed possible reason of strong earthquake active difference of two active periods.

LANDPLAN Ⅲ-A SOUTHEAST ASIAN SYMPOSIUM IN HONG KONG (THE OF GEOIEGY IN NRBAN DEVELOPMENT)

Wang Liang-Mou

1987, 9(2):  47-47. 

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"RARE EVENTS IN GEOLOGY"——SECOND INTERNATIONAL SYMPOSIUM IN BEIJING

Zi Niu

1987, 9(2):  48-48. 

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THE DISTRIBUTION OF EARTHQUAKES AND STRESS STATE IN THE JAPAN SEA AND THE NORTHEAST CHINA

Ning Jie-yuan, Zang Shao-xian

1987, 9(2):  49-61. 

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The distributions of earthquakes in the Japan Sea and the Northeast China were studied using the hypocenters determined by I. S. C. from 1966 to 1981. It is shown that the Benioff zone from the northern Honshu to the Northeast China, which is perpendicular to offshore trench of Japan is continuous, dipping about N85°W with a dip angle of about 29° and a thickness of 20 km, extending down to a depths no more than 560 km. The mechanismsn of earthquakes of M_b≥5.0 in the region between the northern Honshu of Japan and the Northeast China were also studied. It is shown that the stress field in the Northeast China coincides with that in the Japan Sea, suggesting that the stress field is caused by compression of pacific plate. In the Benioff zone the directions of the axes of compressional stress vary with the depth: In the region of depth from 100km to 200km the stress state is not simple; most P axes are coincident with the direction and dip angle of the Benioff zone; a few P axes are in the plane of subduction and some of T axes are close to the direction of subduction; in the region of depth from 200 km to 500 km. the most of P axes are nearly horizontal and perpendicular to the strike direction of the Benioff zone; in the depth below 500 km, the P axes are coincident with dip deriction and dip argle of the Benioff zone.

TH-1 AUTOMATIC CARBIDE SYNTHESIZER HAS PASSED THE TEST

Jiao Wen-qiang, Zhang Jing-wen, Chen Yi-jian, Li Gui-ying

1987, 9(2):  61-61. 

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A PRELIMINARY DISCUSSION ON THE QUATERNARY TRANSGRESSION AND THE NEOTECTONIC MOVEMENT IN THE BEIJING AREA

Huang Xing-gen, Zhao Xi-tao

1987, 9(2):  62-64. 

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THREE DIMENSIONAL NUMERICAL MODELING FOR THE DYNAMICS OF THE CONTINENTAL COLLISION

Gao Xiang-lin, Luo Huan-yan, H.J. Neugebauer

1987, 9(2):  65-73. 

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A three dimensional elasto-plastic model was established to explore the mechanical aspects of the India-Asia continental collision by finite element modeling. The results show that the orientations of the principal stresses and the potential faulting types depend on the loading boundary conditions. The push force of the moving India plate results in stress state of thrust and strike-slip types within the Asia continent. The iso-lines of the equivalent stress are characterized by northwest trending arc-form distribution which is consistent with the tectonic feature of west China. The heterogeneity of the model could rise significiant effects on the patterns of the crustal deformation and the stress distribution. The plastic flow in the lower lithosphere and the asthnosphere could make the stress transmitting in the upper lithosphere reach to a much greater extent. The existence of the harder blocks lead to appearance of the relative highstress gradient. For the India-Asia continental collision, the low-angle underthrustingmodel seems to be more reasonable and acceptable than the horizontal indenting model.

PALEOSEISMOLOGICAL STUDY FOR KAXHE FAULT ZONE, XINJIANG

Feng Xian-yue

1987, 9(2):  74-77. 

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The Kaxhe fault Zone is a huge active fault in North Tianshan Mt. in China, it strikes 280℃ the total length of the fault zone measurers 300 km. Rate of vertical movement of the fault zone has been 38mm/yr. Sinse the Quaternary. Seismicity of the fault zone is very frequent. The 1802 Nilke earthguake of M 8 occurred within the zone which caused deformation of the earth surface 100 km long. Prehistoric earthouakes was also very mobile which occurred at least two in the fault zone. The recurrece intervals of the strong earthquakes within the zone is 2500yr.

DETEET TECHNIQUE OF ELECTROMAGNETIC FEEDBAEK FOR GS-15 GRAVITY METER

Guo Zi-qiang

1987, 9(2):  78-84. 

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GS-15 gravity meter gains a high accuracy in the light of measuring relative change of gravitation through shifting swing bar; the capicity tranducer is used here in measuring the shift.Conventional gravity meter tends to loss the high-frequency component of 0.01 H2 and shows the destorted signals with an open loop in use as well as with a source related filter added to the last stage of the system it; follows that the measuring accuracy can not be improved due to a nonlinear circuit.The author has made a component of feedback circuit for the meter in question and taken a closed loop other than the former one; variation of gravitation is represented by the output of the feedback circuit;the electromagnitic force keeps the swing bar in a entire dynamic process of being balanced with an electric level of zero and thus the capicity balanced bridge of the closed-loop system takes the place of the former one, with a time constant of 2 sec..The improved circuit takes off the nonlinear effect and the recorded solid tide may show its extensive harmonic waves and an additional stable output of zero level which may give various data for the study of crustal defomation. seismic prediction and geophysics.

THE ACTIVE FAULTS IN THE EASTERN OF THE WEIHE BASIN

Hang Heng-yue, He Ming-ling, Li Yong-shan

1987, 9(2):  85-90. 

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The activity of 6 main faults in the eastern Weihe basin are discussed in this paper according to some semi-quantitative information. This paper indicates that the fault is dominated by dip slip along with left-lateral strike slip motion.

3DR NATIONAL SYMPOSIUM ON PALEOMAGNETISM, HELD IN GUANGZHOU

1987, 9(2):  90-90. 

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A LATE CARBONIFEROUS PALEOGEOGRAPHIC RECONSTRUCTION

Lin Jin-lu

1987, 9(2):  91-94. 

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The previous attempt at Carboniferous reconstruction was handicapped by the lack of paleomagnetic results from East and Southeast Asia. The recently available paleomagnetic data from the South China block, the North China block, the Tarim block and the Kunlun terrane have therefore provided an opportunity for a new attempt at Carboniferous paleogeographic reconstruction. The late Carboniferous pole for the South China block is at 21.5癗?224.6癊 with the paleolatitude of Hongzhou being 1S. The late Carboniferous pole for the North China block, interpolated from the Permian and the middle Ordovician poles, is at 43.9癗?354.2癊 with the paleolatitude of Taiyuan being 10N. The late Carboniferous pole for the Tarim block is at 52.2癗?179.5癊 with the paleolatitude of Aksu being 25.8癗. The Carboniferous pole for the Kunlun terrane is at 8.8癗?223.0癊 with the paleolatitude of Golmud being 23.7癝. This reconstruction differs from the previous ones in that the North and South China blocks and the Kunlun terrane stretched in the equatorial central Tethys, being separated from both Laurasia and Gondwana. We still do not have reliable paleomagnetic results from the Lhasa terrane, the Qiangtang terrane and the Indochina block. Nevertheless, the paleontological evidence suggests that the Lhasa terrane was a coherent part of India, and that the Qiangtang terrane and the Indochina block were quite close to the South China block. As the North and South China blocks, the Qiangtang terrane, the Indochina block and the Kunlun terrane are all characterized with the specific Cathaysia flora, this group of blocks and terranes may be called the Cathaysia composite continent. This reconstruction is consistent with the flora distribution pattern of the world in the late Paleozoic, and in general supports the concept of the socalled Cimmerian continent.

PENGLAI EARTHQUAKE OF 1548

1987, 9(2):  95-96. 

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