Table of Content

04 September 1996, Volume 18 Issue 3

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Brief Report

TANGSHAN-HEJIAN-CIXIAN NEWLY-GENERATED SEISMOTECTONIC ZONE

Xu Jie, Niu Luanfang, Wang Chunhua, Han Zhujun

1996, 18(3):  193-198. 

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In the study of seismotectonics,much attention is usually paid to active fault zones which have long evolution history and large scales.However there are also newly-generated seismotectonic zones in the recent tectonic stage.Seismicity has a close relation with both kinds of tectonic zones.It can be seen that Tangshan-Hejlan-Cixian seismic zone is a new crustal shear fracture zone which has been developed since the Neogene as well as a newly-generated seismotectonic zone in North China based on analysis of the data of earthquakes and geological structures.

A STUDY ON THE MECHANICS OF STICK SLIP BY CONTROLLING A LINEAR COMBINATION OF LOAD AND DISPLACEMENT

He Changrong, Zhang Liu

1996, 18(3):  199-211. 

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Two series of triaxial tests were conducted for investigation of the mechanics of stick slip that occurred at high pressure and low temperature conditions.By the negative stiffness testing which cancels out a portion of compliance of the machine-specimen system,shear stress versus slip curves of granite saw cuts and quartzite shear fractures were obtained under 300MPa confining pressure.The duration of the slip was increased to about 0.5 second which would be otherwise several milli second when loaded by conventional test methodThe process was well recorded by an X-Y recorder whose cut off frequency is 2. 5 Hz.By another test which can reduce the intrinsic machine stiffness to a dislred value,stress drop was found to depend on the value of stiffness while slip distance remains comparable under different stiffness settings.This result is completely different from estimates by conventional friction models,say,the rate and state dependent friction model and slip weakening model.However,the result is similar to that when strength is controlled by geometric constraints of the contacting surfaces as noted by Lockner and Byerlee (1990).

CRUSTAL DEFORMATION AS A PRECURSOR TO EARTHQUAKE ON PLATE MARGIN

Xie Jiaomin, Wang Ruobai, Li Yanxin

1996, 18(3):  212-214. 

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DEFORMATION PROPERTY RECOGNITION OF THE CRUST AND UPPER MANTLE

Waug Shengzu

1996, 18(3):  215-224. 

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Based on the Maxwell′ s and Kelvln′ s rheological models,the deformation properties of the different layers in the crust and upper mantle are recongnized using an index called relaxation number,i. e.the ratio of the duration to the relaxation or retardation time.It is indicated that the asthenosphere is always viscous and the deformation properties of the overlying layers are as follows: the mantle lid, the lower crust,and,even, some of the upper crust are viscous in the long geological processes; the upper crust and mantle lid are elastic in the duration of a few decades; and, in general, the upper crust is elastic,while the lower crust and mantle lid are vis cons or anelastic/elasto-viscous in the duration as long as that between the above two situations.In addition, the problems of the flow in the mantle lid, the intraplate long-range transmis sion of driving force, etc. are discussed in terms of the recognition of the deformating properties.

DISCUSSION ON COEFFICIENTS OF STATISTICAL REGRESSIONS BETWEEN MAGNITUDE AND EARTHQUAKE RUPTURE PARAMETERS

Liu Jing, Wang Liangmou

1996, 18(3):  225-236. 

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Based on the collection of six kinds of empirical relationships between magnitude and rupture parameters, the ranges of coefficients a_i and b_i(i=1,2,3,4,5,6) and their relationships are analyzed systematically.It is found that a_i and b_i are of more or less negative correlation, and the coefficients of different types have stable ranges while the stability and convergence degree are different.It suggests that more rupture parameters are involved in statistical relations, the coefficients are more stable.In the end, theoretical expression of a_i and b_i are derived from dislocation model of fault to explain the relationships between a_i and b_i and ranges of value of some parameters are presented as well.

STUDY ON THE QINGHAI-XIZANG CRUST AND ITS MOVEMENTS VIA THE TEMPORAL AND SPATIAL GRAVITY DISTRIBUTION

Zhang Chijun

1996, 18(3):  237-244. 

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In this paper,we give a general introduction to our recent studies on the gravity field of the Qinghai-Xizang region. Our research works are composed of the three main parts: based on the isostasy principle and the thermal colomn model, we cornputated the undulation of the Moho in terface and the density anomaly of the upper mantle,and assessed the rise of the Himalaya mountain and the corresponding mechanism. Accoording to the residual geoid distribution and the ideal heating convection model, we discussed the force source of the movements of Qinghai-Xizang region and central China.Based on the repeated gravity observations, it is able to detect the rise of the Qinghai-Xizang plateau and the activity of the fault.

JUDGE OF POTENTIAL FOCAL AREAS FOR STRONG EARTHQUAKES IN EASTHERN YUNNAN AND RESEARCHS ON THEIR TECTONIC MARKS

Han Xinmin, Yu Weixian

1996, 18(3):  245-249. 

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Ten or more ideal characteristic marks which are relatively correled to latent focal areas of strong earthquakes have been determined by the sieving method of comprehensive pattern recognition for 17 selected tectonic marks of selsmogeology, geophysics and crustal deformation in eastern Yunnan. And the potential focal areas of strong earthquakes in this region have been evaluated according to the 10 marks. Finally, the seismotectonic idexes of potential focal areas for strong earthquakes have been analysed as well.

SYNCHRONOUS ANORMALIES OF INTERMENIATE-SHORT TERM OF MULTI-WELL AND MULTI-ITEM OF UNDERGROUND FLUID IN BEIJING REGION BEFORE THE EARTHQUAKE,BAOTOU WEST,M_s6.4

Che Yongtai, Zhang Peiren, Zhu Qingzhong

1996, 18(3):  250-250. 

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TECTONIC EXPLANATION OF THE MAP OF EPICENTRE DISTRIBUTION IN JIANGSU REGION

Tian Jianming, Xie Huazhang

1996, 18(3):  251-257. 

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A map of epicentre distribution contains a lot of tectonic information about the upper-middle crust.It is a menifestation of currently active tectonics on the surface of the Earth. According to the method of visual seismic line advanced by Prof.Ma Zongjin,a tectonic explanation of the image of earthquake epicinters with M_L≥2 during 1970～1992 years as well as with M_s≥4. 7 during 1500～1969 years in Jiangsu region is made in this paper. The main conclusions are as follows:(1)There mainly exist four groups of seismic line with different direction, that is NE,NW, NNE and EW in this region. The first two gropos of seismic line are rather obvious and form a grid-like structure at equal distance span. Most moderate and strong earthquakes that cocurred in this region are located in the intersections of the two groups of seismic line.(2) There are more dense and complex seismic lines in the depression of southern Yellow Sea. It seems that the depression of southern Yellow Sea is an independent tectonic unit of higher frequency and in tensity of earthquake activity.

RESULT OF INTERMEDIATE-LONG-TERM PREDICTION OF BAOTOU M_s6.4 EATHQUAKE BY USE OF INDICATION OF FAULT MOVEMENT ON SATELLITE IMAGES

Li Jianhua

1996, 18(3):  258-258. 

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EXPERIMENT STUDY ABOUT ELASTIC WAVE VELOCITIES IN ROCKS UNDER DIFFERENT PRESSURE AND TEMPERATURE

Ma Ri, Lu Minjie, Yang Xiaodong

1996, 18(3):  259-265. 

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During study on Manzhouli-Suifenhe Global Geoscience Transect(GGT), P.R.China,the authors have done a series of experiments about elastic wave velocities in rocks under various pressure and temperature. The results show that:(1) the composition of rock is a major role in transimitting elastic wave velocity in rocks, for example, the velocity tends. to increase from the acid rock to the basic ;(2) Elastic wave velocities in rocks vary with the pressure and temperature, usually increasing with the increase of pressure and temperature.

DISTRIBUTION OF SEISMIC INTENSITY OF M6 DOUBLE EARTHQUAKES IN BEIBUWAN GULF

Wei Bolin

1996, 18(3):  266-268. 

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PRELIMINARY STUDY ON THE CHARACTERS OF THE SPECTRUM OF HIGH FREQUENCY WAVES IN THE ROCK

Ma Wentao, Ma Jin, Liu Liqiang, Lei Xingli

1996, 18(3):  269-276. 

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In this paper we have studied the characters of the spectrum of high-frequency AE waves in rock containing a single long fault. The distribution of arrival time of waves,the intensive translation of phases and amplitude of waves changed,which depends on the position of source and accepting points,and the direction of fault.Specially,the amplitudes of waves were reduced largestly when propagating through the fault in larger angle.Therefore,the wave propagation in the medium depends on the geological constructure of the medium.

VARIATION CHARACTERISTICS OF ELASTIC WAVE DURING THE FRACTURE-PREPARING PROCESS OF GNEISS UNDER TRUE TRIAXIAT COMPRESSION

Zhao Jinming, Hu Yili, Wang Bin, Xu Zhaoyong

1996, 18(3):  277-281. 

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During the preparing process from compression to fracture,the elastic waves of gneiss have obvious various characteristics along the σ3 direction( obliquely crossing with main fracture plane): the various state of the first arrival time of P,S wave shows a shape of relatively high value～stability～high value～decrement,and the ratio of trave time has shape of stabiltity～low value～increment. The amplitude of P,S waves shows a shape of low value～stability high value decrement(low value) and their ratios have a shape of relatively stabllty～very high value～decrement. The variation state of attenuation coefficient of the wave trian shows a shape of stability～low value～increment.The main reason for those variations is the openingand closing of micro-cracks,the nonsynchronous variation of P, S wave and the difference of their variations.

THE ANOMALY OF THE WATER-MERCURY OF SHILIQUAN WELL BEFORE CHANGSHAN EARTHQUAKE,M_s5.2

Ma Zhifeng, Li Liubo

1996, 18(3):  282-283. 

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LINEARITY ANALYSIS OF ACOUSTIC EMISSION WAVEFORMS BEFORE AND AFTER THE DEFORMATION AND FAILURE OF DISCONTINUOUS ROCKS

Wu Guoyou, Feng Deyi, Zeng Zhengwen, Ma Jin

1996, 18(3):  284-288. 

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In order to investigate the possibility of temporal linearity(r) and spatial linearity(a)of natural earthquake waveforms serving as earthquake precoursory index, acoustic emission wave forms recorded before and after the deformation and failure of single-joint discontinuous rocks were analysed with the method of temporal and spatial linearity. The results show that the temporal linearity(r) decreases after the failure of discontinuous rockmass specimens with different joint-angles. In all cases the spatial linearity(a) also decrease,with even larger magnitude. Before the occurrence of the largest acoustic emission event(corresponding to the failure), r and a show decreasing-type anomalous variations in the studied cases.