Table of Content

09 June 1999, Volume 21 Issue 2

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Brief Report

RESTLUS OF GPS SURVEYS FOR CRUSTAL DEFORMATION IN NORTH CHINA AND THEIR IMPLICATIONS TO EARTHQUAKE GEOLOGY

Gu Guohua, Wang Ruobai, Sun Huijuan, Sun Hanrong, Yang Chunhua

1999, 21(2):  97-104. 

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This paper briefly introduces the GPS (Global Positioning System)field surveys for crustal deformation in North China in 1995 and 1996,the processing of the observation data with the Bernese software,results of the horizontal displacements,strain and the vertical displacements The implications of the tectonic movement are analysed seismogeologically and it is suggested that the horizontal crustal deformation observed by GPS may reveal some information of activities of upper crust blocks

THE LATEST ACTIVITIES OF FAULTS IN THE TAI'AN REGION,SHANDONG PROVINCE AND THE TAISHAN MOUNTAIN EARTHQUAKE

Chao Hongtai, Wang Zhicai, Li Jialing, Cui Zhaowen

1999, 21(2):  105-114. 

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Based on explaining satellite pictures,five main faults in the Tai'an region,Shandong Province have been investigated According to age research,it is found that the piedmont fault of Taishan is a late Pleistoncene active fault with the latest active age of (1.42±12)×10⁴a B.P. The seismogenic structure of the Taishan earthquake occurred in 1831 B.C. is discussed It is suggested that this earthquake may be related to the activities of the piedmont fault of Taishan and may be a medium earthquake (M ≤6.5) without surface ruptures

THE SEISMOGENIC STRUCTURE OF THE 1995 CANGSHAN M_S5.2 EARTHQUAKE, SHANDONG PROVINCE

Wang Zhicai, Chao Hongtai

1999, 21(2):  115-120. 

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By detailed field geological survey, combining with analyses of the basic parameters, focal mechanism solution, the characteristics of the earthquake sequence and macroseismic damage investigation of the 1995 Cangshan M_S5.2 earthquake, we propose that the seismogenic structure of the event is the Wanjiazhuang fault The magnitude of this event does correspond with the scale and activity of the fault and the seismotectonic background

THE FOCAL FAULTS OF HISTORICAL GREAT EARTHQUAKES INFERRED BASED ON CURRENT SMALL SHOCKS TAKING AN EXAMPLE OF 1830 CIXINA, HEBEI, M 7(1/2) EARTHQUAKE

Diao Guiling, Zhang Sichang, Zhao Jun, Wang Zhaojun, Wang Junguo

1999, 21(2):  121-126. 

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The 1830 Cixian, Hebei province, M 7(1/2) earthquake is a strong sequence with high activity and long duration In recent years, a large amount of small shocks have been recorded in the region of Cixian county by the Handan remote sensing seismological network The 3 dimensional spatial distribution of focuses and focal mechanism of these small shocks are analyzed It is suggested that the focal fault of the 1830 Cixain earthquake is a fault with NWW strike and left lateral strike slip This result is in agreement with the isoseismal and surface rupture belt of the Cixain earthquake Therefore, it is feasible to outline spatial orientation and motion mode of the focal fault of historical great earthquakes from characteristics of swarms of current small shocks which occurred in the historical seismic region by combining method of seismology and geology

ACTIVITY WAYS AND FORMATION AGE OF THE NNW TECTONICS IN THE NORTHERN TIBET PLATEAU

Hou Kangming, Shi Yamiu, Zhang Xing

1999, 21(2):  127-136. 

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Based on the recent field work,we analyze the geological geomorphic characteristics,activity ways and formation ages of the NNW tectonics developed in the northern Tibet plateau The results indicate that this NNW tectonics exists in all the area from north to the east of Kunlun moutain to the Hexi corridor In geomorphology it represents the structural configuration of uplift downsink jaxuposition from east to west The NNW faults developed in the east margin of the uplift zone as fold companion thrust compression zone The downsink zones are composed of a series of depressive basins located between middle and late Quaternary,highly active which not only control the formation and development of the geomorphic feathers but also play vital roles to seismic activity and orogeny and occurrence of strong events The NNW tectonics began to develop from the late Tertiary to early Quaternary and uplift of large scales happened from middle Pleistocene

COMPARING TWO TYPES OF RATE AND STATE DEPENDENT FRICTION LAWS

He Changrong

1999, 21(2):  137-146. 

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This work compares the slowness friction law with the Ruina Dieterich friction law under both constant normal stress and variable normal stress conditions Dynamic motion with the slowness friction law in a single degree of freedom system is analyzed numerically and compared with the other By examining the property of the equations,it can be seen that the two constitutive laws converge to each other during motions around a certain steady state This is also implied by the consent in linear stability analyses for both cases as shown in previous studies Under constant normal stress condition,the two constitutive laws differs in many aspects:(a) Stress displacement curve in stick slip with the slowness friction law is different from the Ruina Dieterich friction law in that the stress change during acceleration and deceleration are strongly not symmetric;(b) In the deceleration phase,the slowness law has a roughly constant stress segment in which the logarithm of state and logarithm of velocity are linearly coupled,and most portion of the state value recovers during this segment;(c) With slowness friction law,dynamic stress drop scales with both b a and stiffness; (d) The minimum velocity in the deceleration phase with the slowness law is less than the Ruina Dieterich law by 10 orders of magnitude Under variable normal stress condition,the phase plane plot with the slowness law is similar to the constant normal stress case except the non appearance of constant state line whereas that of Ruina Dieterich law has a long tail in the deceleration phase in which little hysteresis occurs

CHARACTERS OF WAVE VELOCITY AND CONSTITUTION STRUCTURE OF ROCKS OF THE CRATON CRUST IN NORTH PART OF NORTH CHINA

Zhang Younan, Sun Junxiu

1999, 21(2):  147-155. 

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Compressive wave velocities of metamorphic rocks from the Archaean group in the north part of North China have been measured under high pressure and high temperature By the fitting method,these rocks are divided into velocity grades representing acidity and basicity of them With combination of these results with the geological and seismic sounding data we propose the model of the crust The constitution of upper crust in the current period is "craton rock suite" which consists of TTG metamorphic rocks+khondalite series+granit+minor metabasic rocks and garnet basic rocks The lower crust has three parts of materials "craton rock suite" composition; basic and ultrabasic materials from mantle in post Archaeozoic era; residual basic materials through partial melting of country rock "craton suite" while mantle magma intruded Development of both the latter basified the lower crust with primary "craton rock suite" composition The constitution of the middle crust is "craton rock suite" materials and basic materials of mantle source

DRAWING COMPREHENSIVE ISOSEISMAL LINES USEING THE TOPOLOGICAL OVERLAY PRINCIPLE OF GIS

Qu Chunyan, Ye Hong

1999, 21(2):  156-158. 

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The comprehensive isoseismal lines of southeast coastal region of China are drawn by using the topological overlay principle of GIS The related program for this method is also made It provides a convenient tool for seismic zonation of engineering earthquake research

ELECTRIC STRUCTURE OF THE CRUST OF THE MANAS EARTHQUAKE AREA IN XINJINAG AUTONOMOUS REGION

Zhan Yan, Zhao Guoze, Tang Ji, Zhao Junmeng, Jin Guangwen, Deng Qianhui, Wang Jijun

1999, 21(2):  159-167. 

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Magnetotelluric data have recently been obtained at 35 sites along a profile of about 93km long and orientated approximately N-S in the Manas earthquake area which lies in northern Tianshan mountains of Xinjiang Autonomous region From these data the apparent resistivities,impedance phases,skewnesses,optimal rotation angles and induction vectors were calculated and analysed The 2-D inversion method RRI was used for the data interpretation The results show that the shallow crust can be divided into 5 sections and the deeper crust into 3 sections according the electric structure The boundaries of different sections are coincidence with faults The maximum sediment basement is about 12 km deep The resistivity distribution near the Manas earthquake focal area is significantly heterogeneous

THE COMPARISON OF LUMINESCENTE PALEODOSES OF DIFFERENT SEDIMENTS

Yin Gongming, Zhao Hua, Lu Yanchou, Chen Jie, Shen Jun

1999, 21(2):  168-170. 

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Seven samples of wind blow,glaciofluvial and fluvial sediments are collected from northern Tianshan Mountain Each sample is dated for fine grain using the the luminescence techinque to get three paleodose of TL,GLSL and IRSL Comparison of the paleodoses shows that they are in agreement for win blow samples,but different for the the samples that were not totally bleached before sedimented The paleodose of TL is larger than those of GLSl,IRSL

INVERSION OF THE PRESENT KINEMATIC CHARACTERISTICS OF THE ALIUN FAULT ZONE FROM SEISMIC MOMENT TENSOR

Wang Weidong, Li Shaorui

1999, 21(2):  171-175. 

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We present the theory and method for inversing the kinematics parameters of a fault zone and then use this method to study the present kinematic characteristics of the Altun fault zone The results show that the Altun fault zone is generally compressive in the direction of S14癊,its compressive rate is 1.13 mm/a,and the rate of its left lateral shear movement is 0.17mm/a

RECONSTRUCTION OF U-SERIES LABORATORY OF INSTITUTE OF GEOLOGY,CHINA SEISMOLOGICAL BUREAU AND DATING OF THE QUATERNARY STANDARD SAMPLES

Chen Wenji, Hu Yutai, Wang Fei, Zhang Zhonglu

1999, 21(2):  176-177. 

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NEW EVIDENCE AND ANALYSES FOR THE NWW TRENDING CHANGPING FENGNAN FAULT

Li Jianhua, Hao Shujian, Hu Yutai

1999, 21(2):  178-184. 

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The NWW trending Changping Fengnan fault is a hidden active fault found by interpretating satellite photograph It is the largest one in the NWW trending Zhangjiakou Penglai fault zone During Quaternary this fault behaved as a left lateral strike slip and normal fault Deep seismic sounding indicates that this fault extends to the top of the upper mantle

AN EARLY CRETACEOUS PULL APART BASIN IN THE MIDDLE SECTION OF THE TAN LU FAULT ZONE

Zhou Jianbo, Takao Miyata, Wang Zeli

1999, 21(2):  185-192. 

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The Shichang Zhonglou basin is situated in the Yihe Shuhe area at the middle section of the Tan Lu fault zone The strike slip Tan Lu fault cuts the Qinling Dabie Jiaonan orogen of Pre Mesozoic,while in the study area the Yihe Shuhe (Yi-Shu) fault overlies the north margin shear zone of the Jiaonan orogen,which gives out an ⁴⁰Ar/³⁹Ar age of 136.2 Ma The faults are unconformably covered with the Qingshan Group of the age of 119 Ma (K-Ar whole rock) These evidence show that the Tan Lu fault had significant strike slip movement The Shichang Zhonglou basin is controlled by the Yihe Shuhe fault,it occurs as a rhombachasm tectonic basin with a length 60 km and a width 30 km The thickness of the Early Cretaceous Laiyang Group in the basin is more than 6263.7m The sedimentation rate is greater than 0.4mm/a The fast changing sedimentary facies in the Laiyang Group reflects that the basin was narrow and deep Migration of the sedimentation center is consistent with the strike slip boundary faults showing the characteristics of "depositing while strike slip moving" It is suggested that the Shichang Zhonglou basin is a pull apart basin formed during the process of sinistrial strike slip movement of the Tan Lu fault zone in early Cretaceous