Table of Content

08 December 1999, Volume 21 Issue 4

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Brief Report

ACTIVE CHARACTERS OF THE YINGKOU WEIFANG FAULT ZONE IN THE CENOZOIC ERA

Xu Jie, Song Changqing, Gao Zhanwu

1999, 21(4):  289-300. 

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The Yingkou-Weifang fault zone, which is practically one part of Tanlu fault zone in Liaohe-Bohai, lies in the east edge of Bohai Gulf Cenozoic rift basin. It can be divided into two parts, the northern and southern part, by the Beijing-Penglai fault zone. The northern part consists of two faults which interweave like a braid each other. The southern part consists of two parallel faults, and is cut into four parts by Huangbei, Laibei, and Weibei NEE trending fault. The horizontal stretch and vertical movement of the northern part of the fault zone are strong in the Paleogene period, controlls the rifting basin development; nevertheless the right-lateral slip has been prominent since the late Oligocene. The activity of the southern part is weak in the Cenozoic Era, but the cross faults have evident horizontal stretch and vertical action. In the Cenozoic Era, the activity of the fault zone migrated to the middle part from the northern and southern part, and the activity of northern part probably also had the trend from west to east. A NE trending seismic zone, which obliquely cross the Yingkou-Weifang fault zone in the middle of Bohai, is probably the extending part of the Huangheko Liaocheng newly generated seismotectonic zone towards the sea.

ROCK VARNISH MICROLAMINATIONS FROM THE NORTHERN TIAN SHAN,XINJIANG AND THEIR CHRONOLOGICAL IMPLICATIONS

Zhou Bengang, Liu Tanzhuo, Zhang Yuming

1999, 21(4):  301-308. 

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We collected 100 rock varnish samples from the northern Tian Shan for ultra-thin sectioning. Laterally continuous dark and orange microlaminations are observed in these ultra-thin sections of rock varnish. Microprobe chemical analyses indicate that dark layers in the varnish are rich in Mn and orange layers are poor in Mn. Microscopic examinations of varnish ultra-thin sections reveal a lamination pattern that is regionally consistent and comparable. Based on paleoclimatic and geomorphic age control,the Late Pleistocene varnish lamination sequence is tentatively established and its chronological impications are explored as well.

ON IDENTIFYING THE FORMATION MECHANISM OF SURFACE SCARPS IN PINGGU AREA OF BEIJING

Jiang Wali

1999, 21(4):  309-315. 

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Based on observation and comparison to the surface scarps of the Pinggu-Sanhe area, the mirco-geomorphy differences between the river erosion scarp and fault scarp are studied. Direction of scarps caused by river erosion follows the river, is unstable and the tendency of scarps is symmetric along the river. While distribution of fault scarps is not influenced by the river direction. If the fault is dominated by normal slip, motion direction of both sides of scarps is stable. Study results indicate that the surface scarps of the Pinggu area are river erosion scarps. Characters of river erosion sediment and fault dislocation sediment are analysed from structural geomorphy and stratigrapic sedimentography. It is suggested that there are two possible interpretations for the data of shallow seismic exploration and boring in the Pinggu area.

RECURRENCE BEHAVIOR OF LARGE EARTHQUAKES AND HOW TO TAKE AVERAGE RECURRENCE INTERVAL OF LARGE EARTHQUAKES

Ran Yongkang, Deng Qidong

1999, 21(4):  316-323. 

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A detailed study of paleoearthquakes in Yanhuai basin and along Haiyuan fault of China shows that recurrence behavior of large earthquakes is of variery. Characteristic earthquake is common behavior of fault activity and there is grading of characteristic earthquakes. Besides, there is phasing of recurrence behavior of large earthquakes and the interaction between segments and (or) faults. These must influence the recurrence behavior of large earthquakes. Then, when the phasing of recurrence behavior appears and when the characteristic earthquakes of different intensity cause different interval time of recurrence, we must take trend average value of recurrence interval for assessing hazard of large earthquakes using either definite method or probability method. For example, the different average value is taken as fault behavior is during long-interval between event clusters and as it is during short-interval in a cluster. Characteristic earthquakes occurred on a master segment have different average value of recurrence interval from those occurred on a secondary segment so the different average value should be taken.

STRUCTURAL BELTS AND DEFORMATION FEATURES OF THE JUNGGAR BASIN

Wang Weifeng, Wang Yi, Lu Shikuo, Ma Zongjin

1999, 21(4):  324-333. 

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The Junggar basin is a large-scale compound basin filled with the Paleozoic, Mesozoic and Cenozoic continental deposits. The structural features are very complicated because of the effects of tectonic movements during late Variscan, Indosinian, Yanshan and Himalayan movements. The basin can be divided into six structural belts according to structural styles of the basin. There are two "fish scale shape" thrust-nappe structures in northwest part of the basin. The echelon thrust-nappes formed in northeast part. There are a series of parallel thrust faults in west and east parts. There are the oblique-imbricated structure and the imbricated structure in south part. Uplifts, depressions, thrust faults, and normal faults formed before Jurassic in the central part of the basin.

MICROSTRUCTURAL INDICATORS OF STRUCTURAL DEFORMATION CONDITIONS IN THE SHANGDAN MYLONITE ZONE OF QINLING BELT.

Zhou Jianxun

1999, 21(4):  334-340. 

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Microstructures of quartz and feldspars and quartz fabrics from the Shangdan mylonite zone indicate that from west to east in this zone the structural deformation conditions change from low- greenschist facies to middle- to high- greenschist facies, then become high- greenschist to low- amphibolite facies. Under the deformation condition of low- greenschist facies, quartz is dominated by type Ⅰ quartz ribbons and feldspars are mainly of brittle cracking characteristics. Quartz c- fabrics is of single girdle pattern under this condition. Under the deformation condition of middle- to high- greenschist facies, quartz is dominated by type Ⅱ quartz ribbons. Plagioclase is mostly in the state of brittle cracking flow, but K- feldspar begins to transform to ductile state. Quartz c- fabrics show Y- maxima pattern under this condition. Under deformation of high- greenschist to low- amphibolite facies, quartz is dominated by type Ⅳ quartz ribbons and dynamically recrystallized grains of uniform optical feature and 120° tri- joint point. Plagioclase starts to display characteristics of deformation in brittle- ductile transition state. K- feldspar distinctly displays characteristics of ductile deformation. Quartz c- fabrics show typeⅠcross girdle pattern under this condition.

THE EVIDENCE OF THE SOUTH LONGMENSHAN FAULT ZONES CUTTING LATE QUATERNARY STRATUM

Yang Xiaoping, Jiang Pu, Song Fengmin, Liang Xiaohua, Chen Xiancheng, Deng Zhongwen

1999, 21(4):  341-345. 

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The Longmenshan fault zone is a boundary fault between the Tibet Plateau and western Sichuan foreland basin which controls the seismicity of the Longmenshan region. Two geological profiles had been dug in the south segment of Longmenshan fault zones. It is found that the reverse Wulong fault (south segment of the Longmenshan center fault zone), at the northern of Wulong village, offsets the stratum of TL age 92.0?7.2 thousand years, and is covered with the layer which TL age is 78.5?6.1 thousand years, the vertical displacement is 0.73m. The reverse Dachuan shuangshi fault (south segment of the Longmenshan front fault zone), at the northern of Daxi village, offsets the stratum which TL age is 57.4?4.5 thousand years, the height of the fault scarps is about 1.74m.

A STUDY ON ESR DATING FOR THE DASHUICHANG GOUGE PROFILE OF THE YISHU FAULT ZONE

Sun Yingjie, Lu Yanchou, Yin Gongming

1999, 21(4):  346-350. 

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Along the Dashuichang gouge profile of the Yishu fault zone, there are ten divided gouge stripes based on colors and textures of the gouge Thirteen samples for ESR dating have been collected from the various gouge stripes ESR dates of these samples range from 240ka to 530ka B P, and concentrated on two time intervals of 240～310ka and 410～530ka, respectively It means that there might be two major active episodes on the fault during the Quaternary period. The ESR dates of gouge quartz samples are consistent with geological evidence and intersection relationship on outcrop section.

DISCUSSION ON NEW ACTIVITY OF THE SECOND SONGHUAJIANG FAULT

Li Chuanyou, Wang Yipeng, Shen Jun, Zhang Lianghuai, Li Chunfeng

1999, 21(4):  351-360. 

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Along the southwest bank of the Second Songhuajiang river, from Xiwangjia to Hadashan, there are two patterns of stratigraphic variation. One is the faults and fractures of small scales of Quaternary. Another is the landslides of larger scales along the bank of the river. Detailed studies show that those stratigraphic alteration, faults and geofractures of Quaternary are not tectonism-genetic. They are mostly related to landslides. On the basis of analysing the geological characteristics, making use of the drilling, seismic reflection data and geophysical exploration results, it is suggested that the Second Songhuajiang fault had been inactive since Tertiary.

TOPOGRAPHIC SURVEY OF MICRO FAULTED LANDFORM AND ESTIMATION OF STRIKE SLIP RATE FOR THE ZEMUHE FAULT, SICHUAN PROVINCE

He Honglin, Song Fangmin, Li Chuanyou

1999, 21(4):  361-369. 

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Since the Zemuhefaultrejuvenated asthetransition faultbetween the Anninghefaultandthe Xi aojiang fault aboutin the Middle Pleistocene,it was dominated bystrongleftlateralslip and becameanim portantearthquakefault.Thelowestalluvialfantableland,which developed widespreadinthe Zemuhe val ley,isestimated to be 10 000 ～15 000 years BPbased on thermoluminesceneand 14Cdatingresults.Sever alfaulted streams, which cutthesurface ofthelowesttableland and should be youngerthan orasold asthe lowesttableland,areselected to belandform feature for determining the net tectonic displacement on the Zemuhefault and were surveyed. The average displacement of these streams was measured to be 86m. Therefore,the averagelateralslip rate of Zemuhefaultin the Late Pleistoceneis calculated to be 5.8 ～8.6m m/a.

INTERNAL CORRESPONDENCE ANALYSIS OF GRAVIMETRIC AND MAGNETIC DATA FOR THE NORTHERN PART OF SOUTH-NORTH TECTONIC ZONE

Yin Xiuhua, Li Yishi, Liu Zhanpo

1999, 21(4):  370-376. 

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The principle of internal corresponndence analysis(ICA) of gravimetric and magnetic data and geophysical foundation of geologic interpretation are presented. The plane curves of correlation coefficient R and slope α are calculated by ICA of gravimetric and magnetic data which are continued upward to 5km～50km in the northern part of south north tectonic zone. Combined with other geological and geophysical data, these analysis results are interpreted to reveal the feature of the crustal structures for the study area.

EFFECT OF ROCK STRUCTURE ON STATISTIC CHARACTERISTICS OF ACOUSTIC EMISSION

Liu Liqiang, Ma Shengli, Ma Jin, Lei Xinglin, Kusunose K, Nishizawa O, Jouniaux L

1999, 21(4):  377-386. 

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A comparative study on acoustic emission during deformation of two kinds of granites with different structures under triaxial compression is performed by using a new acoustic emission recording system with fullwaveform record and broaddynamic range. One is Inada aplitegranite of homogeneous structure from Japan and the other is Mayet granite with cemented natural joints from France. For the former granite, acoustic emission events are dispersed randomly and there is no clearly clustering along the major fracture. For the latter granite, acoustic emission events are mainly concentrated nearby the joint. Acoustic emission events occur synchronously with the volumetric dilatation in the former one but far earlier than the volumetric dilatation in the latter one. The two kinds of granite are also clearly different in the frequency spectrum of acoustic emission. The former has narrower frequency band and more highfrequency component, while the latter has wider frequency band and generally lower frequency spectrum. In frequencyenergy relation, the number of acoustic emission events in the former shows a welllinear progressive relation from highenergy level to lowenergy level and it shows an apparent intermittent or nonlinear variation in the middlehigh energy interval, with higher proportion of large events. It indicates that the rock structure has an apparent controlling role in the basic statistic characteristics of acoustic emission events. The cause for the phenomena may be that the different rock structures result in different deformation modes and processes.

FRICTIONAL HEATING BY STICK SLIP AND ITS SIGNIFICANCE FOR TL, ESR DATING

Li Ligang, Huang Peihua, Fu Rongshan, Huang Jianhua, Xu Yaomin

1999, 21(4):  387-396. 

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It is not appropriate to assume constant frictional stress and constant slip velocity for calculating temperature rise on fault during stick slip. Neither could the fault thickness be simply neglected. In most cases, frictional stress depends on rock and interstitial fluid properties. Five models of frictional heating are considered in this paper for various fault thickness, frictional stress and slip velocity which vary with time. The result shows that temperature rise is lower than those calculated by assuming constant frictional stress, constant slip velocity or zero fault thickness. This conclusion will remind scientists to pay attention to the result precise of TL and ESR dating.

STUDY AND EXPLORATION ON THE DASHITOU SONGSANTAI FAULT IN ANSHAN CITY,LIAONING PROVINCE

Gao Changbo, Zhong Yizhang, Wu Mingda, Zheng Shuangcheng

1999, 21(4):  397-405. 

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The Dashitou-Songsantai fault as the constitutive part of the regional fault striking NW is a hidden structure across Anshan city. Through synthetic geological exploration and field investigation it is found that this fault with 310～320° strike comes into urban area from Tenjiafanshen village and extends about 12.5 km, via traffic school, Songsantai village to the edge of Xialiaohe plain. The fault is 12.5km long, several tens cm to several m wide and has vertical dislocation of several m to several tensum.It is characterized by complex structure, changeable dip and varied morphological change. Somewhere it is a single fault and otherwhere 2～4 secondary faults which are parallel each other. Its newest age of acitivity is middle Pleistocene. It is not an active fault.

ESTIMATION OF THE SEISMIC MOMENT RATE BASED ON THE INCOMPLETE SEISMIC DATA

Shao Huicheng, Du Xingxin, Jin Xueshen

1999, 21(4):  406-410. 

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Considering the incompleteness of present seismic catalogs and the Poisson occurrence of earthquake validity of doubly truncated G-R relation, we improve the method for estimation of the seismic moment rate by using historical and contemporary and even archeological earthquake data. The seismic moment rates of several seismic zones in southwest China is calculated and compared with geological data. The results indicate the proposed method is feasible and practical.

THE INTENSITY CHARACTERISTICS OF ACOUSTIC EMISSION IN RUPTURE PREPARATION PROCESS OF THE SAMPLE INCLUDING HARD INCLUSION

Wang Bin, Xu Zhaoyong, Zhao Jinming, Yang Runhai, Mei Shirong

1999, 21(4):  411-416. 

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In this work, using the method determining the earthquake magnitude from coda wave continuous time, the intensity characteristics of acoustic emission in rupture preparation process of the sample including hard inclusion is studied. The results show that the intensity of AE is steady at the early pressuring stage. When the pressure reaches to 89% the rupture pressure stress, the intensity obviously increases; when the pressure comes up to 92% the rupture pressure stress and the intensity reaches the maximum value greater 20% than the value at the initial pressuring stage. Then the intensity falls, drops to the minimum value and relative quiet activity of AE appears at this time with the pressure increasing. With the pressure further increasing, the intensity rises again, following closely the main rupture occurs. As viewed from the space distribution of AE, AE occurs in the periphery of hard inclusion in the process from the steady value at early loading stage to the maximum and roughly appears in the hard inclusion and above it from the low value to recovering of the high value. At last the main rupture occurs and the inclusion rupture locally too, which is similar to the time progress in phenomenon before the Lancang-Genma earthquake.

A STUDY OF THE SHALLOW STRUCTURAL CHARACTERISTICS AND THE COUPLING RELATION BETWEEN DEEP AND SHALLOW STRUCTURES IN XINGTAI EARTHQUAKE AREA

Zhao Chengbin, Sun Zhenguo, Liu Baojin, Gu menglin, Leng Xinrong, Li Changfa, Li Deqing

1999, 21(4):  417-424. 

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The property and active age of the shallow listric faults in the epicentral areas are detected by the results of shallow and ultrashallow seismic prospecting in the epicentres of Xingtai M_s7.2 earthquake and M_s6.8 earthquake. It is suggested that the Xinhe fault(F₁) has not moved since Late Pleistocene epoch and the fault is not the earthquake generating fault. In addition, the paper discusses the deep and shallow construction patterns and their relation and it is affirmed that the earthquake generating faults are the high dip faults beneath the focus of the earthquakes in the light of the results of deep seismic reflection profiles and deep seismic sounding profiles in Xingtai area. The invading function of upper mantle magma produces additional stress field. Common effect of the additional stress field and regional tectonic stress field caused again the high dip fault action and the action caused Xingtai earthquakes. The earthquakes caused the motion of the shallow fault and surface material.

SHALLOW SEISMIC REFLECTION PROFILING WITH HIGH RESOLUTION IN YANQING HUAILAI REGION

Liu Baojin, Sun Zhenguo, Zhao Chengbin, Gu Menglin, Li Changfa, Leng Xinrong, Li Deqing

1999, 21(4):  425-430. 

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High resolution shallow seismic reflection measurements were carried out crossing deep faults which were revealed by deep seismic reflection profiles in Yanqing-Huailai region, and high-resolution images of shallow crust were obtained in this region. The results indicate that the sedimentary layer is characterized by good reflectivity and there are well developing shallow fault structures in this region. The basement of the basin consists of pre Sinian layers. It is characterized by irregular weak reflectivity and its depth is about 500～1000m. The Langshan fault is a listric fault on profile and is a controlling fault at the northern edge of Yanqing-Fanshan basin. It indicates stretching structure of a young developing basin.

ISOTOPE COMPOSTITIONS OF HE, AR AND ORIGIN OF ECLOGITE IN DABEI MOUNTAINS

Du Jianguo, Zhang youlian, Zhang Jianzhen, Chang Yonglian

1999, 21(4):  431-435. 

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This paper discusses the origin of eclogite in Dabei Mountains, eastern China based on the isotopic geochemical characteristics of helium and argon in garnet and omphacite. ³He/⁴He values are (1.19～4.63)×10^-7,and ⁴⁰Ar/³⁶Ar values have a wide range of 1209～4416. Ratios of ⁴He/⁴⁰Ar and ³He/³⁶Ar are 0.07～1.39 and (0.59～2.85)×10^-4, respectively. Primordial isotopes of helium and argon have been trapped in garnet and omphacite of eclogite. Helium isotopes are preferentially lost during retrograde metamorphic process. The isotope compositions of helium and argon of the eclogites are concordant with those of some mantle rocks, especially those of olivine and enstatite in the northern part of the continental rifted area of east China. The geochemical data of helium and argon show that the eclogites formed in depleted mantle, and may be a kind of " depleted mantle rock".

ACTIVE TYPES OF MODERN GEOTHERMAL FLUIDS AT THE TENGCHONG REGION, YUNNAN PROVINCE

Shangguan Zhiguan, Sun Mingliang, Li Hengzhong

1999, 21(4):  437-442. 

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In the Tengchong region, there exist two kinds of active geothermal fluids. Only those active geothermal fluids distributed at the Rehai Reshuitang and nearby areas of the Maan shan crater really deserve to be called the volcanic geothermal fluids. It means that their thermal source or the volatile components escaped from the geothermal fluid could be related to the modern volcanic activity or magmatic intrusion. Other geothermal fluids are all generally the thermal discharge caused by the tectonic activity. The ³He/⁴He≥1.2Ra could be the reliable indicator to distinguish these two fluids.

HOW TO DETERMINE THE MOST DOMINANT POTENTIAL SEISMIC SOURCE TO SEISMIC HAZARD AT SITES

Han Zhujun, Zhang Yuming, Yu Guihua

1999, 21(4):  443-451. 

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How to determine the most dominant potential seismic source(PSS) to seismic hazard at site is discussed, taking Qinghe Town(E116.33?,N40.03?) and the dam of Miyuan reservoir, Beijing as examples. The most dominant PSS is same at different periods for Qinghe Town site and it is Beijing PSS located by the site. When the site is the dam of Miyuan reservoir and the annual exceedence probability is less than 1.00E-2, the most dominant PSS is Huairou PSS located by the site for period (0.1s), but the most dominant PSS is Xiadian PSS for period (1.0s). The change also shows that the closer PSS has more important effect at short period (for exapmle,T=0.1s) and the distant PSS is opposite. To distinguish the most dominant PSS at different periods is significant in determining scenario earthquake or designed earthquake to calculate duration time of ground motion.

QUICK DETERMINATION OF EPICENTRAL REGIONS USING AIRBORNE EARTHQUAKE DISASTROUS SAR IMAGE CHARACTERS

Yang Zhe, Ren Defeng

1999, 21(4):  452-458. 

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Based on sampling damaged building rate of destroyed region identified by using Airborne SAR image with 3m or 6m resolution, this paper presents the method of quick determing epicentral areas with the reference of damaged building rates and its intensity response models of 3 types of earthquake. Its results are very helpful for the quick response to the earthquake emergency decision-making.

HORIZONTAL DEFORMATION OF CHINESE CONTINENT OBTAINED BY GPS SURVEY

Yin Shaofeng, Huang Liren, Guo Liangqian, Zhu Wenyao

1999, 21(4):  459-464. 

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Baseline changes of 1994-1996 between 19 GPS points across the country have been observed through remeasurement. The data indicate that deformation of western China is much greater than that of eastern China. In the west most of the baselines of NE or nearly SN direction are shorten and those of NW or EW direction are extended. In North China the NE and EW baselines are shorten while NW baselines are extended. In south China most of NWW baselines are shorten and NE baselines are mainly extended. Orientations of shorten baselines are roughly consistent with the P axis of focal mechanisms while that of extended baselines are in general normal or oblique to the P axis.

APPLICATION OF THE FUSION METHODS FOR MULTISOURCE DATA OF SATELLITE REMOTE SENSING IN GEOLOGY

Shan Xinjian, Ye Hong, Chen Guoguang, Wang Changlin

1999, 21(4):  465-472. 

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We present some kinds of satellite remote sensing data which are are often used and their characters. The fusion methods at some levels for different types of remote sensing data and other geoscience data are expounded. It is demonstrated by several application samples that the data fusion methods are helpful to make the characteristic informtion of geology be more prominent.