Table of Content

06 September 1989, Volume 11 Issue 3

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Brief Report

THE FUZZY RECOGNITION OF PRECURSORY ANOMALIES OF GROUNDWATER LEVEL BEFORE TANGSHAN M=7.8 EARTHQUAKE

Zheng Xi-ming, Feng De-yi

1989, 11(3):  1-8. 

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By using the method of membership function of fuzzy set, which is also called the direct method of fuzzy recognition, we have collected and analysed the data of ground-water level in more than 30 wells located in the Beijing-Tianjin-Tangshan area before and after the 1976 Tangshan earthquake (M = 7.8). The results obtained show that the long and intermediate-term anomalies of groundwater level in wells before Tangshan earthquake are difficult to discover but the short-term and imminent anomalies can be recognized obviously. Moreover, the more the time is closed to occurrence of great earthquakes, the more wells show underground level anomalies.

JURASSIC AND CRETACIOUS PALEOMAGNETISM OF THE TARIM BLOCK

Zhang Zheng-kun, Li Yong-an, Li Qiang, Zhai Yong-jian, Li Yian-ping, Michael McWilliams, Allan Cox, Robert Sharps

1989, 11(3):  9-16. 

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Two Mesoxoic sections along the northern margin of the Tarim block of China were studied paleomagnetically. One Late Cretaceous redbed section of 180 meters, lying 100 km north of Kuche (lat. =41.5°N, long. =83.5°E)gives a mean paleomagnetic pole position at lat.=63.0°, long. = 210°(N = 5, α₉₅ = 16°). The two lower sites within the section show reversed magnetic polarity. Another Late Jurassic to Early Cretacious sandstone section of 75 meters, lying northwest of Baicheng (lat.=41.8°N, long. =82°.E), yields a mean paleomagnetic pole at lat. =65°, long. =:209°(N = 6, α₉₅ = 9°.). Although the poles from two sections are significantly different before tilt corrections, they become superimposed each other after tilt corrections, suggesting a positive fold test at 99% confidence level. Thermal demagnetization experiments remove the present earth field components in temperature ranges before 500℃ and exhibit unblocking temperatures around 675℃, indicating the main magnetic mineral in samples to be hematite.The new paleomagnetic results suggest that the Tarim block does not experience large tectonic movement between Late Jurassic and Late Cretacious. The new Cretacious poles of the Tarim block are in good agreement with the Cretacious poles for North and South China Blocks (Lin, 1984), and South Korea (Lee et al., 1987) , suggesting no post-Cretacious relative motion between the Tarim block and eastern Asia. However, the Cretacious ploes of the Tarim block are significantly different from those of the Siberian block, suggssting that there is a post-Cretacious relative motion. This relative motion can be explained, in one way, as the northeastward motion of the Tarim block with respect to the Siberian block since Late Cretacious.

THE DISTRIBUTION OF HEAT FLOW DATA IN THE CONTINENTAL AREA OF CHINA AND ITS PRELIMINARY STUDIES

Huang Shao-peng

1989, 11(3):  17-26. 

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In this paper, 167 heat flow values with detailed measurememt data published so far in the continental area of China have been collected and used for statistic analyses. The geographical distribution of the heat flow sites in the area is quite uneven. The heat flow values vary from 25 to 245 mWm^-2. Several methods have been employed to calculate the average heat flow. The results indicate that the representative heat flow for the continental area of China would lie in the range of 61 to 68 mWm^-2.A new data analysis method has been developped in the present work. Firstly, mean heat flow values for 1白1? longitude-latitude grids are calculated. Secondly, the mean grid values are used to average the mean values for the corresponding longitude and latitute strip, denoted as longitude and latitude heat flow separately. The results reveal that the difference between the. variations of longitude and latitude heat flow is significant. The variation of latitude heat flow seems to be characterized by a wave pattern. This phynomenon has been confirmed by the heat flow data from Japan and its surrounding oceanic area, which have also been reviewed in the same way. The wave pattern of latitude heat flow is shown not only in a stable wavelength of about 5?, but also in the well consistent wave cycles identified in the two areas. The author believes that the origin of the comparable latitude heat flow wave pattern is unlikely in the lithos-phere itself, but likely in the asthenosphere. Some geological and geophysical implications of the wave pattern have been briefly discussed.

RATES OF HOLOCENE VERTICAL MOVEMENTS OF FAULT BLOCKS ALONG THE COAST OF FUJIAN PROVINCE

Yu Zhao-kang, Wu Xi-Hang

1989, 11(3):  27-33. 

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Based on the 78 ¹⁴C data of sediments related to the former sea levels, and by means of linear relation, we have calculated the rates of vertical movements of following faulted blocks: (1) the coast of northeastern Fujian Province (including Fuding, Ningde, Luoyuan, and Lianjiang Counties); (2) Fuzhou Basin and Coastal Plain of Changle County; (3) Longtian-Gaoshan Peninsula of Fuqing County and Pingtan Island; (4) Coastal Plain of Putian; (5) Deltaic Plain and estuary of the Jiulongjiang River; (6) Coast of southern Fujian Province. The vertical movements of the faulted blocks during Holocene are characterized by uplifting with average rate from 0.8 to 2.8 mm/yr and can be comparable to the rates of crustal deformation obtained by leveling measurements.

SOME GEOCHEMICAL CHARACTERISTICS OF GASES IN WUDALIANCHI VOLCANIC REGION

Zhao Yi, Kong Ling-chang

1989, 11(3):  34-36. 

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ANALYSIS OF RECENT FAULT ACTIVITY AT XIALATOU ON THE XIANSHUIHE FAULT

Ge Pei-ji

1989, 11(3):  55-63. 

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In this paper, the faulting tendency and annual circle variation were analysed on the basis of short range leveling and baseline data at the Xialatou field across Xians-huihe fault zone.Distribution of fault activity on the main crack zone and the surrounding areas was discussed. In addition, model of fault activity is given.

THE AGE OF NEW ACTIVITY OF YIDU AND MENGSHAN FAULTS

Wang Hua-Iin, Cui Zhao-wen, Wang Li-jun

1989, 11(3):  64-64. 

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EARTHQUAKES AND BEDROCK SLIDES IN THE HUOSHAN REGION

Xia Hao-ming, Xi Shu-fong

1989, 11(3):  65-72. 

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The bedrock slide is an important apptarance of the seismicity in Huoshan region. The small to medium shallow focus earthquakes occur frequently in this region, which is well-known as "the seismic window" of North China. The earthquakes have close relations to the change of stress field in North China and the bedrock sliding. The bedrock sliding has caused the occurence of earthquakes, while the Latter has given rise to the bedrock slide too.

DEFORMATION RELICS OF THE 1556 HUAXIAN (SHAANXI,CHINA) GREAT EARTHQUAKE AND THE STUDY OF PALAEOSEISMICITY ON THE FRONTAL FAULT ZONE OF THE HUASHAN MTS

Zhang An-liang, Mi Feng-shou, Chong Jin

1989, 11(3):  73-81. 

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Since the late Quaternary Period, there have been conspicuous neotectonic activities on the frontal fault zone of the Huashan mts. The strong deformation damage relics due to earthqnake, such as new fault scarps, base rock fractures, loess crevices, and land slides are distributed along the fault zone and nearby. The frontal fault zone must be the genetic fault of the 1556 Huashan earthquake (M = 8).Based on the analysis of a palaeoseismic profile, it is supposed that four great earthquakes have probably occurred since the Holocene Epoch, the recurrence interval being about 2000-2500 years.

⁴⁰Ar-³⁹Ar AGE OF TRACHYTE ZGC FROM ZOUMAYING,NANHAI COUNTY,GUANGDONG PROVINCE

Li Da-ming, Chen Wen-ji, Wang Xin, Li Qi

1989, 11(3):  82-84. 

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GROUND FISSURE IN THE CITY OF XI'AN

Wang Jing-ming

1989, 11(3):  85-93. 

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The ground fissure in the City of Xi' an show leftlateral and are characterized by prevailing orientation, en echelon, roughly constant step-intervals and southern blocks relatively falling down. The fissures have originally been created sporadically by the regional stress field and consequently enlarged by the groundwater activity. Tha appearance of fissures seems earlier in the north and gradually migrates to the south. The slips along these fiasures are not uniform, but with quaci-peroods of 4,20,400 and 750 years respectively, which seemingly correlate with the periods of seismicity in the region. This indicates that the ground fissures and earthquakes both are under the control of the same regional stress.

SYMPOSIUM ON THE NEOTECTONICS IN EASTERN CHINA HELD IN YICHANG

Lei Yao-qi

1989, 11(3):  94-94. 

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CHARACTERISTICS OF CLAY MINERALS IN FAULT GOUGES FROM HONGHE FAULT ZONE AND THEIR SELSMOGEOLOGLC IMPLICATION

Zhang Bing-liang, Feng Jin-jiang, Niu Luan-fang, Hu Bi-ru

1989, 11(3):  96-97. 

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