Table of Content

07 June 1989, Volume 11 Issue 2

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Brief Report

A TENTATIVE APPROACH OF RUPTURE SLIP PROCESS OF THE 1932 CHANGMA EARTHQUAKE

Liu Zhong-fang

1989, 11(2):  1-6. 

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Based on the investigation and analysis of the macroscopic ground rupture zone caused by Changma earthquake(M_s =7.5)which occurred in the western Qilian Mountains, Gansu province on December 25, 1932. and combining the information relative to fault activity with the results of lab modelling experiments, this paper pays much attention to the discussion of the tectonic evolution of Changma causative fault and the rupture slip process at the places of stress concentration within seismogenic fault.The rupture zone on ground caused by the event, with a NWW of trend and a length of more than 120 km, consists of three reversed-S-shaped seismic demation belts, and coincides with the Quaternary active trace of Changma faults. Both field geological information and modelling experiments have indicated that the concaves of the turning sectors of the reversed-S-shaped faults are the places at which the stress and strain would be concentrated easily. Here, a model of the multi-initiative points of the rupture slip within Changma seismogenic fault has been suggested, i. e., when the Changma event occurred, each of the concaves of the above kinds ruptured initiatively, then was developing along the above-mentioned reversed-S-shaped fault's trace so as to form the whole Changma seismic fault.

PATTERN RECOGNITION APPLIED TO IDENTIFY DESTRUCTIVE EARTHQUAKE-PRONE REGIONS IN EAST CHINA

Xie Hua-zhang, Wang Ai-ling, Yang Cai-xia

1989, 11(2):  7-15. 

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Using the modified Cora-3 pattern recognition algorithm established by I.M.Gel-fand et al., we have studied the related date in tectonics, geomorphology and geophysics to identify destructive earthquake-prone regions in East China(30?-35癗, 116?-123癊). The results are satisfactory.Seven D (Dangerous) and eight N (Non-dangerous) "characteristic traits" are selected from sixteen original features. The geological meanings of the traits are analyzed. It shows that destructive earthquakes in East China often occur in such regions as inside subsidence areas during the neotectonic period, inside or in the margin of Cretaceous or Cainozoic structural/faulted-down basins, near the boundaries of the blocks having vertical neotectonic movement of contrasting nature, as well as where there are abundant active faults. In the above-mentioned regions some degree of geophysical anomalies generally appears at the same time.The mis-identifying rate in the course of "Voting" is low. By voting we have zoned five earthquake-prone regions in East China. The conclusions are confirmed by the control experiments.

A PIONEER OF THE CHINESE SEISMOGEOLOGICAL STUDY——CENTURY ANNIVERSARY OF WENG WEN-HAO'S BIRTH

Pan Yun-tang

1989, 11(2):  16-18. 

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A STRONG EARTHQUAKE EVENT OCCURRED IN ANCIENT TIME IN BEIJING-TIANJIN-TANGSHAN AREA

Zhao Gen-mu, Wang Ruo-bai, Liu Yu-tian, Zhen Wen-jun

1989, 11(2):  19-25. 

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The traces and tectonic deformations of palaeoearthquake event hurried in Holocene strata in Beijing-Tianjin-Tangshan area have been studied in this paper. The study of Holocene strata and palaeo-environment suggests that the event occurred in the time when Holocene transgression ended in North China and coincided with a legend of disaster in ancient time 4000 years ago. Some phenomena related to this palaeo-earthquake have been discussed in this paper,such as seismic tectonic background, liquifaction of sandy basic in the strata, epicentre and magnitude of this event.

VIBRATION CHARACTERISTICS ON THE BOTH SIDES OF VALLEY IN JIAOJIAPING EARTHQUAKE AREA OF WUJIANGDU RESERVOIR

Yang Qing-yung

1989, 11(2):  26-32. 

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The amplitude and peak period of earthquake wave spectrum increase with elevation rising on both sides of valley in the Wujiangdu reservoir Jiaojiaping earthquake area. Elevation rises a hundred meters, the amplitude increases about one times. Peak period of spectrum increases 0.1-0.3 second. The amplitude is related with earthquake incident direction. The amplitude on the sides nearer to epicenters is much larger than opposite one. According to relation between intensity and displacement amplitude of earthquake, it is suggested that if build a hundred meter dam, the intensity at the top would be 0.5-1.0 degree higher than in the bottom.

THE "EARTHQUAKE WINDOW" AND ITS MECHANISM AT ZHANGZHOU-HUAAN, FUJIAN PROVINCE

Lu Hao-jing, Yang Zhi-hui, Chen Hui-qiong

1989, 11(2):  33-38. 

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The Zhangzhou-Huaan is an active region of moderate earthquakes, where earthquakes occur frequently today. Based on analysing characteristics of historical and earthquakes in the region, we find that there is a correlation to a fixed extent of seismic activities between this region and Fujian-Taiwan region. We thus name this region as "earthquake window". And the formation of this "earthquake window" is closely related with an upward force provided by the heat from the deep of earth.

ON THE SEISMOGEOLOGICAL CONDITIONS FOR YANGZONGHAI THERMAL POWER PLANT, YUNNAN PROVINCE

Wang De-ming, Kong Lin, Yang Mei-e

1989, 11(2):  39-45. 

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The Yangzonghai thermal power plant is located in Xiaojiang strong seismic zone, Yunnan province. Fundamental earthquake intensity of the area is Ⅸ degrees. This puts a great constraint on the further extension of the plant, which is necessary to make full use of the favourable power supply to Yunnan province.The Xiaojiang fault zone consists of two branches (the east and west branches) and the site of the plant is located in between both of them being strong seismic activity zone in history. An earthquake of magnitude 8 occurred in 1833 near Song-Ming county on the west branch.A geological cross-section was dug in Dongguyayin village, it is found that the recurrence for magnitude 7 is at least 300 years and magnitude 8 is at least 1000 years. So there is little possibility for an earthquake over magnitude 7 to occur in coming 100 years.Geomorphologically plant area is shown as terrace, with a low relief. The bedrock consists of dolomite. The rock formation gently dips away from the lake Yangzonghai and underlies the red clay. The underground water level is deep. All of these suggest that the foundation of the plant is steady, more beneficial for antiseismic building.As stated above, it is clear that the fundmental earthquake intensity of the Yangzonghai power plant can be lowered from Ⅸ down to Ⅷ degrees.

CONTEMPORARY ORIENTATION OF TECTONIC STRESS FIELD IN THE JIANCHUAN DETERMINED FROM THE BOREHOLE BREAKOUTS

Zhai Qing-shan, Mao Ji-zhen, Zhang Jun, Wei Qing-yun, Li Fang-quan

1989, 11(2):  46-52. 

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The mechanism of borhole breakouts, its formation environment and relation with the present-day tectonic stress field are presented in this paper; The logging principle of ultrasonic borehole televiewer, operating techniques and analyzing method of borehole breakout data are also described. In high seismic area of Jianchuan, the orientation of the maximum horizontal compressive stress is N20癊 determined by the borehole breakouts obtained from the ultrasonic borehole televiewer logging data in an 800m deep well, It is very consistent with N15癊 of those measured using the hydraulic fracturing method in the same well.

THE VARIATION OF THE UNIVERSAL GRAVITATIONAL CONSTANT AND THE DISTRIBUTION OF EARTHQUAKES IN CHINA THROUGH TIME AND SPACE

Bruce Denness

1989, 11(2):  53-65. 

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Earthquakes are devastating natural disasters: no place on Earth experiences them to a greater extent than China and the East Asian seaboard. Similarly drought, floods and other climatic hazards are frequent events around the World. A theory is developed here to link these two geophysical phenomena.During the early 1980' s a deterministic analytical model of climate variation was developed. It matches proxy palaeoclimatic time series and can also be used for forecasting; it has been successfully tested for several years. Earlier substantiation of the model over geological timescales is here extended through recent history. An explanation of the cause of climate change is then suggested based on the possibility that the Universal Gravitational Constant (G) may vary with time. Variation of G implies simultaneous variation of both tectonic activity, such as earthquakes, and climatic properties; such as the global temperature represented by the model. The model therefore also holds promise for earthquake forecasting.A theory is proposed to explain the alternation of earthquake activity between different areas over a period of time. This is tested in hindcast for the many twentieth century earthquakes of Magnitude 6 or greater on the Richter scale in China. Within the limitations of the accuracy of small scale topographic mapping and suspected insensitivity of epicentre location, the results are most encouraging.

PRELIMINARY REPORT ON A PALEOSEISMOLOGICAL SECTION, HUANGTUYAO, HUAILAI, HEBEI PROVINCE

Fang Zhong-jing, Cheng Shao-ping, Wang Jing-bo, Li Zhi-yi, Yuan Zhu-zhong

1989, 11(2):  66-68. 

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ON THE GRAVITY GRADIENT BELT OF LONGMENSHAN MTS——A SIMULTANEOUS COMMENT ON THE DEEP STRUCTURE CHARACTERISTICS OF THE SEISMIC REGION OF SONGPAN-PINGWU-DIEXI

Liu Guang-xia, Zhao Wen-jing, Ren Wen-ju, Wu Xiu-yun

1989, 11(2):  69-78. 

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In this paper, the results of 3-D normal and inverse gravity calculus had been-analysed and interpreted, and it was suggested that the gravity gradient belt of Long-menshan Mt. is not a simple slope or steep step and that a serious of deep seismo-geological problems, such as the rang of the gravity gradient belt, the relationship between shallow/deep forms of the seismic-faults, and the complicated sub-structures of the whole mentioned gravititional gradient belt should be studied and understood further. Close coordinate between the two disciplinaries of seismo-geology and geophysics can perhaps-answer the mentioned problems. Such a way of research can also discover the regularity of pregnancy and occurrence of strong earthquakes in the gravity gradient belt of Longmenshan Mt. as well as the whole North-South seismic activity region. They are significance for the earthquake prediction and for the engineering seimology, and the-contents of geotectonics will be enriched.

HORIZONTAL DEFORMATION FIELD IN HUAILAI- YANQING AREA

Zhang Lian-jia, Huang Li-ren

1989, 11(2):  79-84. 

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The major features of horizontal deformation in Huailai-Yanqing area are studied using the triangulation and trilateration data which were obtained in 1966 and 1986 respectively.

DISTRIBUTION AND FOCAL MECHANISM OF EARTHQUAKES AND STRESS STATE ON KURIL ISLANDS AND SEA OF OKHOTSK

Wu Zhong-Hang, Zang Shao-xian

1989, 11(2):  85-95. 

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The distribution of earthquakes of M_b≥4.0 from 1971 to 1982 were studied using the data from I.S.C.; 43 focal mechanisms were obtained using the first motions of compressional wave from I.S.C and the network of the Chinese earthquake observatories. The earthquakes are distributed mainly in an arc-like belt along Kuril islands. There is an obvious Benioff zone beneath Kuril islands and Kamchatka. The depth into which the Benioff zone extends is different in different parts of the Benioff zone. The maximum depth is about 619km and the minimum depth is about 180km. The dip direction of the Benioff zone is about NW55° and the dip angle is about 45°.The P axes of focal mechanisms for earthquakes in the crust in both sides of the trench are in the NW direction and nearly horizontal, reflecting the compression from the Pacific plate. The stress state on the subduction zone varies with depth: Above-114km, the T axes of focal mechanisms are nearly consistent with the direction of subduction; in the range of depths from 114km to 175km, the focal mechanisms are divided into two groups: one is that the T axes coincide with the direction of subducting and P axes are nearly horizontal, another is that the P axes coincide with the direction of subducting and T axes are nearly horizontal: In the range of depths from 175km to 220km, the P axes are coincident with the direction of subduction; From 320km to 440km, P and T axes are not as good in gathering as in other depths, but the P axes appear to be close to the direction of subducting; In the depths from 515km to 619km, the P axes are coincident with the direction of subducting. The reason for the stress state was also discussed.

HAOKENG GROUND FISSURE IN ZHANGZHOU AND ITS TECTONIC IMPLICATION

1989, 11(2):  96-98. 

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