Table of Content

04 March 1981, Volume 3 Issue 1

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Brief Report

TANGSHAN GREAT EARTHQUAKE AND ITS FORSHOCKS AND AFTERSHOCKS

Wu Kaitong, Li Ziqiang, Jin Xieshen, Chen Guangying, Lu Peiling, Cao Xinling, Tian Kangyuan

1981, 3(1):  1-9. 

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This paper deals with the determination of seismic parameters of the Tangshan earthquake and its geological background, and also discusses characteristics of microshocks before the main shock, such as seismic gap, shock-concentration-quiescence, b-value decrease and the strip-distribution of shocks and so on.According to the surface rupture trend caused by this earthquake, the initial motion pattern of P-waves, the vertical deformation both before and after main shock and the distribution of aftershocks etc. we supposed that the Ms 7.8 earthquake probably was a result of the horizontal dextral movement of NE trending fault, and the Ms 7.1 earthquake was caused by the horizontal sinistral displacement of nearly SN running Luan-he fault which was dragged by the NE fault.From the characteristics of space and time distribution of aftershocks in Tangshan area, the focal rupture process and its influence on the aftershocks were discussed in this paper. Finally, it is suggested that the occurrence time of Tangshan earthquake was probably associated with the current astronomic conditions.

THE CHARACTERISTIC OF HYDROGEN ISOTOPE IN NATURAL WATER IN BEIJING REGION

1981, 3(1):  10-10. 

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EXPERIMENTAL STUDIES OF THE PROCESS OF FRACTURE AND ACOUSTIC EMISSION IN A FAULT ZONE

Ma Jin, Xu Xiuqin, Zhang Botao, Liu Tianchang, Wu Xiuquan, Wang Baosheng

1981, 3(1):  11-17. 

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From the features of fracture and acoustic emission and the stress-strain behavior this paper indicates that the activity of a fault zone depends on the angle of the fault plane with soft sandwich and the axis of principal compressive stress. Our experiments provide evidence that as this angle is larger than 45℃, the process of fracture has three stages, and before main shock there occurred a number of foreshocks and took place apparent dislocation within the fault zone and its surroundings. On the other hand, as the angle is smaller than 45? these phenomena then would be disappeared.

PRELIMINARY STUDY OF THE HOT SPRINGS AND SEISMICITY IN FUJIAN, GUANGDONG AND JIANGXI PROVINCES

1981, 3(1):  18-18. 

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STUDY OF RECENT TECTONIC STRESS FIELD IN JIANGSU-SHANDONG-ANHUI-HENAN REGION FROM THE FOCAL MECHANISM SOLUTIONS

United Group of Focal Mechanism

1981, 3(1):  19-28. 

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Based upon the statistical studies of focal mechanism solutions of 37 moderate-small earthquakes (Ms = 2.1-6.0) during the period from 1973 to 1977 in Jiangsu-Shandong-Anhui-Henan region, the preferred principal compressive stress of recent tectonic stress field is in NEE (about 76?)and the tensile stress in NNW (about 344?).Considering that both the long axes of isoseismals for some moderate-small shocks and the Late Tertiary faults are characterized by a NNE trend in predominance, we inferred the new-formed seismic rupture to be successive. Finally, this paper discusses the differeence between the recent tectonic stress fields in its northern and southern part.

HUTUO RIVER TERRACES IN TAIHANG CANYON SECTION AND QUATERNARY TECTONIC MOVEMENT

Cheng Shaoping, Ran Yongkang

1981, 3(1):  29-39. 

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The investigation of river terraces is an effective way to explain the neotectonic movements. The data obtained by detailed survey of Hutuo River terraces in Taihang canyon section show that there are four terraces in this river section, reflecting four intermittent uplifted movements since Quaternary. These terraces were offset and deformed by Jiazhiwan fault, along which the uplifted Xizhou-Taihang fault block was tilted. It is suggested that the northern segment of Taihang fault block is still following the natures of Pliocene movements, and the present regional tectonic stress state does not show any essential changes.

THE CHARACTERISTICS OF DEVIATION OF RATIO OF S WAVE TO P WAVE FOR THE DIFFERENT TYPE OF EARTHQUAKE SEQUENCES

Zhao Xiurong, Ye Wenyan

1981, 3(1):  40-40. 

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ON THE TEXTURE AND FABRIC OF SOME LHERZOLITE NODULES IN CAINOZOIC BASALT FROM EASTERN CHINA

He Yongnian, Lin Chuanyong

1981, 3(1):  41-50. 

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The ultramafic nodules widely distributed in Cainozoic basalt in eastern China are regarded as fragments of upper mantle that were brought up to the ground surface by basaltic magma. It is suggested that the study of this kind of nodules would offer some direct information about upper mantle. The textures of some spinel lherzolite nodules collected from some regions in eastern China were discussed in this paper. Three main types of texture can be distinguished, such as coarse granular, porpbyroclastic and granuloblastic. Their fabrics were also analysed. And the preferred orientation of minerals indicates that the coarse granular type is lacking in orientation, whereas the porphyroclastic type has distinct orientation, and the lalter’s fabric feature is followed by the granuloblastic type with some variation. Thus, the coarse granular-porphyroclastic-granulobla-stic transitional sequence has been established. Moreover, the textures and fabrics of Alpine type of peridotite from a suite of ophiolite formed by emplacement are comparable with these kinds of nodules, it enables us thus to further infer their mantle origin.

ON THE ENVIRONMENT AND GEOLOGICAL AGE OF TWO ORES IN BEIJING REGION FROM SPORO-POLLEN ANALYSIS

Yan Fuhua, Ye yongying, Mai Xuishun, Liu Yuexia

1981, 3(1):  51-65. 

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The two peat sections are situated in the Xiaowangzhung, Yanqing County and Xinglitum, Haidian district, respectively.Many pollen grains of arboreous, shrubs and herbaceous plants are found in the peat sediments. They belong to the genera Pinus, Querous, Betula, Ulmus, Tilia, Ephedra, Artemmisia etc. and families Chenopodiaceae Gramineae Cyperaceae Compo-sitae etc.Three vegetation phases from the lower to upper parts of the sections may be distinguished by the pollen analysis. The lower part of the sections represents a coniferous forest phase, mainly consisting of Pinus or the coniferous-broad forest phase of Pinus and Betula, while the middle and upper parts represent the coniferous-broad forest phase, mainly consisting of Pinus, Querous, Betula, Ulmus and Tilia and coniferous forest phase of Pinus, respectvely.The results of pollen analysis show that the climate was changing during the formation of the peats. In the early stage the prevailing climate was warmer and drier, in the middle stage was the warm and moist climate and in the late stage was the cooler and drier climate dominated.Based on the polynological date C¹⁴ age deteminalion, the geological ages of two peat ore sections are described as the Early Holocene for the lower part, the Middle and Upper Holocene for the middle and upper parts respectively.

THE AGE OF FORMATION OF THE MARINE SHELLS AND BEACH ROCKS IN THE YINGGEHAI REGION, HAINAN ISLAND

Zhang Jingwen, Li-Guiying, Zhao Xitao

1981, 3(1):  66-66. 

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SOME PALEOSEISMIC EVIDENCE IN THE NORTH CHINA REGION

Ding Menglin

1981, 3(1):  67-74. 

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In this report some evidences of ancient earthquakes found in the North China region are presented as follows.1. the ruins of ancient cities in the Hang dynasty distracted by the earthquakes having occurred in the area northwest of Dengkou County, Nei Monggol Autonomous Region; 2. The offset of Great Wall and fault scarps by the ancient earthquakes in Hungguozigou area northwest of Pinglo County, Ningxia Autonomous Region; 3. The paleoseismic faults and liquefaction and deformation of sandy ground in Guchenzi area, Zhongning County, Ningxia Region; 4. Landslide zones in loess caused by the ancient earthquakes in the Tianshui-Baoji-Changxing region; 5. Seismic fissures and rock falls in Haicheng County, Liaoning province; 6. The folds and deformation of lacustrine diatomite layer by earthquakes in Lingqu County, Shandong province; 7. Paleoseismic fissures in Xingyi County, Jiangsu province. These results are of significance in regional seismic evaluation.

FOCAL STRESS FIELD AND TECTONIC STRESS FIELD OF THE XINFENGJIANG RESERVOIR INDUCED EARTHQUAKES

Wei Bailin

1981, 3(1):  75-79. 

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The focal stress field of the Xinfengjiang earthquakes shows that the T-axis constantly trends towards NNE and is nearly horizontal, but the P-axis rotates from 0? to 180癷n a vertical plane perpendicular to the T-axis. Under the N-S horizontal tectonic compression the focal stress field is induced by a left-lateral transform fault at Heyuan resulting from the relative sliding between the rock mass in the reservoir area and on its southern side at different rate.

THE NORMAL DYNAMIC CHANGES OF RADON IN WATER OF SOUTHEASTERN FUJIAN

Yu Zhaokang, Cai Shihuang, Lin Jiatao

1981, 3(1):  80-80. 

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