• Volume 6,Issue 3,1984 Table of Contents
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    • SOME ABNORMAL PHENOMENA OF THE IONOSPHERE PRIOR TO SOME GREAT EARTHQUAKES IN CHINA

      1984, 6(3):1-11.

      Abstract (554) HTML (0) PDF 680.82 K (708) Comment (0) Favorites

      Abstract:In this paper some abnormal phenomena of the ionosphere which occur before and after great earthquake have preliminarily summarized. It is shown that the abnormal disturbances of the ionospheric form are a general phenomenon when earthquake is approaching and, secondly, there exist unusually temporal and spatial disturbances of "highpoint displacement" for F layer. They may associate with the nonuniform "electron cloud" of the ionosphere locally, formed and with the geomagnetic field and the geoelectric field as well as the electric properties on the surface. Further observations and studies on them would be helpful to estimate the region and approaching time of earthquakes. The relationship between the ionosphere and geomagnetic field and the earthquake are also briefly discussed. It is pointed out that the relationship may be due to the match effect of geomagnetic field.

    • CHARACTERISTICS OF EARTH-RESISTIVITY BEFORE AND AFTER THE HAIYUAN EARTHQUAKE OF MAGNITUDE 5.5 ON APRIL 14, 1982

      1984, 6(3):12-20.

      Abstract (513) HTML (0) PDF 610.62 K (527) Comment (0) Favorites

      Abstract:In this paper we investigate the characteristics of earth-resistivity before and after the Haiyuan earthquake of magnitude 5.5 on April 14, 1982. The results are as follows:
      (1) Before the shock the descending in ρs-changes appeared universally in certain areas. But the imminent-term ρs anomalies dropped or rose. The large amplitude and the high rate were responsible for imminent-term anomalies. The stages of ρs-changes before and after the earthquake were:descending-levelling-sudden jitter for impending earthquake-(quaking)-recovered.
      (2) A feature of ρs-trend anomalies before the shock appeared to be large area and a long time. On the other hand, the direction of the maximum anomalous value of every station corresponded with the strike of the local large fault (or the earthquake fault). These characteristics showed that the ρs-trend anomalies reflected the rapid increase of intensity in the regional stress field.
      (3) The ρs-anomalous amplitude of every station is closely related to Quaternary system overburden around a station. The thicker the overburden, the smaller its anomalous value will be. Therefore, it needs to have the better underground conditions of stations for forecasting the intermediate magnitude earthquake.

    • ONE POSSIBLE KIND OF SHORT-TERM FORESHOCKS

      1984, 6(3):21-26.

      Abstract (553) HTML (0) PDF 351.13 K (669) Comment (0) Favorites

      Abstract:Researching the distribution of small earthquakes with ML≥2, we have discovered that before the Luhuo earthquake with magnitude 7.9 on Feb. 6, 1973, the Liyang earthquake of M=5.5 on April 22, 1974 and the Longling earthquake of M=7.3, 7.4 on May 29, 1976, during about three months, the small shocks with ML≥2 occurred one by one along a circle migrating turn left(for the Luhuo earthquake of M=7.9 and the Longling earthquake of M=7.3, 7.4) or right(for the Liyang earthquake of M=5.5). The Liyang and Longling main shocks happened inter or near their circles, but the Luhuo main shock happened outside its circle. The Luhuo main shock and its small earthquakes circle located in the same tectonic zone.
      According to that the sum of square roots of energy for small earthquakes at circles has partly increased quickly with time nonlinearly, we may conside it as a short-term foreshock.

    • CERTAIN SHORT TERM ANOMALOUS VARIATIONS OF THE CHARACTERISTICS OF SEISMIC WAVES BEFORE THE KUERLE EARTHQUAKE (M=5.8)

      1984, 6(3):27-34.

      Abstract (496) HTML (0) PDF 517.43 K (438) Comment (0) Favorites

      Abstract:In this paper, we make a preliminary analysis of certain short-term anomalous variations of the kinematics and dynamies of seismic wave before the Xinjiang Kuerle earthquake(M=5.8, April 22, 1958).
      Using the amplitude ratio s of p and waves, duration ratio, anomalies of the seismic vilocity in the anomalous regions microearthquakes are discussed.
      The results from the observational data show that there are clear anomalous variations of the characteristics of seismic wave before the strong earthquake. Therefore, to study of characteristics of seismic wave may be helpful for understanding the physical process of source and prediction of the strong earthquake.

    • MOMENTARY FLOW MECHANISM OF SHORT TERM EARTHQUAKE PRECURSOR

      1984, 6(3):35-43.

      Abstract (549) HTML (0) PDF 603.30 K (588) Comment (0) Favorites

      Abstract:Immediately before an earthquake the pressure water layer may produce momentary flow under the action of pulse-shaped earthquake force. In the light of the unsteady flow theory the authors proposed a mechanism to calculate the theoretical curves of the water level drop and the flowing rate of the underground water in the abnormal boreholes according to the radial symmetrical flow model so as to imitate the typical observational curve of the uprising of well water. The developing process of this mechanism requires the formation and vanishing of a funnelshaped distribution of ground water level. Therefore, it is necessary to make further calculations on the theoretical abnormal curves of vertical deformation on the ground surface, gravity, geoelectricity and geomagnetism. These phenomena are all related to the growth and decay of the funnel. Before a strong earthquake, lots of abnormal points of uprising of well water type are generated. At the same time, due to variations of the ground stress and deformation field, the balance state of ground water distribution is disturbed and subsurface fluid flows along faults and crevasses. Thus, geophysical effects more complex than radial symmetrical flow will be produced. This is a shallow layer mechanism of short-term precursors.

    • APPLICATION OF THE TOTAL GEOMAGNETIC INTENSITY DATA IN EARTHQUAKE PREDICTION

      1984, 6(3):44-48.

      Abstract (502) HTML (0) PDF 327.92 K (625) Comment (0) Favorites

      Abstract:In this paper, the total geomagnetic intensity data and the difference of total geomagnetic intensity between two stations were used to eliminate short-term change of geomagnetic field, and at the same time the influence of long-term change was weakened, so that the annual change is a linear change. Based on this, the regional correction value of the residual long-term Change was obtained by the method of trend surface. After processing the data, it was shown that before the great Tangshan earthquake there were. probably anomalies for more than one and a half years, with change amplitude about 10 gels. Within the network of stations, the other earthquakes with magnitude of about 6 were also accompanied by anomalies of total geomagnetic intensity.

    • PREDICTION OF THE JINGHONG EARTHQUAKES IN YUNNAN PROVINCE, CHINA AND THE LAIZHOU EARTHQUAKE (M=7.0) IN THE VIET NAM

      1984, 6(3):49-54.

      Abstract (510) HTML (0) PDF 422.55 K (611) Comment (0) Favorites

      Abstract:In this paper, circumstances and chief basis of medium term, short-term and impending earthquake predictions of the Laizhou earthquake(M=7.0) in June, 1983 and the Jing hong earthquakes (M=5.8, 5.3, 5.7) in Dec. 1982 and May 1983 were provided. The medium term prediction was put forward by the following:Anomalies had emerged in change of releasing speed of ∑√E. The stage in which ∑√E was picking up speed in this area was determined from this. Coming to the conclusion by periodic analytic methods-"Fisher" method et al. was that quickening of the release of ∑√E would last by the end of June, 1983. We determined by migrating regularity of earthquakes that earthquake would take place in the area where is to the south of Jinghong-Jiangcheng, Yunnan province. Bases of Short-term prediction is as following, Three stripe-belt of earthquakes of NE appeared in proper order in seismogenic process. Value of b came down from 1.3 to 0.55. Consulting sudden change of radon content inground water we calculated magnitude of future principal earthquake would be bigger than 6.5. We consulted the general modulation model of the reference[1] and determined place where is earthquake focus was modulated, thus made the impending earthquake prediction of the Laizhou earthquake (M=7.0).

    • A PHOTOELASTIC EXPERIMENT FOR SIMULATING TECTONIC STRESS FIELD IN SEISMIC REGION BEFORE AND AFTER TANGSHAN EARTHQUAKE

      1984, 6(3):55-61.

      Abstract (546) HTML (0) PDF 1.15 M (694) Comment (0) Favorites

      Abstract:The purpose of this paper is to outline a photoelastic experiment with a model for the tectonic stress field of the Tangshan region under a compression in N60°E direction. In the same experiment, the stress release of the strong earthquake was also simulated by using the method of hole-drilling. The results are as follows:
      1. When the Tangshan region was undergoing a compression in N60°E direction, the maximum shear stress was concentrated at the Tangshan-Fengnan district, Yejituo village, Luanxian county and Lulong county. These stress concentration regions were mostly corresponding to the epicentral areas of the Tangshan earthquake(M=7.8), the Luanxian earthquake(M=7.1) and their strong aftershocks. It has been recognized that the occurrences of the Tangshan earthquake and its aftershocks were due to the compressive stress field in nearly EW direction.
      2. Though the stress was released during the Tangshan earthquake (M=7.8), it still increased in those areas when the background value of stress was high before the earthquake event. This shows that a readjustment of the stress field was caused by the Tangshan earthquake, thus intensifying the dynamical conditions for the occurrences of the strong after-shocks.

    • INVESTIGATION OF THE CONDITIONS OF UNDERGROUND MEDIUM ASSOCIATED WITH THE OBSERVATION OF EARTH RESISTIVITY——FIRST PAPER

      1984, 6(3):62-67.

      Abstract (488) HTML (0) PDF 420.18 K (499) Comment (0) Favorites

      Abstract:In this paper the geologic structure under observing station of earth resistivity has been studied. Based on the various data of earth resistivity ρ obtained before the four strong earthquakes (M>7)and some experimental results, the observing cife is supposed to be selected in either side of fault of earthquake foci, not in the broken rock formation.

    • THE DOME-COL STRUCTURE AND ITS RELATION TO EARTHQUAKES AN EXAMPLE FROM WEST HUPEI AND WUHAN

      1984, 6(3):68-76.

      Abstract (476) HTML (0) PDF 719.63 K (566) Comment (0) Favorites

      Abstract:Taking the Dome-Col structure in the West Hupei and Wuhan area as a typical example, a new form of neo-tectonics has been made. The tectonical characteristics, properties, state of stress, and their relation to earthquakes have been analysed preliminaryly.

    • THE COMMON CHARACTERISTICS OF SEISMICITY PATTERN FOR THE TWO EARTHQUAKES AT LIYANG

      1984, 6(3):77-83.

      Abstract (556) HTML (0) PDF 484.50 K (711) Comment (0) Favorites

      Abstract:In this paper, based on the data of foreshocks of two main earthquakes M=5.5, 1974 and M=6.0, 1979 at Liyang, Jiangsu Province the some common have been found in the foreshock seismicity pattern. They are the following:
      (1) These two earthquakes had almost the same duration of foreshocks activity.
      (2) The strong and weak foreshock activities before the two earthquakes occurred alternatively.
      (3) The geometry of the seismic gaps for the two main shock looked same.
      (4) The seismic activities in imminent term showed a band-shaped bistribution.
      (5) There was a bay-shaped quiet area of foreshocks for main shocks in a time-space diagram.
      The reason of characteristics shared by the fore-earthquake piror to the major shock occurring in Liyang mentioned above has been discussed in this paper also. The authors assume that the two earthquakes might have similar broken course under the equivalent stress field and traced back to the process, it is thoughe to be provided with the same condition of both medium and geological structure.
      Finally, these characteristics are of significance in earthquake predication.

    • LAYERED CRUSTAL STRUCTURE IN GANSU REGION

      1984, 6(3):84-91.

      Abstract (465) HTML (0) PDF 531.74 K (376) Comment (0) Favorites

      Abstract:The layered crustal model in Gansu region was obtained based on average synthetic curves of traveling time, which presented more than 2000 initial P and S phases of 143 events, the average model para-meters are follows:
      In addition it is suggested in this paper that most of the earthquakes used in this paper seemed to cluster at the depth of about 7km, where the boundary of two layers of different types of gvanit exists. Finally, the feasibility of average synthetic method has been discussed.

    • RECENT TECTONIC STRESS FIELD OF THE HUBEI PROVINCE AND ITS VICINITY

      1984, 6(3):92-98.

      Abstract (543) HTML (0) PDF 487.75 K (701) Comment (0) Favorites

      Abstract:The composite fault plane solutions for earthquakes in the region of Sanxia, Macheng, Puqi and Danjiang are obtained respectively during the preiod from 1969 to 1981. The result shows that there is no uniform regional recent tectonic stress field in these areas. According to the orientation of the maximum compressive stress, the studied region can be divided approximately into four subregions. The characteristics of the stress field in the region are regarded as a particular phenomenon due to that it is located in the transition zone between Northern, Southern and Western China.

    • SOME SEISMICAL PRECURSORS BEFORE THE 1976 TANGSHAN EARTHQUAKE

      1984, 6(3):99-105.

      Abstract (592) HTML (0) PDF 411.29 K (645) Comment (0) Favorites

      Abstract:The Tangshan earthquake (M=7.8.) of July 28, 1976 is the heaviest disaster in China this century.Many of seismologists are concerned about that whether there were some precursors before this catastrophic earth-quake.For the sake of reviewing the possibity of predicting the Tangshan earthquake, a rich and varied book had been published[1], In this paper we attempt to discuss a precursory earthquake migration and the appearance of the seismic activity zones several years before the Tangshan earthquake.

    • THE SEISMOTECTONIC STRESS FIELD IN THE CHINESE CRATON

      1984, 6(3):106-121.

      Abstract (585) HTML (0) PDF 878.56 K (583) Comment (0) Favorites

      Abstract:The seismotectonic conditions in China are determined by the fact that the Eurasian, the Indian, the Philippine and the pacific tectonic plates extend into its vicinity. The Pacific plate pushes from the NE, the Philip-pine plate from the SE and the Indian plate from the S into the Eurasian plate. The intraplate stresses in China are the continuation of the indicated rim stresses. Evidence for their orientation is based on the statistical assessment of in-situ measurements, earthquake fault plane solutions, valley trends and joint orientations. Inasmuch as the direction of the rim stresses is different in various sectors, their continuation into the plate interior must eventually lead to a stress discontinuity:This is the band of the N-S seismic zone at roughly 104°E longitude. Thus, the latter is seen to be a direct consequence of the plate tectonic conditions prevailing in the vicinity of China.

    • >研究报导
    • A DISCUSSION ON EARTHQUAKE PREDICTION BY MEASURING RAYS IN THE SOIL BY THE ENERGY SPECTROMETER

      1984, 6(3):122-125.

      Abstract (568) HTML (0) PDF 318.50 K (612) Comment (0) Favorites

      Abstract:1980年下半年开始用携带式能谱仪对兰州地区土壤中的γ射线进行定点测量。1981年5月以后,取得了几个月的连续观测资料。测试条件稳定后的数据是可靠的。平时的放射性涨落都在2%以下。图1为1981年5月9日至10月26日6个多月的一段曲线。

    • ON SYNTHETIC PROBABILITY MODEL FOR EARTHQUAKE PREDICTION

      1984, 6(3):126-129.

      Abstract (549) HTML (0) PDF 247.81 K (656) Comment (0) Favorites

      Abstract:本文试图探索在现有各种预报手段的基础上逐渐形成一种比较客观、比较定量的综合预报技术的可能性,並提出一种地震预报的综合概率模式,供地震部门参考,並希望广大地震预报工作者能对这个问题展开讨论。

    • CALIBRATION OF THE SENSITIVITY IN TNE WATERTABLE STRESS CONVERTION BY THE ATMOSPHERE AND THE TORRENTIAL RAIN AND ITS SIGNIFICANCE

      1984, 6(3):130-134.

      Abstract (511) HTML (0) PDF 354.14 K (493) Comment (0) Favorites

      Abstract:随着地下水动态观测工作的开展以及观测仪器的改进,在不少井孔的观测中,观测到了由气压变化、急剧降水引起地下水位的变化现象。此现象一般称为"气压效应"和"暴雨效应"*(1-5)。笔者认为,研究气压效应及暴雨效应有更广泛的意义。例如,应用气压效应及暴雨效应来确定井孔地下水位的应力格值将有助于对井孔地下水位的基本特征的认识,有益于地震预报。

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