• Volume 20,Issue 1,1998 Table of Contents
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    • THE PROPAGATION OF SEISMIC WAVES IN CRACKED TWO-PHASE ANISOTROPIC MEDIUM

      1998, 20(1):1-8.

      Abstract (486) HTML (0) PDF 342.97 K (926) Comment (0) Favorites

      Abstract:Based on the propagation theories of seismic waves in the anisotropic medium and in the cracked two-phase medium separately, the constitutive relations and dynamic equations of the propagation of seismic waves in cracked two-phase anisotropic medium with symmetric axis of 4 rank have been derived. It was pointed that 6 types of quasi-longitudinal and quasi-shear waves may propagate in the cracked two-phase anisotropic medium. They are:QP1(quick longitudinal wave), QP2(slow longitudinal wave), QSV1,QSH1(two splitting quick shear waves) and QSV2,QSH2(two splitting slow shear waves). As an example, the propagation of plane waves was analyzed further.

    • THE BIFURCATION STRUCTURE OF RUNDLE MODE EARTHQUAKE AND ITS EXPLOSION CRITERIA

      1998, 20(1):9-13.

      Abstract (539) HTML (0) PDF 278.37 K (788) Comment (0) Favorites

      Abstract:The nonlinear equation is derived for Rundle mode earthquake and is transformed into the standard Weierstrass equation.On the basis of the bifurcation theory of Weierstrass function we have found,which has been admitted internationally,three phases of the earthquake and the criteria for differentiating them are analysed.And the criteria for the strong earthquake explosion and the occurrence of weak ones are presented respectively.Expressions for the repetition period of weak earthquakes of Rundle mode are given in detail too.This paper is valuable to the earthquake prediction.

    • STUDY ON THE DISTRIBUTION OF THE FIRST MOTION MARK OF P WAVE BY USING THE SEISMIC SOURCE MODEL OF CRACK CONTAINING HYPERPRES SURE GAS

      1998, 20(1):14-20.

      Abstract (540) HTML (0) PDF 345.88 K (829) Comment (0) Favorites

      Abstract:By using the seismic source model of crack containing hyperpressure gas[1],the distribution of the first motion mark of P wave is studied.According to the deduction,the cracks containing hyperpressure gas with different inclination can form the distribution pattern in four quadrants of first motion mark of P wave and the nodal lines of P wave in the shape of conic section,such as circle,ellipse,parabola and double-curve etc..According to the shape of nodal lines of P wave and type of instability,the earthquakes are classified.The distribution feature of first motion amplitude of P and S waves and the feature of ground deformation etc.deduced correspond with practice.

    • A DISCUSSION ON COMMON CHARACTERISTICS BETWEEN VOLCANO AND EARTHQUAKE AND PROBLEMS CONCERNED

      1998, 20(1):21-27.

      Abstract (505) HTML (0) PDF 251.33 K (639) Comment (0) Favorites

      Abstract:Phenomena of volcano and phenomena of earthquake are analysed comparatively.The result shows that there are obvious common characteristics in distribution range,deep structure and other aspects except exterion state between volcano and earthquake.The author considers it is because volcano and earthquake all have relation to magma activity through study and it is possible that earthquake results from magma intrusion in crust directly.

    • THE LATEST QUATERNARY TECTONIC DEFORMATION OF TERRACES OF JIUXI BASIN IN WEST QILIANSHAN MOUNTAINS

      1998, 20(1):28-36.

      Abstract (591) HTML (0) PDF 364.72 K (1010) Comment (0) Favorites

      Abstract:The Jiuxi basin with several kilometers Cenozoic deposits in west Qilianshan mountains is located in the junction of the Tibet, Tarim and Alashan blocks. It is one of the regions which are characterized by strongly active folding and faulting with NW~NWW trend, where surface thrusts, blind thrusts and active folds are the main structural style.Tectonic deformation since early Quaternary has continued to the present time and is confirmed by warped and faulted stream terrace surfaces, and tilted flood deposits.
      When the Shiyouhe river and Baiyanghe river have cut into the cores of the anticlines in the basin, different types and numbers of terraces have developed at different sites. The warping of river terraces demonstrates that anticline growth continues.These features obviously result from the intermittent folding and thrusting of the north Qilianshan fold and thrust wedge since the late Pleistocene.
      Luminescence dating of sediments from these terraces demonstrates that the formation periods of terraces of Shiyouhe, Baiyanghe and Dahuanggou are at about 90, 70, 44, 29, 20, 13 and 5.6 ka B.P. respectively.
      Amplitude and rate of terrace uplift are estimated, which represent the cumulative uplift rates of the fold-and-thrust belts. The uplift rates are larger near by the Qilianshan mountains than far away from it.

    • STUDY ON SYNTHETIC INFORMATION ENTROPY OF MULTI-PRECURSOR OBSERVING DATA

      1998, 20(1):37-41.

      Abstract (582) HTML (0) PDF 269.01 K (839) Comment (0) Favorites

      Abstract:Temporal series of the multi-precursor observing data has been translated into probability temporal series by using the probabilization processing.Based on the work above,the synthetic information entropy of the information source system which is made up of the multi-precursor observing items has been calculated by applying the basic principle of information theory.Calculating the 17 items of precursor observation data in Urumqi and its neighborhood,it has been found that the anomaly process of entropy decrease appeared half a year to one year before moderate and strong earthquakes.

    • PRELIMINARY STUTY ON THE METHOD BUILDING COMPREHENSIVE SEISMIC PRECURSORY FIELD

      1998, 20(1):42-46.

      Abstract (549) HTML (0) PDF 286.36 K (998) Comment (0) Favorites

      Abstract:In this paper,the authors build preliminarily comprehensive precursory field reflecting the time-space evolution of seismic precursors,which is a non-dimensional,normalized and stacking information field.Analysing the process of the time-space evolution of the precursory field in the research area(113°~125°E,32°~44°N),the result shows that the field develops gradually from normally low value scatting to high value confining around the epicenter before the earthquake,and recovers normally after the earthquake.The unique feature of the method is that the analysis on the certain single precursor corresponding to the certain source is avoided,and only analysing the anomalies,location of the focus can be found from the field on the basis of the comprehensive stacking information.

    • THE MERGER OF GEOTHERMAL VORTEXES AND THE TANGSHAN EARTHQUAKE IN 1976

      1998, 20(1):47-50.

      Abstract (539) HTML (0) PDF 250.45 K (1258) Comment (0) Favorites

      Abstract:In this paper,the geothermal vortex action before the Tangshan earthquake in 1976 and relation between it and the Tangshan earthquake are analysed.The results are as the follows:There is a geothermal vortex crowd in north China before the Tangshan earthquake in 1976,which is similar to that before the Xingtai earthquake in 1966.And all geothermal vortexes have merged into great one before the earthquake.This is one of the important event before strong earthquake occurred in north China.

    • RELATIONSHIP BETWEEN INFORMATION AMOUNT OF INTERVAL PROBABILITY OF RATIO BETWEEN NITROGEN AND HELIUM IN WELL LIAOGU-1 AND EARTHQUAKE

      1998, 20(1):51-53.

      Abstract (524) HTML (0) PDF 235.27 K (914) Comment (0) Favorites

      Abstract:In this paper,nonlinear faltung filtering and multiple regression methods are adopted to remove the interference influence in observation data of the ratio between nitrogen and helium.Then the information amount of interval probability of the observation data is calculated.The relationship between the information amount and the earthquakes that are the 1981 Ningjin MS5.8 earthquake and the 1983 Heze MS5.9 earthquake is analysed.It is shown that the high anomalous values of the information amount appeared about two monthes before the two earthquakes.And the information amount returned to normal value after the earthquakes.

    • A DISCUSSION ON ENSEMBLE STABILITY AND LOCAL UNSTABILITY IN JIANG-HUAI SEISMIC AREA AND PREDICTION FOR FUTURE MODERATE EARTHQUAKE

      1998, 20(1):54-58.

      Abstract (495) HTML (0) PDF 285.16 K (786) Comment (0) Favorites

      Abstract:In this paper,the idea of forecasting earthquake with ensemble steady state and regional unsteady state is applied.According to the distribution of historical earthquakes and the seismic tectonic framework,a region (29°~34°30'N,110°~125°E) as a relative independent system in which the seismicity is transient state is chosen.We search the non-linear zone,judge the seismically active tendency and delineate zone which has to be paid close attention to in the future in the region.The results are corresponding with the situation of MS6.1 earthquake in south Yellow Sea occurred on Nov.9,1996.

    • DYNAMIC EVOLUTION CHARACTERISTICS OF GROUND FLUID PRECURSORS BEFORE THE GONGHE MS7.0 EARTHQUAKE 1990 IN QINGHAI PROVINCE

      1998, 20(1):59-64.

      Abstract (517) HTML (0) PDF 221.48 K (691) Comment (0) Favorites

      Abstract:The dynamic evolution characteristics of ground fluid precursors of the MS7.0 Gonghe earthquake on April 26,1990 in Qinghai Province are systematically studied, by using the ground fluid data of 40 observation stations. The results are following:
      (1) The mean deformation rate of faults in seismic belt were synchronous with the cluster anomaly frequency of the ground fluid and the trend anomalies of radon content in groundwater. The curves of the deformation rate of fault and the accumulative frequency of the ground fluid cluster anomalies changed acceleratly in a law of index.
      (2) The acceleration and rising stage of medium-term tendency anomalies of the radon data, which were obtained from the observation stations within 240 kilometers of the focus of the MS7.0 Gonghe earthquake showed transmission feature from the focus to the periphery. The anomalies in short-impending term of the radon data appeared synchronously.
      (3) The ground fluid precursors showed clearly aggravation of fluctuation and hierarchy pattern. It is obvious that the change of daily mean values of fault product gases and flow of groundwater showed three hierarchies with anomalous amplitude which are higher and higher each in the impending earthquake stage.

    • SOME CHARACTERISTICS OF SEISMICITY IN GANSU REGION AND ITS SIGNIFICANCE

      1998, 20(1):65-69.

      Abstract (573) HTML (0) PDF 317.14 K (835) Comment (0) Favorites

      Abstract:About 32 months quasi-periodicity was clearly shown in activity of MS≥3.0 earthquakes in Gansu region.The great shocks with MS≥6.0 in and near the region occurred near the valley of annual frequency curve of MS≥3.0 earthquakes. Since 1980,moderate shocks in Gansu region migrated regularly and steadily in groups from west to east along the northern edge of Qinghai-Xizang block.The migrations show clearly that seismicity in current period has been at a low ebb now,and may enter on a quiet phase in about the year 2002.There will be a seismic activity of MS≥5.5 at about the end of the year 1998 in the Gansu region and its vicinity. That the moderate events of MS≥5.0 occurred at the west end of northern edge of Qinghai-Xizang block is a signal of the beginning of active process of strong moderate earthquakes in Gansu region.

    • ANALYSIS ON CHARACTERISTICS AND MECHANISM OF THE SEISMIC DAMAGE IN LOESS IN YONGDENG MS5.8 EARTHQUAKE REGION, GANSU PROVINCE

      1998, 20(1):70-75.

      Abstract (450) HTML (0) PDF 322.69 K (1061) Comment (0) Favorites

      Abstract:In this paper,the seismic damage phenomena in the loess in Yongdeng MS5.8 earthquake region,Gansu province are collected and analyzed.The damages are divided into two types,one is crisp crash by the quake on the top of the hill,the other is small-scale landslide.For the loess samples from the intensity areas of Ⅶ,Ⅷ degrees,the quantitative analysis on the SEM pictures and the common geo-engineering experiments are carried out.The results show that the loess from this region is full of big pores and is prone to seismic damage when the damp ratio becomes higher.Combining the general knowledge of the field investigation with the indoors experiments data and noticing that just before the earthquake there was a storm,we impute the loess damage to water penetrating on the slope surface and eroding in the slope foot.According to the above analysis,the mechanisms of the two kinds of seismic damage are proposed.

    • THE RENORMALIZATION GROUP METHOD ON SEISMOGENIC BELT RECOGNITION

      1998, 20(1):76-80.

      Abstract (593) HTML (0) PDF 270.46 K (861) Comment (0) Favorites

      Abstract:Based on the study of seismic activity belts,the author introduced the renormalization group method on seismogenic belt recognition,and obtained the theoretical quantitative index of seismogenic belt recognition.Seismic activity belts of 32 earthquakes are analysed and examinated. The results show that 29 belts are seismogenic belts and the other are not the seismogenic belts among the seismic activity belts.The renormalization group method has not only an obvious physical mean,but also rigid predicting recogniting index,which is better suitable for practical distribution of seismic activity belt.So the renormalization group method is a good method for earthquake prediction.

    • INVERSION OF THE PRESENT KINEMATICS CHARACTERISTICS OF FEN WEI FAULT ZONE FROM SEISMIC MOMENT TENSOR

      1998, 20(1):81-84.

      Abstract (547) HTML (0) PDF 231.66 K (882) Comment (0) Favorites

      Abstract:In this paper,the theory and method for inversing the kinematics parameters of a fault zone are discussed,and applying them,the present kinetic characteristics of Fen-wei fault zone are studied.The results show that Fen-wei fault zone extends in the direction of N22°W and is compressed in the direction of N68°E.The mean extending rate is 0.15 mm/a.

    • A DISCUSSION ON THE TIDAL FORCE AS ONE DYNAMIC FORCE OF EARTH EVOLUTION

      1998, 20(1):85-90.

      Abstract (583) HTML (0) PDF 193.86 K (775) Comment (0) Favorites

      Abstract:In this paper,the magnitude and transformation of tidal elastic potential energy and the formation mechanism of internal wave are discussed. In fact,the earth is a non-perfectly elastic body (dissipative body),under action of periodic tidal stress,the dissipation of elastic potential energy on Moho surface will amount to 300 μW/m3 and exceed the output of heat quantity of radioactive matter in granite by a big margin.The chemical boundary surface in the earth such as Moho surface is a density discontinuity one.When some matter on both sides of the boundary is in elasticoplastic state and becomes Maxwell body,alternating loading and unloading shear stress in positive and opposite directions on the rising and falling boundary will be rectified to become one-way loading and unloading shear stress.It will make the matter on both sides directional and reverse movements each other along the boundary surface,forming internal wave.In the course the dissipated tidal elastic potential energy will be transformed into gravitational energy. By using the viewpoint of gravitational divergence,that Moho surface is a chemical boundary surface is discussed.

    • DEEP WELL GEOELECTRICITY ANOMALY IN LINYI STATION BEFORE THE CANGSHAN MS5.2 EARTHQUAKE

      1998, 20(1):91-95.

      Abstract (542) HTML (0) PDF 260.41 K (978) Comment (0) Favorites

      Abstract:Through analysis on deep-well geoelectricity data of Linyi station which is 23 km away from the epicentre of the Cangshan MS5.2 earthquake,it is shown that before the earthquake,the background tendency anomalies of the deep-well resistivity and natural geoelectric potential appeared synchronously with the seismicity anomaly for 5 years.The descending tendency anomaly of deep-well resistivity occurred six months before the earthquake.The natural geoelectric potential and resistivity reduced rapidly 24 days before the earthquake,and then rose again abruptly after the earthquake.

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