• Volume 3,Issue 1,1981 Table of Contents
    Select All
    Display Type: |
    • EXPERIMENTAL STUDY ON THE VARIATIONS IN APPARENT RESISTIVITY ASSOCIATED WITH THE STRESS-STRAIN STATE OF THE ROCK-WALLS IN THE UNDERGROUND MINE TUNNELS

      1981, 3(1):1-24.

      Abstract (555) HTML (0) PDF 1.29 M (789) Comment (0) Favorites

      Abstract:Experiments on the variations in apparent resistivity in the rock walls of the underground mine tunnels had been made for more them two years, meanwhile the stress-strain state of the walls was changing with adjoining tunnels being dug.
      This papev presents and analyses the obtained data in detail, which include those of stress, strain, apparent resistivity, and so on, The mechanism on variations of apparent resistivity and the problem about the directins of extreme values of the variations are discussed briefly.

    • SOME ANOMALIES OF THE SHALLOW ZONE MECHANISM DURING THE IMPENDING EARTHQUAKE

      1981, 3(1):25-31.

      Abstract (542) HTML (0) PDF 571.34 K (769) Comment (0) Favorites

      Abstract:The short-term imminent precursors happened before many severe earthquakes in China may are summarized as follows:
      1. The anomolies progressively migrated towards the epicenter from the outer boundaries.
      2. The amplitudes of the anomolies alternatively fluctuated from high to low as they migrated to wards the epicenter.
      These two points mentioned above, have the significance of predicting the earthquake immediately before it takes place, because they are very easy to be discovered.
      Presented here are the mechanism of the short-term imminent earthquake precursors on the underground water, the animal, the geoelectricity, the earth light, the earth gas, etc, and that of the precursor phenomena on the rmall earthquake actions, the ground deformation, etc——"hydraulic fracturing" mechanism.Before the earthquake, the underground "hydraulic fracturing" phenomena had been indirectly proved by the fact that the levels of the oil in the oil wells and of the water in the deep wells enormously raise mously (differently from decades to thousands of metcrs) immediately before the earthquake. We suppose that the shortterm imminent anomlies are directiy under the influence of the shallow zone mechanism sather than the control of the seismic source.
      Before the earthquake, the inerease of underground stress and the way of increase, the closed degree of the underground reservoir aquifer body can be regarded as the causes hwv the pore pressure ncreased up to "breakdown pressure". As the hydraulic fracturing phenomenon suddenly occurred and suddenly disppeared, the precursors Caused by it are in general, jumpy too.
      Many coseismic phenomena and the anomolies after earthquakes Can also be cxplained by the theory of the "hydraulic fracturing" mechanism.

    • ANOMALOUS VARIATIONS OF THE CHARACTERITICS OF SEISMIC WAVES BEFORE THE TANGSHAN(唐山) STRONG EARTHQUAKE(M=7.8)

      1981, 3(1):32-40.

      Abstract (560) HTML (0) PDF 601.70 K (499) Comment (0) Favorites

      Abstract:This paper deals with the premonitory anomalies of some kinematical and dynamical characteristics of seismic waves,i.e.the seismic velocity anomalies and the anomalies of the amplitude ratio of s and p waves before the Tangshan (唐山) strong earthquake (M=7.8) on July 28,1976.By means of three different methods the temporal and spatial variations of the mean seismic vilocity ratio vp/vs,the curvature coefficient of the Wadati diagram β and the mean longitudinal wave velocity vp in this region since 1970 have been researched respectively.At the same time the premonitory anomalous variations of the amplitude relation of the vertical maximum displacements of s and p waves recorded by two groups of seismograph stations have been investigated.
      The results obtained form the preliminary study show that:(1) The anomalous variations of the vp/vs,β,vp and As/Ap in this area were very remakable before the Tangshan (唐山)strong earthquake (M=7.8);(2) the characteristics of the vp/vs,β and vp anomalies are similay to those of the corresponding anomalies before some other strong earthquakes in China;(3) the Ap/As anomaly corresponds with the velocity anomaly in the general tendency,but its concrete characteristics depends on the directions of the groups of seismograph stations.
      Finally,the results obtained in this paper are compared with some other results published about the precursors of Tangshan (唐山) earth quake and a brief discussion has been made also.

    • THE PROCESSES OF THE ELASFIC RUPTURE IN THE EARTH'S CRUST AND BIG EARTHQUAKES

      1981, 3(1):41-53.

      Abstract (491) HTML (0) PDF 880.02 K (827) Comment (0) Favorites

      Abstract:In this paper, the process of the present deformation and rupture in the inhomogeneous earth's crust, the system of precursors and the precursor of the rupture, the zones of the strong seismic ruptures and the nefworks of ruptures in the crust of China's continent have been discussed. It has been believed that a process of a big eacthquake, which is not insulary, is a part of the system of quick rupture of tectonic activity from which a large a mount of elastic energy is veleased, The frame of the network of strong seismic ruptures mostly depends on the inhomogeneous strength of the earth's crust. But the form, major direction and the tendency of regional rupture mostly depend on the variety of field stresses. Thus, the seismlc activity and precursors should possess the properties of the network and system. The study of these problems is of great signifcame to the analysis of seismic activilies and precursors.

    • A STUDY OF THE CHARACTERISTICS IN MAJOR-AFTER SHOCK TYPE BASED ON ENERGY AND GEOLOGICAL CONDITIONS.

      1981, 3(1):54-60.

      Abstract (564) HTML (0) PDF 442.71 K (788) Comment (0) Favorites

      Abstract:Generally Speaking, there are three types in the seismic activities. One of them is usually the type of major-after shock. They are related to
      (1) The mode and the rate of the force;
      (2) The physical characteristics of the rocklayer and the geological conditions in the focus region.
      In this papcr we have discussed the characteristics from the viewpoint of energy ang based on geological conditions. It shows that the major-after shock activities usually occur in the second order tectonics connected with the major-fault.
      The volume of the aftershock may be regarded as a region which has been deformed. The product of the critical value of the strain energy per unit volume in the rock and the after-shock volume is in the same order as the energy released by the major-shock.
      We may calculate the strain value of the fracture from the strain energy pcr unit volume.
      It is smaller than the value based on geodesy.

    • THE CHARACTERISTICS OF GROUND MICROTREMORS IN LANZHOU

      1981, 3(1):61-71.

      Abstract (480) HTML (0) PDF 722.79 K (543) Comment (0) Favorites

      Abstract:In order to realize microregionation of the site conditions in Lanzhou, the observation of ground microtremors was carried out in 75 points within this city.
      It is shown that the characteristics of ground microtremors are obviously regional. The Fourier spectra of different, points in Lanzhou are more or less alike with each other. The pikes of the majority of the Fourier spectra occur at 0.3-0.45 sec. But in different areas of Lanzhou there are some various characteristics in the spectra and according to the appearance of the spectra it is able to divide the whole area of this city into 5 regions. So it can be imagined that the characteristics of ground microtremors are dependent on the total natural conditions over the whole region rather than on the local subsoil conditions.
      The maximum amplitude of the ground microtremors at 9-11 in the morning is 0.5-1.5μ. The maximum amplitude of ground microtremors is obviously dependent on the thickness of the soft ground, such, as leoss, loam, silt ect.. The thicker the stratum of the soft ground, the greater the maximum amplitude of microtremors.
      The results of microtremors measurement can be used in the micro regionation of site conditions.

    • THEORERICAL COMPUTATION OF GROUND SEISIC RESPONSE

      1981, 3(1):72-81.

      Abstract (700) HTML (0) PDF 552.75 K (672) Comment (0) Favorites

      Abstract:On the basis of horizontal assumption, the building site with mnlti-layer soil is regarded as a layered soil column of an unit cross section and is simplified as the sherebeam computing model of the lumped-mass. Taking account of the non-linear characteristics of soils, we have used the method of stable wilson-θ to compute the seismic response of every layer soil from base rock to ground. Finally, it is pointed out that this paper is of some significance in engineering.

    • PRACTICE AND APPLICATION OF THE CONGLOMERATED LUMPS CONSTRUTION THEORY

      1981, 3(1):82-91.

      Abstract (549) HTML (0) PDF 804.15 K (792) Comment (0) Favorites

      Abstract:In the present paper it is first of all believed that the essential reason of conglomerated lumps construction is due to both the mass full of uranium after being conglomerated lumps whit ascended to the top of the mantle from the earth kernel and at the same time the mass mixed with rich iron conglomerated into lumps, descended while downwards even ceaselessly into the centres.
      In the world there are nine conglomerated lumps, namely, the Pacific Ocean Asia the North America the south Pole continent Europe, The Sonth America, Africa, the Indian Qcean and the Arctic Qcean.
      In the end the author has made an attempts to explain the guertions concerning the great earth construction, especially the earthquake, in the light of the conglomerated lumps construction theory.

    • PRELIMINARY ANALYSIS OF THE EARTHQUAKE'S DEFORMATION ZONES AND STRUCTURAL BACKDROP IN THE 1932 CHANG MA EARTHQUAKE (M=7.5)

      1981, 3(1):92-100.

      Abstract (532) HTML (0) PDF 636.63 K (657) Comment (0) Favorites

      Abstract:The Chang Ma earthguake (M=7.5) Qccurred on December 25th, 1932 was the conseguence of the then strong movement in western Chang Ma-EBo fault zone. In this zone, the movement of the vertical displacement was more evident in its western sector than the eastern one. Since the Quaternary, the movement had shown in the way of two planes of shear fracture of the north-north west and north-west west.
      The earthguake's deformation zohe expended in the direction of the planes of shear fracture. It appeared in the shape of reversed S on the plane. The north north-west deformation zone indicated a clockwise twist, while the north-west west deformation an anti-clockwise twist. This not only coinsides with the direction of the plane of shear fracture, but also conforms in the direction of twist, compared, with the two planes of shear fracture of the earthquake fault. In Gansu Corridor, when the total structure became the shape of reversed S, while the individual was not, it was one of the geological marks of the western Qi-Lü epsilon structural system that moved recently and at present.
      According to the differentiation in the earthquake deformation zono at the time of the earthquake the direction of the principal compression stress was north 30°-40° east, it was similar to north 33° east, obtained by stress relief method.
      Based on the geological analogical method, it is believed that since the Min Le area and Chang Ma area have similar Comditions in structure and rock, there exists the possibility of middle-strong earthquake.

    • STRESS FIELD AND ITS RELATION TO SEISMISITY IN NORTH CHINA

      1981, 3(1):101-111.

      Abstract (524) HTML (0) PDF 876.69 K (960) Comment (0) Favorites

      Abstract:North China is delineated here by a geological block roughly from 30° to 42° north latitudes and from 105° east longitudes toward east up to sea area. The data of focal mechanisms, geodetic results, ground fractures during earthquakes, isoseismals and new tectogenesis were gathered and analysed. The conclusion that the basic stress field in the crust of North China is quite consistent with compressional axis in the northeast-east direction and tensil in the north-northwest direction and these axes are nearly horizontal was drawn. The relation between the stress field and the medium defines the crustal movement. One of results of the movement is the occurrence of earthquake. From this point of view, the general features of seismisity of North China was discussed. The high and low-tides, the alternately, concentrative activities in various areas, the regular orientations of fault planes and the regular migrations of epicenters appeared in the seismic activity. They are useful for the long-term earthquake prediction.
      The general features of seismogenic process for a great earthquake has been discussed combining with the various phenomena appeared before the Tangshan Earthquake. There were no foreshocks for the most of M ≥ 6 earthquakes of North China. It seems that the long period movement or creep is probably a more universal basis of precursors. On the basis of this some suggestions concerning the future work have been proposed.

    • A STUDY ON THE REASONABLE DISTRIBUTION OF THE REGIONAL SEISMOLOGICAL STATION NET

      1981, 3(1):112-117.

      Abstract (511) HTML (0) PDF 416.41 K (538) Comment (0) Favorites

      Abstract:In this paper the reasonable distridution of the regional station net has been discussed in view of furnishing with seismographs, and the results have been obtained as follows:
      (1) If each station of the network, in which the distance between neigboring stations is about 50 kilometres, is furnished with four visible short period recording seismographs (V0=1.0×105, 1.5×104, 2.5×103, 4.0×102, and if at the same time, several stations, the distance bet ween which is less than 200 kilometres, are furnished with one moderately strong-motion seismograph of V0=50 each, the hypocentres of the earthquakes with magnitude over 1 (Ms ≥ 1) within the network may be determined.
      (2)If the distance between neigboring stations is less than 150 kilometres and all of them have been furnished with the above-mentioned instruments, the hypocentres of the earthquakes with Ms ≥ 1.5 maybe determined.
      On the basis of the above-mentioned results and the present station conditions in Gansu province, the project of the reasonable distribution of the station nets in Gansu has been is suggested. According to this project, in the station net of the east region of Gansu, the hypocentres of the earthquakes with Ms ≥ 1.5 can be probably determined, but in the Gansu Corridor (the western part of Gansu), the hypocentres of the earthquakes with Ms ≥ 2.0 which occur along the long corridor zone in the east region to Jaryuguan (嘉峪关) can be determined probably.

Current Issue


Volume , No.

Table of Contents

Archive

Volume

Issue

Most Read

Most Cited

Most Downloaded