• Volume 5,Issue 3,1983 Table of Contents
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    • THE STUDY ABOUT THE NORMAL CHANGES OF RADON CONTENTS IN THE SPRINGS AND DRILL HOLES LOCATED ON THE SOUTH-NORTH SEISMIC BELT

      1983, 5(3):1-10.

      Abstract (551) HTML (0) PDF 798.60 K (765) Comment (0) Favorites

      Abstract:There have been reports on the characteristics of the changes of radon contents in the groundwater before the occurrence of art earthquake so as to predict an earthquake in China and abroad. However, what is their change during the period of no earthquakes? Few reports have been presented so far. In this paper, the materials are mainly from the stations located on the South-North seismic belt. First of all, we study the change shape of the curve of radon contents for a year. Secondly, we analyse its causes of formation. In accordance with what we have mentioned a definition of the normal changes of radon contents in the groundwater is given. It means that during the period of no earthquakes the data of radon contents in the groundwater obtained form observation shown that there are certain regular change shapes for a year and these shapes are similar to each other every year. The pattern of change of radon contents in the groundwater is known as their normal changes. According to the definition, thief normal changes can be divided into three patterns:(1) The radon contents increase in summer but fall in winter; (2) The radon contents fall in summer but increase in winter and; (3) the radon contents are almost a constant for a year. When the norma lchanges of radon contents in a certain spring or a drill hole have been clearly known, and according to thief shapes, it can be inferred what facters which have disturbed the normal changes of radon contents are and then we can judge in time whether they are abnormal or not.

    • THE LABORATORY STUDY ON THE CRACKING STOPPING AND THE DISCUSSION ON THE STOPPING CONDITION OF SEISMIC FRACTURE

      1983, 5(3):11-17.

      Abstract (681) HTML (0) PDF 545.49 K (888) Comment (0) Favorites

      Abstract:Using the theory of stopping crack in the fracture mechanics and experimental results of stopping crack with photoelastic material, the problem about stopping condition of seismic fracture has been discussed. The suitable seismo-geologocal conditions of fracture-stop are suggested. These conditions are (1) the region in which a middling strong earthquake happened not long before (2) the source region in which a large earthquake (Ms≥7)occurred historically (3) the transversal fault and the intersecting region of some faults (4) the massive block and rise. Based upon these conditions, the strength of future strong earthquakes may be estimated-Therefore, it is perhaps of great significance to prediction of the moderate or long-term earthquake.

    • A PRELIMINARY STUDY ON THE DURATION RATIO OF THE CODA WAVE OF LOCAL EARTHQUAKES FOR THE KUERLE 5.8 AND KUCHE 6.0 MAGNITUDE EARTHQUAKES

      1983, 5(3):18-23.

      Abstract (570) HTML (0) PDF 422.99 K (797) Comment (0) Favorites

      Abstract:The ratio between the arithmetic average of two horizontal lomponents and the vertical component of the seismic coda length of local earthquakes is selected as the parameter. We have analysed the seismograms of the 104 local earthquakes occurred before and after 5.8 magnitude main shock on April 22, 1978(during Jan. 1, 1977……Aug. 8, 1978), recorded by 65 type seismograph at Kuerle seismological station, and those of the 128 local earthquakes occurred before and after Kuche 6.0 magnitude main shock on March 29, 1979(during Feb. 1, 1977……June 6, 1979), recorded by BTK type seismograph at Xinyuan seismological station. The duplex maximum noise amplitude(mm)in a few minutes before P wave first motion is selected as the noise belt to determine the ending time of coda wave. The epicentral distance of local earthquakes is △<200 km, magnitude interval is 0.7≤Ms≤4.5. The result shows that a certain low value of τHV at Kuerle seismological station occurred about a month before the Kuerle 5.8 magnitude earthquake while the change of τHV recorded by Xinyuan seismological station, was not so obvious before the Kuche 6.0 magnitude earthquake, although some abnormal display occurred.

    • AN ANALYSIS OF EARTH-RESISTIVITY ANOMALIES OF XIAN STATION

      1983, 5(3):24-29.

      Abstract (570) HTML (0) PDF 478.78 K (803) Comment (0) Favorites

      Abstract:There are many factors which influence the earth-resistivity of Xian station. But the tendency to decrease and the two lowering bow anomalies on the background are the truev arieties of the earth-resistivity in this area. The tendency to decrease is dependent on the cavein of the earth's surface, the creep of the earth's surface crevice and the drop of the level of load-bearing water in Xian area. The two lowering bow anomalies are closely related with reverse varieties of the earth's surface deformation and the accelerative activity of the earth's surface crevice in the area.

    • STUDY ON SHORT TERM TEMPORAL ANOMALY OF RADON CONTENT IN GROUND WATER BEFORE SOME MODERATE AND STRONG EARTHQUAKES

      1983, 5(3):30-35.

      Abstract (473) HTML (0) PDF 468.57 K (738) Comment (0) Favorites

      Abstract:In this paper, according to the analyse of short term temporal anomaly of radon content in ground water for some strong and moderate earthquakes in Gansu and near regions in the last few years, such as Songpan earthquake (Ms=7.2) in Sichuan, Lixian earthquake (Ms=5.0) in Gansu, Haiyuan earthquake (Ms=5.5) in Ningxia and based upon the data of 139 times of the impending earthquake sudden change of radon content in wells for fifty strong and moderate earthquakes collected and analysed, a net work system of setting up observation points with detecting capability of radon content has been proposed. In case the sudden change of impending earthquake of radon content, that is speedy ascending or drop for a short term, takes place at the observation point, it may be regarded as a probable forerunner signal of occurring strong or moderate earthquakes. In accordance with the above-mentioned probable rule, a strongest earthquake (Ms=4.1) in Wuwei, Gansu on June 8, in 1982 had been predicted. The prediction was in conformity with the occurrence of the earthquake in time, magnitude and place.

    • A PRESEISMIC DECREASE VARIATION OF THE GEOMAGNETIC VERTICAL COMPONENT AHE TND DISCUSSION ABOUT ITS CAUSE

      1983, 5(3):36-42.

      Abstract (426) HTML (0) PDF 615.38 K (747) Comment (0) Favorites

      Abstract:In this paper, the geomagnetic variations on the earthquake of magnitude Ms7.8 occurred near Tangshan on July 28, 1976, and the earthquake of magnitude Ms5.5 occurred near Haiyuan were analysed. Then it is pointed out that the preseismic decrease variation of the geomagnetic vertical component may be a characteristic of the seismomagnetic warning sign of the earthquake occurred near the high electrical conductivity area. Meanwhile it is suggested that this geomagnetic variation may be caused by the change of the Curies constant temperature surface caused by the underground medium convection.

    • THE CHARACTERISTIC ANALYSIS OF ATMOSPHERE PRESSURE FIELD BEFORE STRONG EARTHQUAKES IN NORTH CHINA

      1983, 5(3):43-47.

      Abstract (554) HTML (0) PDF 363.04 K (773) Comment (0) Favorites

      Abstract:In this paper, the relationship between atmosphere pressure and the four strong earthquakes occurring in north China(i. e. Xingtai, Bohai, Haicheng and Tangshan)have been studied. And it is found that the pressure change patterns in space and time before four earthquakes are much the same as follows:
      1. The departure values of the monthly mean pressure in epicentral districts before earthquakes are evidently different from those of the surrounding ones. The epicenter is very close to the centre of pressure departure.
      2. The values of the daily mean pressure in epicentral districts before earthquakes show a special larger change which is usually beyond 10 mb.
      The above-mentioned phenomena illustrate that it is possible to have the influence of the seismic brewing process on atmosphere and the existance of trigger action.
      The author thinks that these consequences can be applied to the short-term prediction.

    • THE STRESS FIELD OF EARTHQUAKE SOURCE AND THE TECTONIC STRESS FIELD

      1983, 5(3):48-56.

      Abstract (500) HTML (0) PDF 709.35 K (939) Comment (0) Favorites

      Abstract:Some of the stress fields obtained from earthquake mechanism according to double couple model of earthquake represent tectonic stress field, but some of them represent the transformed stress field. The axes P, B, and T obtained from earthquake mechanism correspond with the maxmum, intermediate and minimum principal axes of the tectonic stess respectively if the earthquake was caused by stick-slip mechanism on an acting fault, though there may be a departure from the real directions. The transformed stress field was analysed when blocks of the crust moved relatively. The axes P, B, and T are entirely different from the principal axes of the tectonic stress if the earthquake was caused by transformation stress field. Through analysing several earthquake sequences, it was shown that uniform stress field was obtained from earthquake mechanism when the transformation stress field was taken into account. Therefore, to obtain the tectonic stress field from an earthquake mechanism, it must be clarified that the earthquake was caused by stick-slip or shear fracture due to tectonic stress or caused by conjugate shear fracture due to transformation stress some criteria were given. The tectonic stress could be obtained directly from the former, but some transformations have to be done if the tectonic stress was obtained from the latter.

    • THE CONDITION IN THE DEPTH OF XIANSHUIHE FRACTURE BELT AND RELATIONSHIP BETWEEN IT AND EARTHQUAKES

      1983, 5(3):57-62.

      Abstract (509) HTML (0) PDF 553.31 K (728) Comment (0) Favorites

      Abstract:On the basis of data on the gravity, the aeromagnetic survey, the apparent crustal thickness, the seismicity and the depth of focus, the author preliminarily studied and discussed the condition of formation of the Xianshuihe fracture and relationship between it and occurrence of earthquakes. Results were showed as follows:
      1. As there was no clear and direct reflection of the Xianshuihe fracture on boundary surface between the crust and the mantle at the top of the mantle, this fracture may not pass through the lithosphere and was a strong regional fracture inside the crust.
      2. This fracture had developed on the tectonic background of upheaval of the crust before the Variscian period.
      3. It will be seen on the section of the crust that the belt between the bottom of metamorphic rock of the Palaeozoic era and magnetic Curie isothermal surface is place of occurrence and brewing of earthquakes of the fracture belt.
      4. Because of irruption of magmas or fluids with high temperature, upheaval and higher temperature sites on magnetic Curie isothermal surface usually are the bottom of fractures brewing earthquake. Because temperature of the bottom is raised and the upside is caught here, the stress is concentrated easily and movement of the fracture easily is caused, therefore it is principal place where strong earthquakes brew and occur.

    • INFLUENCE OF ATMOSPHERIC PRESSURE UPON QUARTZ GRAVIMETER

      1983, 5(3):63-70.

      Abstract (557) HTML (0) PDF 652.08 K (677) Comment (0) Favorites

      Abstract:The gravimeter's quartz system is in air-tight sealea cases, used to be considered no pressure effects.
      The present experiment with 8 quartz gravimeter(2 Scientrex CG-2, 3 ZSM-3, 3 Worden)indicate that there is significant reletivity between the pressure variation and the reading of gravimeters, but the gravimeters have different regression coefficients. It is necessary to correct the pressure effect from gravity measurement result.
      The authors wonder if there is a better method than calibrating gravimeters by gravity difference caused by altitude difference.

    • ON THE DARI EARTHQUAKE OF 1947 IN QINGHAI PROVINCE

      1983, 5(3):71-77.

      Abstract (766) HTML (0) PDF 1.21 M (604) Comment (0) Favorites

      Abstract:On March 17,1947, an earthquake of magnitude 7(3)/(4) occurred in the Dari area of Qinghai province. The epicentre was in the North border district of the Bayankalashan Mountain range. The intensity of the epicentre area is X. The direction of the long axis of the equiseismic line was N 50°W.The deformation band of the Dari earthquake was 150 km long. It consisted of a series of fault scarps, little upheavals, little segs and fissures and fractures. Having analysed characteristics of deformation band and composite laws of various deformation phenomena, the author judged that the direction of major compressional stress of earthquake province is NEE-SWW.
      The trend and distribution of deformation band of this earthquake was in conformity with the Richa-keshoutan fractures of N50°W and fractures of NNW. Therefore, the cause of occurrence of this earthquake was the result of movement of the Richa-keshoutan fractures and NNW fracture, which still continues at present.

    • NEOTECTONIC SYSTEMS IN SICHUAN PROVINCE AND THEIR EVOLUTIONS

      1983, 5(3):78-86.

      Abstract (552) HTML (0) PDF 768.73 K (685) Comment (0) Favorites

      Abstract:The most intense neotectonic activities in Sichuan province occurred at least three times in the history. The first episode occurred during the time between Eogene and Neogene, the second between Neogene and early Pleistocene and, the third between early Pleistocene and middle Pleistocene. They control the activities of various types of structural zones and structural systems respectively, and through complex evolutions they finally take complicated forms of structural contours and mountains and rivers. The structural patterns formed in Neiod are as follows:east-west structural zone, north-south structural zone, chess-board structures, Neocahaysian system, Qinghai-Xizang system, rotational shear structures and so on. The structural stress fields and their trasitional models reflected by the generations and evolutions of all the structural zones and their genetic sequences occurred with good regularity. As a whole, the north-south trending compression was earlier than the east-west trending compression. Active structures occur within Sichuan province from middle pleistocene up to present with north-south trending compression fractures and the related large-seale chess-board structures composed of north-east and northwest trending fractures as the main part and, with folded fractures in western Sichuan province of Neocathaysian system and Qinghai-Xizang system as the secondary part, it is of instructive significance to select the active structures to the study of seismogeology and engineering geology.

    • MEETING OF A PROPAGATING SHEAR FRACTURE WITH A STATIC FAULT

      1983, 5(3):87-90.

      Abstract (556) HTML (0) PDF 268.94 K (567) Comment (0) Favorites

      Abstract:In the study of physics of earthquake source,the meeting of a propagating shear fracture with a static fault is an important problem. It is related to stopping of propagation of fracture, anomalous seismic intensity and so on.This paper briefly discusses the problem.

    • THE CHARACTERISTICS OF THE MODERATE-SMALL EARTHQUAKE CONCENTRATION BEFORE STRONG EARTHOUAKES IN AND AROUND NORTH CHINA

      1983, 5(3):91-102.

      Abstract (577) HTML (0) PDF 724.78 K (795) Comment (0) Favorites

      Abstract:As the reliability of seismicity data is the highest in all "earthquake prediction data",more and more seismologists are thinking of finding the useful and practical precursors among the data of seismic activity which may be large or small and their centres may be near or far from the epicentre of the strong earthquake[1-5]. According to the present scientific and technical level, the work of this study is one of the principal ways to investigate earthquake prediction.Since 1970, the ability to observe the small earthquakes in and around north China is increasing gradually (5), so that the data observed in the different parts of north China are more comparable.In this paper, using the data of the seismicity we will discuss the anomalous phenomena appeared during the process of regional quick fracture in north china and find the information of strong earthquake risk place (or area).

    • >短文
    • GEOGRAPHCAL DISTRIBUTION OF EARTHQUAKE MAGNITUDE DEVIATION OF SURFACE WAVE OF LANZHOU SEISMIC STATION

      1983, 5(3):103-106.

      Abstract (579) HTML (0) PDF 351.37 K (592) Comment (0) Favorites

      Abstract:自从1935年里克特提出震级标度以后,地震界才对地震强度有了较为客观、定量的微观描述。然而近二、三十年来,震级精度提高得並不快。这就给整个地震研究工作带来了不便。

    • THE PHENOMENA OF VERTICAL MOVEMENT IN EARTHQUAKE AREA

      1983, 5(3):107-110.

      Abstract (567) HTML (0) PDF 416.73 K (484) Comment (0) Favorites

      Abstract:我国是一个多地震的国家,有历史记载以来发生了许多次强烈破坏性地震。这些地震究竟是什么力量引起的,目前一般认为是由于太平洋板块和印度板块对我国大陆挤压作用的结果。

    • ON THE ANOMALY OF SOIL LAYER STRESS IN EARTH'S CRUST IN TIANSHUI AREA OF GANSU PROVINCE

      1983, 5(3):111-114.

      Abstract (532) HTML (0) PDF 368.50 K (448) Comment (0) Favorites

      Abstract:测量土层中的应力或应变变化,以获取地震的前兆信息,为地震预报服务,这种方法应用已久。在一些大震之前土应力往往有明显的变化。甘肃天水地应力站所观测到的土应力变化曲线即是一例。

    • >简讯
    • THE SYMPOSIUM ON THE EARTHQUAKE TENDENCY IN THE PERIPHERY AREA OF EERDUOSI MASSIF WAS HELD IN XIAN OF SHANXI PROVINCE

      1983, 5(3):115-115.

      Abstract (450) HTML (0) PDF 87.18 K (512) Comment (0) Favorites

      Abstract:经兰州地震研究所和陕西省地震局共同发起,在有关省(区)地震部门大力协作下,鄂尔多斯地块周缘震情趋势讨论会于1983年5月26日至30日在西安召开。参加会议的有陕西、甘肃、宁夏、内蒙、山西等省(区)地震部门的代表以及国家地震局地质所、第二测量队、青海省地震局、西北工业大学、陕西师大、西安市地办等单位的代表共35人。

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