• Volume 7,Issue 4,1985 Table of Contents
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    • INTERPRETATION TO THE OBSERVATIONAL DATA OF NETWORK OF SEISMIC STATIONS IN GANSU, QINGHAI AND NINGXIA FOR A SERIES OF EXPLOSIONS IN YONGDENG COUNTY AND CRUSTAL STRUCTURE OF THE REGION

      1985, 7(4):1-10.

      Abstract (461) HTML (0) PDF 668.39 K (912) Comment (0) Favorites

      Abstract:A series of artificial explosions was made from 1982 to 1983 in Yongdeng County, Gansu Province. This paper deals with the data recorded by the stations in Gansu Province, Qinghai Province and Ningxia Hui Autonomous Region. The velocity of every kind of waves is calculated here: Vpg6.00km/sec, Vsg=3.56km/esc, pn=8.16km/sec, Vsn=4.54kg/sec. The velocity of surface longitudinal wave reaches Vo=4.82km/sec. The reflection wave Pm on Moho discontinuity in 104-180km is 7-10 times greater than Pg wave. The thickness of crust in this region is also gained: 1) Hoxibao-Gaotai, in Gansu, about 48.3km; Gulang-Zhangye-Jiayuguan Pass, 50.2km; the piedmont of Qilianshan Mountain, 53.6km. 2) The middle part and south of Qinghai, 54.4km; 3) Lixian-Wudu, in the east of Gansu, 48.7km. Dingxi-Minxian-Tongwei, 50.5km. 4) Lioupanshan Mountain region, in Ningxia, 51.6km; Jingning, in the west of Lioupanshan Mountain, 48.6 km; Pingliang, in the east of Lioupanshan Mountain, 47.5km; and Baoji, in the southeast of the mountain, 46.1km. It is clear that there is a descend in the edge of northeast of Qinghai-Xizang plateau, by the distribution of crustal thickness mentioned above, but a fluctuation in the eastern area of Gansu Province.

    • A METHOD OF MEASURING PRESSURE BY CONTINUOUS AND AUTOMATIC RECORDING IN DEEP AND CLOSE OIL WELLS AND ITS USES IN EARTHQUAKE PREDICTION

      1985, 7(4):11-19.

      Abstract (445) HTML (0) PDF 607.85 K (658) Comment (0) Favorites

      Abstract:This paper emphatically introduces a method of measuring pressure by continuous and automatic recording in deep and close oil wells and its uses in earthquake prediction. It concretely discussed the condition of observation wells, instruments and materials recorded, it points out that the method has a lot of advantages as compared with others of observing seismic precursors. In accordance with obvious record anomaly of short-period and prequake variation, it is said that the method will be quite hopeful in short-period and prequake prediction.

    • GEOSOUND FEATURES IN SEVERAL REGIONS AND THEIR POSSIBILITY FOR PRECURSOR OF EARTHQUAKE

      1985, 7(4):20-27.

      Abstract (503) HTML (0) PDF 478.68 K (496) Comment (0) Favorites

      Abstract:The geosound observation data collected in this paper consist of Lulong and Changlishire, Hebei Province, City of Yingkou, Liaoning Province, City of Chengdu, Sichuan Province; Juxianshire, Shandong Province and Jiexiushire, Shanxi Province.The spectrum and other features of geosound have been obtained by analysis and processing of the data. At last the mechanism of sound source and the possibility regarded as a precursor of earthquake have been discussed briefly.

    • The Discussion on the relation Between the Changes of Transfunctions with Time and the Seismoactivity near Hexibao

      1985, 7(4):28-35.

      Abstract (416) HTML (0) PDF 541.85 K (700) Comment (0) Favorites

      Abstract:In this paper, relation between the transfunction at Hexibao and the seismoactivity of magnitude Ms above 4.0 within 200 km during the period from 1980 to April 1984 were analysed. The results suggested that the transfunction A generally be about 1.8 and B be 0.02 more of less during the period without earthquake. But before the earthquakes A decreases by about 0.05 and B increases by 0.1 more or less.
      Meanwhile it is pointed that there were seasonal changes in both A anb B at Hexibao. A is less in summer than in winter, but B is more in summer than in winter. It is more obvious after deducting seasonal changes from A and B respectively than that without deducting such changes.

    • THE SEISMICITY AND CHARACTERISTICS OF STRUCTURE STRESS FIELD IN WESTERN SICHUAN, CHINA

      1985, 7(4):36-45.

      Abstract (492) HTML (0) PDF 669.70 K (792) Comment (0) Favorites

      Abstract:The investigation for the change of structure stressfield of the crust is one of the important approaches to earthquake prediction. The data analysis on the enlarged tests of a stress-strain observation system of resistance type has shown that in western Sichuan the change in this structure stress field always takes place with time and space.
      The repeated alteration of the following factors are the immediate reason why the strong earthquakes prepare and occur one by one in this area. They are: accumulation intensifcation, relase and reversion. Luding seismic station had found that before Daofu earthquake of M=6.9 on January 24th, 1981, the direction of the compressive principal stress in the structure stress field had a deflection, near to 90° which lasted 36 days. Stress direction returned to normal 9 days before the earthquake. It has been observed that in western Sichuan, the structure stress field has been in a relatively steady state since Ganzi earthquake of M=6.0 on June 16th, 1982 but in the south it is in an increasing activity, As a result, this new kind of property leads the west of Sichuan to a calm part. but as for the western and northeastern parts of Yannan and fracture zones in Yuanjiang and Honghe are more active and were once hit by strong and moderate earthquakes from 1982 to 1983.

    • THE STUDY OF MULTILAYER-MEDIA BENEATH THE RECORDING STATIONS AT ZHUNGEER BASIN EDGE IN XINGJIANG REGION BY MEANS OF TELESEISMIC P WAVEFORMS

      1985, 7(4):46-58.

      Abstract (439) HTML (0) PDF 759.63 K (768) Comment (0) Favorites

      Abstract:In this paper, we propose a method for the study of crust and upper mantle structure beneath the seismic recording station at Zhungeer Basin edge in Xingjiang Region. The delta matrix of separational form is recomposed by basic propagation term of wave field, resulting in a simplier computational process for the synthetic seismograms of teleseismic P wave.
      Using ten teleseismic P waveforms recorded by the short-period seis mographs at stations, Aleitai, Fuyun, Kelamayi, Ganhezi and Urumqi in this basin edge, we have obtained the synthetic P waveforms in good agreement with observed P waveforms by gradually adjusting the crust and upper mantle model. Our results show that the crust of Zhungeer Basin is of multilayers; the crustal thickness is 52-60 kin, with a low velocity layer in the middle of the crust. The Qα values for this basin are within the normal range of the Eurasian continent, It indicates the attenuation for seismic wave through this region is not very strong.

    • THE EARTHQUAKE FILLING OF INTERPLATES AND THE TYPES OF FAULT MOTION

      1985, 7(4):59-68.

      Abstract (516) HTML (0) PDF 699.33 K (968) Comment (0) Favorites

      Abstract:In accordance with the knowledge of earthquake packing in the edges of plate, an analysis is made in this article, by means of empirical formula about magnitude and the length of fault, on the relation between the geological structure and the earthquake activities in these fracture zones: Tancheng-Lujiang, Zhangjiakou-Yantai, Xianshuihe and the northern edge of Tarim Basin. It is pointed out that inside plates, there also exists such a phenoninon that earthquakes can always be filled and packed along the fracture zones. This kind of earthquake filling and packing is mainly on the zones of torque-compression type and shear slip type. A continuous active fracture zone is on imperative geological condition for earthquake filling inside plates.
      The authors propose that there is very close relation between the earthquake filling and the defferent type(or state)of modern fault motion. The progress in which an active fault develops from stable sliding and relative close and lock to rupture and displacement, is just. the process in which gap of earthquake forms, develops and even a great earthquake begins. What is corresponded with this is the segment of stress accumulahion, locked and release. In geology, the difference between them is: new sediment cover on fault is less and less in order; the bond strength of gouge decreases but its thickness increases. So, a special attention must be paid to those active faults with more new sediment on them, which have been activized since Holocene.

    • THE TOPOGRAPHIC EFFECTS ON MAGNETOTELLURIC RESPONSE

      1985, 7(4):69-78.

      Abstract (520) HTML (0) PDF 540.28 K (633) Comment (0) Favorites

      Abstract:This paper discusses the topographic effects on magnetotelluric response. The authors hcre calculated several magnetotelluric response curves on different topography with finite e ement method, using quadratic triangular element. In the case of Ex-polarization, the effects occur only on the frequency band in which the length of wave propagated under ground is comparable with the amplitude of undulation of topography. In the case of Hx-polarization, the topographic effects are severer than that in Ex-polarization, and it becomes stable as the period increases. The effects are severer on convex place than on concave place. More

    • PRELIMINARY ANALYSIS ON TENTATIVE SURVEY DATA OF HORIZONTAL PENDULUMS IN ANNING AIR-RAID SHELTER, LANZHOU

      1985, 7(4):79-86.

      Abstract (514) HTML (0) PDF 475.85 K (525) Comment (0) Favorites

      Abstract:Anning Tidal Station of Lanzhou(will be built up)is located in an air-raid shelter of Anning, Lanzhou. A group of tiltmeter observation from Seismological Observatory of Lanzhou made a tentative survey during June of 1982 to May of 1983 and had got a series of data. This articlesimply introduces the basic condition of the station and the disturbance factors around that may influence the observation. It also made a preliminary analysis about the tidal data (June through Dec. 1982) and obtained some useful conclusions.

    • VOLUMETRIC CHANGES IN ROCK SUBJECTED TO DIFFERENT STRESS PATHS

      1985, 7(4):87-93.

      Abstract (516) HTML (0) PDF 394.37 K (366) Comment (0) Favorites

      Abstract:The volumetric changes in Jinan gabbro and Changping granite subject ed to three different stress paths have been studied. In all cases the rockwas first loaded to a pre-determined stress state below that which would be conducive to fracture. This was then followed by three different cases of loading. Case A: The maximum principal stress was continuously increased to induce fracture. Case B: The minimum principal stress was decreased to induce fracture. Case C. The minimum principal stress was increased to prevent fracture. The experiments showed that for the same rock dilatant behaviour was different along different stress paths. When compared with the dilatant behaviour during case A experiments(i.e. the conventional triaxial experiments) the rocks were found to be in a superdense state for a case B stress path and in an ultra-dilatant state for a case C stress path.

    • EPICENTRAL MIGRATION AND PRECURSORY ACUPOINTS

      1985, 7(4):94-103.

      Abstract (429) HTML (0) PDF 534.35 K (507) Comment (0) Favorites

      Abstract:1985年5月,在昆明举行了西南地震工作二十周年纪念大会。作者在会上宣读了震中迁移与前兆穴位的论文。本文就是在这篇论文的基础上写出的。
      我们发现在过去震中迁移的始发点上的前兆手段一旦观测到短临异常,则台址附近有震或历史上震中迁移所至之处有震(误差约60公里)。另外过去地震幕的开幕点上的前兆也具有类似的情况。我们称震中迁移始发点为震迁穴,称开幕点为开幕穴。
      为了理解上述现象,我们可把震中迁移广义化为构造事件的迁移。这种构造事件速度快者为地震,次快者不发射地震波,但可引起其他前兆。据此可把甲地向乙地的构造事件迁移分为以下三种情况。
      1.快速事件(地震)→快速事件(地震)
      2.次快速事件(前兆)→快速事件(地震)
      3.地震(快速事件)→次快速事件(后效)
      如果一个迁移带上已表现过第一种情况,则第二和第三种情况也可能表现。其中第二种情况具有前兆定向预报的意义,是本文讨论的重点。
      对于震迁穴上的前兆为什么属于短临前兆的问题,我们可用立交模式和调制模式相结合来解释。从调制模式的角度来看,地震迁移始发点和开幕点一旦呈现后,若历时又不很长,则它们是容易被调制的地点(简称易调点)。易调点被外因调制后可触发下岩石圈中的蠕滑断层传播,从而引起其他地段的大震发生。
      我们认为前兆穴位可分两种:一种为静态穴位,如由构造条件和台址条件决定的穴位;另一种是动态穴位,如由地震活动图象决定的穴位。本文还提出了构交穴、库渗穴、震后穴、垂烈穴和址良穴等。这些都需要进一步研究。
      以上讨论的是用前兆资料结合历史上震中迁移资料预报地震的方法。这只是预报方案之一。另一方案是前兆观测点附近有震,其发震日期仍按调制公式计算,其震级可按前兆范围半径R与震级M的关系式计算。从组合模式出发,作者和秦保燕得出以下公式:
      R=1/2(100:62-1:35+100:48-1:57)
      若取近似式,则为:
      logR=0.5M-1.4
      式中R以公里为单位。如用单台前兆资料,则不同的R相应不同的震级。

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