• Volume 11,Issue 4,1989 Table of Contents
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    • RENORMALIZATION GROUP METHOD APPLIED TO EARTHQUAKE PREDICTION

      1989, 11(4):1-13.

      Abstract (482) HTML (0) PDF 962.72 K (806) Comment (0) Favorites

      Abstract:From the point of view statistic physics and the renormalization group method, we studied the rupturing of a 1-D and a 2-D focal body, after the stress accumulation of the stress accumulation element in the combination model was into the nonlinear period. The critical value of the rupturing probability of the focal bodies is 0.2063, 0.1707 respectively. Using the rupturing critical value of the 2-D focal body, we got the critical ratio of the gap energy to the reference energy is 0.1872 for a seismic gap. The value 0.1872 was examined using ten seismic gaps from 1967 to 1980 and the seismic gaps (starting magnitude: ML=2, 3) from 1982 to 1986 in the eastern part of China. The results are satisfactory.

    • PREMONITORY FLUCTUATION AGGRAVATION AND IMPENDING EARTHQUAKE PREDICTION

      1989, 11(4):14-24.

      Abstract (538) HTML (0) PDF 883.31 K (831) Comment (0) Favorites

      Abstract:Fluctuation aggravation is a kind of critical phenomenon before suddenly phase cnange. In this paper we discuss premonitory fluctuation aggravation before strong earthquake at this point, such as small earthquake frequency, underground fluid, gas and earth stress and so on. The preliminary conclusions are as followss:
      1. Before strong earthquake, the space distribution of small earthquakes which exceed average day active level in a large area is of the orderliness-the active belts of small earthquakes pass through the coming strong earthquake area. The intersecting area of two belts is the site of coming strong earthquake.
      2. Before strong earthquake, most of the high frequency day of small earthquakes synchronize the time of the external causes, the external causes that are found at present include syzygy, solar term, magnetic storm exceeding middle level, and atmosphere pressure fall and so on. This kind of high frequency activity of small earthquakes usually appears a month or a day before the coming strong earthquakes.
      3. The time of the premonitory fluctuation and the time of small earthquake frequency fluctuation are approximately synchronization, there are relations between them in the cause of formation.
      Impending prediction indexes of earthquake as stated here are not only applicable to the many foreshork area, but also to few foreshork area. Because there are many times of premonitory fluctuation before strong earthquake, it is not possible to completely eliminate false for the time prediction of the strong earthquake.

    • A STUDY ON ATTENUATION LAW OF SEISMIC GROUND MOTION IN THE LOESS REGION OF THE NORTHWEST CHINA

      1989, 11(4):25-36.

      Abstract (504) HTML (0) PDF 749.26 K (737) Comment (0) Favorites

      Abstract:In this paper, according to the geological structure, geomorphic feacture and the characteristics of seismic activity, the author: divided the loess region of the Northwest China into four subregions and studied their attenuation laws of seismic ground motion. The results show that the attenuation rate of intensity as well as seismic ground motion becomes slower from the western region to the eastern region with the increasing of the thickness of soil stratum. Before statistical analysis, the authors made linear interpolation of isoseismic contours to consider the uncertainty of attenuation. The authors also put forward a new thought, that is, using the Q value to adjust the parameters of attenuation law of seismic ground motion.

    • PRELIMINARY DISCUSSION ON THE PRECURSORY CHARACTERS AND MECHANISM OF THE SEISMIC DEEP ELECTRICAL CHANGE

      1989, 11(4):37-45.

      Abstract (500) HTML (0) PDF 862.10 K (449) Comment (0) Favorites

      Abstract:In this paper, the conductive mechanism in situ of the high-resistive layer which is 10-25 km in the crust is discussed. It is indicated that the conductivity of the rock block in the layer mainly depends On the crack-porosity behaviour and distribution of porous water in it. Using the theory and numerical modeling of conductivity of partial melt, we can see that when the connection weight factor increases, the volume conductivity in situ of the layer sharply decreases. Analysing the characters of the strain with porous water in and around the focal region, we illustrate the precursory regionalization of the deep electrical change which probably appears during earthquake readiness, explain the characters of the regional volume resistivity and conductivity anistropy change, preliminarily diccuss the physical mechanism of the electrical change, and roughly estimate the possible values.

    • THE STUDY ON THE SITUATION AND STRONGER EARTHQUAKE ACTIVITY FEATURES IN THE NORTH AREA OF THE QINGHAI-TIBET PLATEAU

      1989, 11(4):46-54.

      Abstract (483) HTML (0) PDF 698.80 K (671) Comment (0) Favorites

      Abstract:The features of seismicity in the north area of Qinghai-Tibet Plateau are obtained:
      (1) The active period of earthquake is about 230-250 years long, the tranquil period is about 130 to 150 years long.
      (2) The seismicity has a relation to the seismic activity in the south area and the south edge of the Himalayas. After stronger earthquakes occurred in the south area of the Himalayas and the north area of Burma, there would be stronger earthquakes to occur in these areas with probability 87.5% and 66.7%, respectively.
      (3) The earthquakes with M≥7 took place alternatively in several seismic zones. The first two earthquakes with M=6 would point out the furture location of next earthquake with M≥7.
      (4) The medium earthquakes were not in active before the earthquakes whth M≥8, but were active before the earthquakes with M≥7. Generally, the medium earthquakes happen in north and west parts of Qinghai and southeast part of Gansu or in the edge of Gansu and Sichuan before the earthquakes with magnitude about 7.
      According to above results, there may be an earthquake with M≥7 in the north area of Qinghai-Tibet Plateau in coming 10 years.

    • STUDY OF RUPTURE PROCESS AND INSTABILITY MODE OF STEP-LIKE ASPERITY ON SLIDING PLANE IN ROCK

      1989, 11(4):55-63.

      Abstract (582) HTML (0) PDF 2.00 M (809) Comment (0) Favorites

      Abstract:The rupture process and instability mode of step-like asperity located on sliding plane in granite specimen were studied under triaxial compression at confining pressures of 300-500 MPa. The main experimental results are as follows:
      when differential stress (σ13) reaches 0.15-0.17 (σ13)c, where(σ13)c is the peak stress level of the first event of stickslip, macroscopic fracture takes place along the base of step-like asperity and the linear relation between stress and displacement is kept; with increasing stress level fracture propagates and cuts through the original asperity at (σ13)≥0.3(σ13)c, and in the meanwhile, some new lower asperities are formed; as (σ13)≈(σ13)c, the sliding plane originally with asperity has been flattened relatively, and after that, the sudden instability with large stress drop and violent shock occurs.
      The results indicate that the failure of asperity can only cause micro-or fore-shocks and acoustic emission, and the main shock of earthquake is induced by stick-slip along a flattened fault zone. In other words, the mechanism of strong earthquake is not the fracturing of asperities, but the unstable sliding along relatively flatten fault zone.

    • APPLICATION OF FUZZY-RELATION EQUATION IN PREDICTING MAXIMUM MAGNITUDE RANGE IN NORTH CHINA

      1989, 11(4):64-70.

      Abstract (501) HTML (0) PDF 474.05 K (682) Comment (0) Favorites

      Abstract:In this paper, 16 items of 4 factors used in distinguishing magnitude interval related to maximum event that might happen every year are chosen, and the earthquake sequences of Ms≥4.0 (in exception of aftershock) occurred in North China from 1960 to 1986 are dealt with. Fuzzy relation equation of magnitude decision containing 3 magnitude intervals, Ms≤6.0, 6.0s<7.0 and Ms≥7.0 are given. Seven event examples are used to inspect the prediction result of this equation. The result indicates that all of them passed through prediction inspection. This paper also made a estimate that maximum event of which magnitude would be Ms≤6.0 might occur in North China in 1987.

    • THE SHORT-TERM AND IMMEDIATE ANOMALOUS PATTERNRECURRENCES OF THE APPARENT RESISTIVITY BEFORE THE TANGSHAN AND SONGPAN EARTHQUAKES OF 1976

      1989, 11(4):71-75.

      Abstract (512) HTML (0) PDF 402.21 K (863) Comment (0) Favorites

      Abstract:This paper introduces the observations at Changii, Hebei Province and Wudu, Gansu Province geoelectric stations (△≤100km) for two major earthquakes (Tangshan earthquake on July 28, 1976 and Songpan earthquake on August 16, 1976). The results of short-term and imme diate precursors were carefully checked and compared with each other. We got a similar precursory phenomenon which was not contingency. The similarity suggests that the similar anomalous phenomenon is objective; the electrical method (apparent resistivlty) is a hopeful methodfor earthquake prediction.

    • A INTERPRETATION ON THE SEISMICITY AND MECHANISM OF EARTHQUAKE OCCURRED IN HECHI REGION, GUANGXI USING THE RESULTS OF ROCK EXPERIMENT

      1989, 11(4):76-82.

      Abstract (527) HTML (0) PDF 571.62 K (685) Comment (0) Favorites

      Abstract:In this paper, we have discussed the temporal-spatial distribution of seismicity, "window effect" of stress field and the feature for small in magnitude but high in intensity in Hechi region, Guangxi. A qualitative interpretation for the mechanism of earthquakes occurred in this region has been done using some results of rock experiment.
      The region is situated in two intersecting faults and it is sensitive to stress. The research result shows that the seismicity attributed to stick slip of existing fracture under low stress in very inhomogeneous medium. Special geological setting can not compose a condition preparating great earthquakes and the seismicity can not constitute a threat to Longtan reservior region nearby.

    • STUDY ON THE CRUSTAL ACTIVITY IN THE SOUTHERN SICHUAN AND THE PARTIAL AREAS OF YUNNAN AND GUIZHOU PROVINCES

      1989, 11(4):83-90.

      Abstract (497) HTML (0) PDF 621.74 K (702) Comment (0) Favorites

      Abstract:Based on the splaying features of surface structure, the background of gravity field and magnetic field, and the basement structure features from aeromagnetic survey, the crustal structure, tectonic stress field and potential focal region in the southern Sichuan Basin and the adjacent areas of Yunnan and Guizhou provinces are discussed. The results show that the tectonic stress field of these areas is of multidirectivity and multiperiodicity. In Palaeozoic era the direction of principal compression stress was about SN, and now about EW. The deep fault activity in EW is not obvious, only has a few of microearthquakes. But the areas Which EW deep faults intersect other direc tional faults often occur earthquakes. And the areas which the basements, of different rock feature border on are also the seismic prone areas.

    • >短文
    • THE CHARACTERISTICS OF GEOELECTRIC ANOMALIES OF DEEP BURIED ELECTRODE BEFORE THE HEZE EARTHQUAKE WITH MAGNITUDE OF 5.9 IN 1983

      1989, 11(4):91-94.

      Abstract (470) HTML (0) PDF 285.24 K (629) Comment (0) Favorites

      Abstract:笔者通过对大量地电资料的分析,发现深埋电极进行地电观测,能够排除表层干扰,突出地震异常。本文利用深埋电极的地电观测资料,总结了1983年菏泽5.9级地震前地电异常特征。

    • DEFORMATION OF THE ELASTIC EARTH TIDES CAUSED BY OCEAN LOADING

      1989, 11(4):95-100.

      Abstract (487) HTML (0) PDF 408.81 K (471) Comment (0) Favorites

      Abstract:根据自由振荡理论,质量负荷作用下的地球形变平衡方程[1]形式为。

    • PRELIMINARY ANALYSES ON THE PERMEATION ENVIRONMENT AND INDUCED EARTHQUAKE EFFECT OF DANJIANGKOU RESERVOIR

      1989, 11(4):101-104.

      Abstract (516) HTML (0) PDF 374.20 K (448) Comment (0) Favorites

      Abstract:丹江口水库自1967年11月开始蓄水。1970年1月起,库区一些特殊地段开始出现了明显的地震活动,并分别于1972年4月3日和1973年11月29日发生了林茂山3.5级(Ms)地震和宋湾4.7级(Ms)震群活动。

    • MIGRATION AND DIFFUSION OF SEISMIC ACTIVITY OBSERVED IN THE JAPANESE ISLANDS

      1989, 11(4):105-116.

      Abstract (538) HTML (0) PDF 802.09 K (610) Comment (0) Favorites

      Abstract:Migrations of seismic activity observed after large earthquakes which occurred in and near the Japanese Islands are investigated, A common feature of migrational phenomena in the six cases which are studied in this paper is that migration occurred along geological tectonic zones, Sometimes existence of active tectonic zone is reconfirmed by the appearance of migrational phenomena, Analogizing to plate boundary regions where seismic activity is known to migrate or diffuse along mechanically coupled plane, we can consider that inland active tectonic zones correspond to mechanically interacting boundaries of crustal blocks. It is likely that more than one type exist in miqrational phenomena. In the cases we investigated following characteristics are observed that velocity of migration is about several km/year, seismic gaps remain between focal regions of large earthquakes, and there are seismically active periods in each seismic belt. A possible mechanism of migration is successive break down of asperities in which tectonic stress concentrates by relative movement of crustal blocks.

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