1992, 14(1):3-9.
Abstract:A method is presented, which makes it possible to calculate velocity and interface depth of the reflected wave in a vertically inhomogeneous medium. When no information from some depth range of the earth interior is received on the earth surface, the seismic wave velocity in this depth range is considered continuous and can be computed using the travel-time curve of the reflected wave of its bottom interface. Three models are studied and a good result is obtained, in which the reflected interface depth is satisfactory. As phase comparison cannot be done in most artificial seismic data, it is difficult to find the evidence for the existence of low velocity layers. The method presented here provides a solution to this problem.
Feng Deyi , Guo Ruizhi , Gao Yuan
1992, 14(1):10-17.
Abstract:In this paper, the temporal variations of S-wave splitting before some moderately strong earthquakes in North China were studied by using two methods. The first method is a usual analysis of direct S-waves on the seismograms recorded on surface and in boreholes at Jixian, Jinghal. Wuqing stations of Tianjin Network. For increasing the distinguish ability, the statistic method of data analysis was applied too. The second method is an analysis of S-wave polarization by using the digital records of Baijiatuan Station, Beijing. The temporal variation of S-wave splitting before 1989 M=6.1 Datong earthquake was studied. The results show that the premonitory variations in S-wave splitting before some moderately strong earthquakes in North China may be observed and discovered, and it can be considered as an index reflecting the seismic velocity anomalies.
1992, 14(1):18-21.
Abstract:This paper analyses the characteristics of Ms ≥ 5 earthquake activities since 1988 in Chinese Continent and finds the activities are in clustering. It proposes practical indexes predicting coming Ms ≥ 6 earthquakes in Chinese Continent using duration time of lacking Ms ≥ 5 earthquakes and discusses the application of the indexes in earthquake prediction.
Yang Xiuxin , Chen Yuanjun , Yi Zhigang , Lu Yuejun , Zhao Jingmei
1992, 14(1):22-28.
Abstract:Before and after the Datong-Yanggao earthquake in October 1989, a high precision ther-mometer (resolution 0.0001℃) installed at the Sanmafang Ooservatory, which is about 75 km from the epicenter, recorded a significant geothermal anomaly. The amplitude of the anomaly is 0.15℃ and the duration time is over 50 days. This paper discusses the characteristics of the abnormal temperature variation. As a whole, the variation has a shape of increasing temperature with a type of the power function, and is a temperature effect due to the fault creeping caused by the increase of regional stress field. Several days before the earthquake, the geothermal precursory anomaly showed a process that is, "declining-decline rate slowing down-sharply rising-short-term stableness-an earthquake occurring". The mechanism of the geothermal anomaly is also studied, preliminarily.
1992, 14(1):29-36.
Abstract:This paper discusses the relationship between the types of earthquake-generating faults and the earthquake types which occurred on the faults with various types. The authors consider that the type of earthquake occurred on arc-like fault is mostly mainshock-aftershock type or main shock-strong aftershock type; the flat-straight fault leads to mainshock-weak aftershock type; the fold line fault leads to the continuous great earthquake type; the conjugate fault contrast with the double shock type when the conjugate angle is located tensile strain region and the broken faults region have seismic swarm type. It points out the effect of structural condition at focal end, which has modulating action, on earthquake type, whether, the structure at focal end can offer enough abdicating condition for fault disturbance during earthquake or not will result in the difference of earthquake type. Finally, it also discusses the effect of geographic conditions of seismic fault on the maximum seismic intensity, and some questions that need studying in future.
1992, 14(1):37-44.
Abstract:In this paper, the far-field body wave radiation of the fault which contains a asperity is studied by using dislocation model. Assuming that the ratio of the asperity size to the size of whole dislocation surface is C. and the fracture begins in the center, it calculates the effect of different C-values on the far-field seismic wave spectrum. The results show that comparing with the far-field amplitude spectrum of even penny-shaped fault because of the existence of asperity, it, is different that it causes the splitting of beginning part of wave spectrum in the first wave base when the fracture propagates to the fringe of the asperity. It is obvious that the asperity size effects on the amplitude spectrum. In addition, comparing P-wave spectrum with S-wave spectrum, it is found that the corner frequency of P-wave is higher than that of S-wave.
Fu Yinfa , Ge Yanshan , Li Gang
1992, 14(1):45-54.
Abstract:In this paper, based on the 291 P-wave data of 83 local earthquakes recorded from the 12 digital stations of the Telemetered Seismic Network of Lanzhou, the crustal Qp values in and around the eastern area of Gansu Province are obtained, ranging from 170 to 1300. by using the spectrum method in frequency domain. The results show that small and moderately strong earthquakes centered in the low Qp region. but the seismicity was keeping the lowest active level in the high Qp region:the large destructive earthquakes (M ≥ 6) occurred on the boundary between the low Qp and high Qp region. Finally, it analyses the Qp-value distribution by using the combination model, and gives a hazard estimation of potential earthquake in this area.
1992, 14(1):55-61.
Abstract:Comparing the earthquake phenomena with the characteristics of static force breaking and fatigue breaking, the author considers that the fracture and faulting in rock causing earthquake are fatigue breaking. Based on some results about studying fatigue fracture law of compressed vessel and chemical machines at the end of 1970s, the author has calculated conscientiously, regarding the earth as a spherical vessel with thin wall. The results show that fatigue breaking in 35°N zone of the earth is the most severe, regardless of the action of centrifugal force of the earth rotation or the gravitation of any celestial body in the solar system. Thus, the cause of intense seismicity in 35°N zone is revealed.
1992, 14(1):62-71.
Abstract:Based on a point of view that the near-field seismic source can't be considered as a point source, the author derived a formula for focal depth corresponding to the line and plane sources from their radiant field as follows:h=r1√10(10-1i)/(1.5m)-1
Where I0 is the seismic intensity at epicentre, I1, the intensity at observation point i, and r1 the radius of the isoseismal curves defined by the intensity I1, the index n of geometrical diffusivity within macroseismic field is a varible parameter. For n=2, it is G-R-Min formula, for n=1-2 corresponds to S=1.5-3.0 in Blake formula, n=1.78, Blake formula et al. And importantly, first gave the value of macroseismic focal depth to a standard error in the world.
1992, 14(1):72-77.
Abstract:Based on the constructing practice of the China-Seismology-Journal-Paper (CSJP) documental database (English edition) for several years, this paper deals with the significance and complexity of the quality control in the construction of the CSJP documental database (English edition) under the decentralized condition. It presents the construction mode of the documental database, and the quality control mode, control objective and control measures in the process of decentralized indexing for documental data. It is pointed out emphatically that in order to guarantee the quality of the CSJP decumental database (English edition), the indexing staffs must adopt firmly the idea of quality first, and it is necessary to establish a control centre with high-degree authoritativeness and high efficiency administration.
1992, 14(1):78-78.
Abstract:1991年在海南岛海口举行的全国地震学专业委员会会议上,我们曾提出了统计物理学中的"临界乳光"和λ型在地震预报中的重要意义。现以短文作简要论述。
1992, 14(1):79-81,77.
Abstract:近年来,地震窗预报方法已在国内广为应用。富蕴地震窗系笔者在王泽皋、姜秀娥等人工作的基础上[1-3],于1984年在全国地震预报清理攻关中建立,在1987-1988年全国地震预报实用化攻关中又得以进一步深化和完善[4]。
1992, 14(1):82-85.
Abstract:1990年4月26日在青海省共和县发生了Ms7级地震。甘肃省地震局对这次地震的余震趋势做了正确的估计,并对5月7日和16日两次5.5级地震做了较为准确的预报。在预报过程中,使用的还是一些传统的测震学方法,但在资料选取和如何划分余震活动时间段方面,做了一些技术性改进。
Zhang Chaoming , Li Minli , Shu Keming , Liang Jiuliang
1992, 14(1):86-88.
Abstract:目前,水氡及水中溶解气及其组分的观测,作为一种地震前兆的监测方法已在水化台站全面推广、应用,并取得了一定效果。但是目前的观测均以氡气和其他气体在水中的溶解部分为主,这显然是有一定局限性的。
1992, 14(1):89-91.
Abstract:自然电位Vsp作为地电台站的正式观测项目,一直与地电阻率同时观测。尽管各地电台都积累了大量的自然电位资料,但对这些资料作认真地分析研究却很少。
Tao Shufen , Wang Changling , Liu Yaowei , Jiang Dayong , Shen Kejin , Ning Zhizhen , Chen Lanqing , Lei Lansheng
1992, 14(1):92-95,85.
Abstract:近年来,国内外不少学者致力于气体地球化学元素预报地震的研究,但对断层气的干扰因素研究较少。作者对此做了初步研究。本文介绍了主要研究结果。
Liao Yuanmo , Wang Duojie , He Genqiao , Chang Qiuju , He Zhenrong , Zhao Chengwen , Zhou Huaguo
1992, 14(1):96-97.
Abstract:龙首山北缘断裂带是甘肃西部重要的强震活动带。地震活动资料表明,该断裂带上的中强地震主要集中分布于西段的保得河断裂上,如1954年山丹7(1)/(4)级地震等;而东段的白家咀断裂尚无历史地震的记载。
Chen Jiachao , Qin Baoyan , Feng Xiaying
1992, 14(1):98-111.
Abstract:Delineation of the focal area of historical major earthquake is important because only when the location and dimensions of the focal area and the strike of the earthquake-triggering structure are definitely known will we be able to carry out calculation on the influence field of major earthquake.
Sopyright:China Earthquake Engineering Journal