Qin Baoyan , Yao Lanyu , Wang Jin , Li Yarong
1990, 12(2):1-15.
Abstract:Using the initial phase, breakout phase and stopping phase of long period P-wave records of WWSSN, we have studied the source rupture process of the 1976 Songpan great earthquakes (Aug. 16, M=7.2; Aug. 22,M=6.7; Aug. 23, M=7.2), and got the dynamic parameters of sources of the three great earthquakes. The length of initial rupture area for the three great earthquakes is 8.5 and 6km respectively, calculated by the weaker initial, phase of P-wave. All of the three great earthquakes is two-side rupture, the rupture length of source body is 73, 34 and 54 km respectively.
The result shows that in the source regions, the three great earthquakes exist a part of superposition phenomena, so total source dimension is only 90 km; and the source depth is 9km determined by the breakout phase of the Songpan great earthquake of Aug. 16. It is also found that the obvious stopping phase and quicker rupture speed of source fault are related to the adjustment element located at the ends of source region.
Zhang Cheng , Du Zhijun , Fu Yinfa
1990, 12(2):16-21.
Abstract:This paper determines and analyses crust medium quality factor, Q value, in the eastern Gansu area and Xiji-Haiyuan-Guyuan area of Ningxia, assuming that crust medium is visco-elastie. The mean Q value calculated by power spectrum of the direct P and S wave is 126. The mean Q value is 58 in low value area. The Q values are high in Haiyuan and Lixian area, the mean Q value is 194 and 957 respectively. The Q value is low in Diebu area, its mean Q value is 48. These high and low Q values occurred before and after main earthquake.
Shi Yaliu , Zhang Bi'ao , Wang Xianbin
1990, 12(2):22-26.
Abstract:This paper analyses the fault gases of each segment of large faults in the northern fringe of Qinling Mountain, determines the segment order of strong earthquake risk: the earthquake risk is stronger in the Guide-Xunhua segment than that in the Lintong-Xianyang segment; the earthquake risk in the Qingshui segment is between above-mentioned two segments; and the earthquake risk is stronger in the Tianshui-Hezheng segment than that in the Meixian-Lantian segment. The authors further determine that the Guide-Xunhua segment and Qingshui area are strong earthquake risk areas, and in the Meixian-Lantian segment there will not occur any earthquake (M≥7).
1990, 12(2):27-34.
Abstract:In this paper, a proper fuzzy method has proposed for earthquake prediction. The method includes:(1)Carry on fuzzy statistics of varied phases in two fields of characteristic factor and prediction target; (2)Make multiplication for membership obtained and set up fuzzy relation matrix using condition probability formula; (3)Predict using fuzzy transition and maximum subordinate preference criterion. The test of earthquake prediction in Yunnan region indicates that the method is feasible.
Lu Yangquan , Qian Jiadong , Liu Jianyi
1990, 12(2):35-41.
Abstract:This paper deals mainly with the precursory features of apparent resistivity and acoustic emission of the large scale granite specimen during the process of slowly rupturing due to a dilatancy source. The results show that not only the long tendency of anomaly and shortterm anomaly in resistivity were observed before the main rupture occurrence, but the precursors associated with rupture were observed clearly as well, i.e. a sudden change in apparent resistivity several hours prior to the main rupture occurrence. The precursor in acoustic emission was also recorded in the experiment, the starting time, however, is later than that in apparent resistivity. And there are respective distinctions in the acoustic emission during the initial microrupture and the final main rupture.
Diao Shouzhong , Jiang Haikun , Ren Qingwei , Li Mengluan
1990, 12(2):42-48.
Abstract:In this paper, the time fractals (D) for four moderately strong earthquake sequences are analysed using box counting algorithm. The four sequences have taken place in Lingwu-Wuzhong area of Ningxia since 1971 and have been recorded accurately. The results show that the time fractals are low (D<0.5) in this area. For the double main shock sequence or foreshock sequence, the fractal obtained before the second main shock occurrence is lower than that obtained from aftershock sequence. We have also analysed the frequency attenuation features of four earthquake sequences. It shows that the attenuation coefficient P and b value have synchronous variation. Therefore, we think that the earthquake sequence time fractal may be helpful for judging earthquake tendency in a short period.
Li Qinghe , Min Xiangyi , Guo Jiankang , Wei Deqing , Hou Xiaoyu
1990, 12(2):49-58.
Abstract:The line has twice laid out to sound the crustal velocity structure in Huixian-Lixian region by means of industrial blasts of Changba Lead-Zinc Mine in 1984 and 1985, especially, the explosion of 500 ton charge on Dec. 30, 1985 supports us to interprete a large scope crustal velocity structure. The parts of DSS data obtained by DSS Cooperation Group, SSB, in 1986 were supplemented.
The velocity structure in Tianshui-Lixian region are following:
1.The average thickness of sedimentary layer is about 2.5km, average velocity is 4km/s (P-wave).
2.The average thickness of crust is 43.6km, average velocity is 6.2km/s.
3.There are five layers from surface to Moho. There is a low-velocity layer in depth 24-29 km. The shape of base is rising and falling.A fault in Lixian was found.
4.The joint inversion of P-wave and S-wave was put forward, and P-wave velocity structure and S-wave velocity structure were obtained, The average velocity ratio of crust is 1,732,
1990, 12(2):59-64.
Abstract:In this paper, using Chinese aseismic code (TJLL-78) and statistical information about earthquake damage of multi-story brick building, according to the structure mechanics method, we get formula about assessment PGA. Having investigated, the damage of multi-story brick building of Jan. 4, 1988 Lingwu earthquake, Ningxia, we give PGA and intensity of this earthquake by calculating the coefficient of wall aseismic strength.
1990, 12(2):65-69.
Abstract:In this paper, according to the structure and physical field of the earth, and considering the nature of the hydrogen deduced by its position in periodic table of elements and its electronic distributions and combining the developments of modern codensed states and structural chemistry with ultra-high pressure technique, it is shown that under physical chemistry environments of lower mantle-core, hydrogen encounters about 10~8atm. ultra-high pressure and possesses sufficient potential difference of thermodynamics. Therefore, the hydrogen may be condensed to be metal hydrogen which can principally be regarded as self-excited generator. It reveals the origins of magnetic, gravitational and electric fields of the earth.
Xiang Guangzhong , Wang Duojie , Xu Xiaowei , Jia Yunhong
1990, 12(2):70-77.
Abstract:This paper studies tectonic position, occurrence, depth and active characteristics in Quaternary Period of main active faults in Chaidamu Basin and its vicinity, based on field investigation data, gravity and aeromagnetic data, discusses relationship between the faults and earthquakes. In this area, earthquake activity intensity relates to fault depth; active faults of EW with left lateral movement characteristic of Holocene is closely relative to strong earthquake activity.
Li Tongqi , Yang Chongyi , Yang Jingxiu , Lei Lansheng , Chen Lanqing
1990, 12(2):78-82.
Abstract:滇西实验场位于北纬24°.5-28°,东经98°.5-101°.5,其面积约80000km2。
1990, 12(2):83-85.
Abstract:实践表明,单靠一项手段来预测地震往往是行不通的,比较可取的办法是把多项预报手段的预报意见加以综合分析。在地震的综合预报中,如何确定各手段的权重是一个关键的问题。以往所用的方法带有一定的局限性。本文试图根据模糊数学中的“贴近度”,概念,提出一种比较客观的算法,利用这个算法可以近似地求得各手段的权重分配。
1990, 12(2):86-92.
Abstract:地球基本磁场随时、空有一个周期性的、长期缓慢的变化。
1990, 12(2):93-97.
Abstract:华山北麓断裂是渭河盆地内一条典型的活断层。著名的1556年华县八级大地震就发生在该断裂带上[1、2]。
1990, 12(2):98-100.
Abstract:甘肃东南部地区地震活动频繁。
1990, 12(2):101-104.
Abstract:随着计算机技术的推广普及,单片计算机以其独特的技术优势迅速地渗透到各个技术领域。国外许多地震仪器早已用上了单片计算机,国内在这方面也已取得了可喜的进展。
Geng Dayu , Han Chengjian , Bai Baoyu , Yan Qingmin , Li Zhongsheng
1990, 12(2):105-112.
Abstract:The active pictures of XGF (Xi'an Ground Fissures) are given and analysed. Both tectonic characteristics and artificial characteristics of XGF are shown. The tectonic control functions on XGF appear not only geometrical but also mechanical, the former can be seen from space distribution feature and geometrical pattern of XGF, the latter can be seen from its formation process, as well as the time feature of earthquakes and XGF. The human activities, mainly overextraction of piezometrie ground water, result in land subsidence in Xi'an. The ununiform land subsidence is responsible for high rate of the movement of XGF, which is about ten times higher than the rate of tectonic movement. According to the major rate(the rate of vertical slip), XGF is classified into three grades. The map of XGF classification well reflects its multiplicate cause mechanism.
Sopyright:China Earthquake Engineering Journal