1990, 12(3).
Abstract:
1990, 12(3):1-13.
Abstract:The Gutenberg-Richter earthquake frequency-magnitude relation is one of the most universal laws in the seismicity. Explaining B. Gutenberg formula in physics, two theories have been acccepted extensively. One is the theory caused by medium heterogeneity which was proposed by K. Mogi, the other is the theory caused by stress level which was proposed by C. H. Scholz. They individually built B. Gutenberg formula from probability calculating formula along with individual reasoning. However, actual Gutenberg-Richter formula shall be relation which reflects both medium character and stress level. So two forms which were built individually by K. Mogi and C. H. Scholz are very alike in appearance, but they are essentially unilateral. This is the reason why it is necessary to study physical mechanism of b value in this paper. Starting from real geo-medium and using fracture theory, Gutenberg-Richter formula is calculated. Our result of b value expression accords with result obtained from rock breaking experiment. So K. Mogi and C. H. Scholz theory is unified in theory.
1990, 12(3):14-18.
Abstract:Based on practical data obtained in microzonation of Baoji City and Xi'an City, a random 1-D model for soil layer is set up in this paper. Using the theory of random vibration and the method of perturbation, the effect of random site condition on the earthquake response analysis of soil layer has been studied preliminarily. The results show that the randomness of soil mechanical parameters usually can make the variance of earthquake response on the surface of soil layer has a change of 20% around its mean value, and it also can make the free frequency of soil layer has a change between 15%~40%. So that, it should be paid more attention to the randomness of soil mechanical parameters on the earthquake response analysis of soil layer.
He Zhengqin , Zeng Rongsheng , Chen Guoying
1990, 12(3):19-22.
Abstract:In this paper, the crust structure of North-South Seismic Zone and its western side has been studied using long-period surface wave data. The results show that the crust in north and west parts is thicker than its south and east parts. Low-velocity zone exists within the crust of the whole area of North-South Seismic Zone and its western side. The average S-wave velocity is very low, about 3.37 km/s, and the velocity in the uppermost mantle is 4.40 km/s. It is possible that there is an uprising of mantle materials in the north section of North-South Seismic Zone and the thickness of lithosphere is only 60 km with a low-velocity zone in the bottom of the crust
Shi Telin , Guo Daqing , Yang Yuheng , Guo Jiankang , Xiao Lizhu , Sun Jingfang
1990, 12(3):23-32.
Abstract:Fractal geometry is applied to the quantitative analysis of Qilian Mountain fault and Longshou Mountain fault. Using the circle area covering method, the fractal dimensions for every segment of Longshou Mountain. fault range from 1.308 to 1.434 with confidence 99%. Using ruler method, the D values of the total fault, west segment, median segment and east segment for the main fault trace of Qilian Mountain are respectively 1.0118, 1.0043, 1.0154 and 1.0075 with confidences 95-99%. And by means of circle area covering method, the D values are 1.518, 1.549, 1.537 and 1.460 respectively for the total fault and every segment of Qilian Mountain.
The study results show that the fractal dimension D may express fault hetereogeneity, irregularity, complexity and so on. But according to the results, the correspondence between earthquake activity and fractal dimension is not Obtained. There is a slight correlation between the fractal dimension and the branch number and the occupied area of branches.
1990, 12(3):33-37.
Abstract:This paper gives an outline of historied observations of gravita-tional earth tide in Lanzhou, and the tidal gravity parameters measured by different instruments. Comparative analyses about observation data, monthly harmonic analysis, and repeated accuracy of major-wave tidal factor between GEO-765 and modified GS11-150 gravimeter are made. The seismic monitoring capacity by using modified GS11-150 gravimeter in Lanzhou is evaluated. Finally, the part of results measured by old GS11-150 in Tianshui, Gansu Province is also introduced.
Guo Jingxin , Hou Zhenqing , Hou Kangming
1990, 12(3):38-43.
Abstract:Changma-Qilian fault is a major active fault zone in north-eastern margin of Qinghai-Tibet Plateau. Its median section (Xiangtaizi-Sidalong in Sunan County,Gansu Province)has had obvious activity in Holocene, and has been appearance of offsetting Holocene stratum along with offsetting ridge and stream system, the fault scarp and palaeoseismic collapses, landslides and so on.
According to distribution and character of palaeoseismic collapses and landslides, C14 dating of correlative accumulation 9 we estimate that at least one palaeoearthquake(M=7.0-7.5)occurred about 4680yr. B. P. Finally, the earthquake risk of this section is discussed.
1990, 12(3):44-49.
Abstract:Using 40 mechanism solutions of earthquake focus and 3 synthetic solutions of small earthquake, the crustal stress field in and around Gansu region is discussed. The directions of P-axes from the western area to the southeastern area changed from N40°E to N90°E step by step. The horizontal directions of P-axes are vertical to the northeast edge of Tibet Plateau, and the elevation angles of P-axes are less than 30°. It will be shown that the power source of this region is caused by the collision between India and Eurasia plate. The change of regional stress field is of great value for discussing the fault activity.
1990, 12(3):50-53.
Abstract:Using the attenuation coefficients of amplitude and predominant frequency, the small-event Q value before moderate-strong events has been calculated. Summing up the typical earthquakes occurred in different regions, it can be seen that the small-event Q value continuous increases before the moderate-strong events take place, the amplitude of Q value increase is several times larger than that of the normal value. Never-theless, the amplitude of the anomalies is irrelevant to the magnitude of the subsequent earthquake, yet the duration of the anomalies is related to the magnitude of the subsequent event. Larger earthquakes trend to be preceded by longer duration of anomalies.
1990, 12(3):54-56.
Abstract:This paper has analysed the data from four earth-resistivity observing stations in Yunnan Province since 1980, and finds that there is a obvious anomaly of earth-resistivity from Tengchong station before the Lancang earthquake (M=7.6) . It has two features: first, the non-isotropic phenomenon of earth-resistivity is clear; second, the earth-resistivity prior to the earthquake has distinct Stages.
Chen Youfa , Kang Yunsheng , Du Xuebin , Chen Baozhi , Hou Kangming , Liang Geshu , Dong Yongde , Zhang Hequan , Liang Gezhe , Jiang Zhongxian
1990, 12(3):57-63.
Abstract:In 1985-1988 at Minle earthquake risk region, Gansu Province, the regular measuring has been carried out by using the method of dipole electrical sounding with current electrode spacing AB=1km, receiver electrode spacing MN=0.95-1 km, central distance of dipole R=5-8 km. The results show: (1)Apparent resistivity ps does not have yearly variation; (2)The ps variation, about 10 days before the M>4.0 earthquakes, is 3-8% in range of 100 km to the observation point.
Liu Guangxia , Zhao Wenjun , Ren Wenju , Wu Xiuyun
1990, 12(3):64-71.
Abstract:This paper mainly describes the preliminary results of deep crustal structure in north-eastern Shanxi Province and its vicinity from 3-D gravitational forward and backward calculation with the help of geological and regional gravity data. By 3-D normal calculation, the residual gravity at various depths is obtained, then, the plane distribution of crustal thickness in the whole region is inversed using the given depth of Moho. Based on the results above, the ‘top-deep’ varia-tion of some active faults and structures is simply discussed. In addition, the deep crustal tectonic background of the earthquakes and the Quaternary volcanic activities is studied. It is also found that there maybe exists a shear tectonic belt at depth along 40°N.
Duan Ruwen , Zhang Zhenzhong , Li Lan , Wang Jun
1990, 12(3):72-78.
Abstract:By means of experiments and systematic analysis of the data, the further research on dynamic characteristics of loess was made. The results show that the typical loess (i.e. of Q3 and Q4)have special earthquake engineering property-the seismic subsidence (i.e. subsidence caused by earthquake). Loess is sensitive to earthquake and its subsi-dence is relatively more serious at the beginning of earthquake; strength of wet loess decreases with earthquakes and sometimes it can even be liquefied.
Chang Qiujun , He Genqiao , Guo Yuying
1990, 12(3):79-85.
Abstract:This paper introduces the measuring method of gas mercury content in soil, the selection of optimal observing conditions of JM-3 gold membrane measuring instrument and the observing results of gas mercury content in soil in A'erjin Fault and its vicinity. Before the Menyuan earthquake(M=6.4, 1988)and the Lancang earthquake of 1988 etc., the sudden changes of gas mercury concentration were observed. The Xiwudang earthquake, Zhangye, Gansu Province on Sept. 12, 1987 was predicted using the change of gas mercury concentration in soil.
1990, 12(3):86-86.
Abstract:安徽省霍山地区自1970年以来多次发生震群活动。这些震群主要分布在北纬31°20'-31°31',东经116°00'-116°15'范围内,而其中80%的小震又都集中在诸佛庵、黑石渡、落儿岭、桃源河所围限的区域内。
1990, 12(3):87-87.
Abstract:我们研究了我国Ms≥5.0级地震的时空分布和强度特性,发现台湾地震活动似乎是我国大陆强震的前兆震(或震群)。
1990, 12(3):88-90.
Abstract:河北地震带位于太行山东麓,从磁县起经邢台、河间、北京及唐山附近,止于燕山南麓。总体走向为北东向,长约900km,宽约150km。
1990, 12(3):91-91.
Abstract:近年来,文昌县蓬莱区南和村水井两次出现翻滚、冒泡现象。第一次发生在1983年10月5日上午8时,井水有两处翻滚、冒泡,持续5天,9日结束。第二次发生在1986年5月22日下午2时,井水有7处翻滚、冒泡,至26日结束,持续时间为5天。
1990, 12(3):92-95.
Abstract:美国地震学者[1]>P.G.Okubo等人(1987)在帕克菲尔德-索尔顿湖长达近千公里的圣安德烈斯断裂带上,分六段对该断裂进行了分维解析,发现该断层具明显的分维结构,计算出六段的分维数为:1.12~1.43。研究结果表明,较大的分维数D值与断裂带上断层几何形态复杂的地段相对应,同时这些地段又是历史强震区。
Sopyright:China Earthquake Engineering Journal