Ma Qinzhong , Zhao Heyun , Qian Jiadong
1993, 15(2):1-5.
Abstract:This paper deals with the numerical simulation of the changes of apparent resistivity caused by topographic undulation based on the model of 2 D layered medium by using the boundary element method, and the general calculating method of apparent resistivity under the condition of abnormal surface topography in the horizontal layered medium and the influence of topography on geoelectric precursor are also discussed. The results show that the bigger the changes in topography, the less the information in apparent resistivity changes from deep depth. Thus, the proportion of precursory information could be reduced. From this point of view, big undulation in topography could be unfavorable for geoelectric resistivity monitoring.
Song Huizhen , Liu Jie , Lan Yingang
1993, 15(2):6-12,23.
Abstract:This paper deals with a equivalent theory between the constructive plane dispersed by the technique of splitting node and the uneven dislocation plane, which lie in the elastic and viscoelastic medium, and judging from this the displacement field expressed with FEM dislocation formula are equivalent to that with Volterra dislocation formula. Thereby, the unified theory and method calculating the displacement field and the stress field induced by the fault plane slip are obtained. Namely, the displacement or the displacement rate on the fault plane are inversed based on Volterra dislocation formula and geodetic date, and then the displacement field and the stress field are calculated by means of FEM dislocation formula and the inversed value of the fault dislocation.
1993, 15(2):13-23.
Abstract:In this paper, we have studied the features of fault gouges, the fault activity and the mode of fault slip in the eastern segment of Altun Fault Zone by means of the scanning electron microscope and X ray etc.. The results are as follow: 1) The activity has been decreasing from east to West in eastern segment of Altun Fault Zone since Late Pleistocene Epoch. 2) There were at least. 2-3 palaeoearthquakes during Quaternary Period. 3)The fault has been mainly in stick slip from Subei to Arkesai, and in creep slip from Bage Valley to Changma Dam since Holocene Epoch.
Min Xiangyi , Hou Xiaoyu , Zhang Youmin , Yu Xuejun
1993, 15(2):24-29.
Abstract:The seismicity of 5°×5° around Jingtai region in Gansu from Jan. 1979 to Sep. 1990 is analysed by means of time space scanning. The blocking segment of seismotectonics of the Jingtai Ms6.2 earthquake on Oct. 20, 1990 is determined. This blocking segment is located in the middle of Menyuan-Haiyuan tectonic belt. The scanning result shows that the earthquakes of Ms≥2.0 occurred mostly on Menyuan-Gulang segment and there are a few on Xiji-Haiyuan segment in that period. The seismicity of these segments echoes each other, and on Xiji-Haiyuan segment the seismicity is delayed for three years. It is possible, that the blocking segment and start time of blocking be found if analysing seismicity by means of time space scanning, and being combined with spatial variation pattern of b value of the seismic risk region for long period.
Zhang Lu , Wang Wei , Wang Shengzu
1993, 15(2):30-35,75.
Abstract:The experimental study on sudden instability processes of the intact Juyongguan granite and Qian' an quartzite specimens and those of Juyongguan granite with saw cuts are carried out at room temperature and solid confining pressures, using the high speed data collecting system with a video-tape recorder. The result indicates that when specimen slides rapidly along its internal oblique fracturing or sliding belt and instability takes place suddenly in the system, the stresses and displacements of different measured points in the testing system vibrate, attenuate, and tend to a new stable terminal state. The whole dynamic process can be divided, in terms of initial motion semi-period of the vibration, into two stages, frictional sliding stage and free vibration one. The synthetic dynamic stress-strain (relative displacement) curves are created from the stress and displacement data recorded. It is also shown that the maximum dynamic sliding displacement is equal or approximate to that of terminal state and the ratio of dynamic stress drop to terminal one is about 1.6.
1993, 15(2):36-41,80.
Abstract:This paper deals with the relationship between great earthquakes and cosmic environment. The statistical results show that the great earthquakes(M≥8)in Chinese continent and its adjacent regions relate evidently to the revolution of the earth and mostly occur at the intervals when the earth rotation speed gets faster; the events in Chinese mainland have some correlations with sunspot activity, conjunction of the nine planets and return of Halley's Comet; ones in West China and its adjacent regions display significant 18.6 yr. periodicity. These correlations suggest that the development and occurrence of great earthquakes are probably influenced by the cosmological environment conditions.
1993, 15(2):42-47.
Abstract:This paper deals with the anomalous features of crust stress change, based on the data observed at Changzhi and Daixian crust stress stations in Shanxi province before the Datong-Yanggao Ms6.1 earthquake. There are not only tendency anomalies, but also short term imminent anomalies. The general tendency is:decline-unbiased-rising. The author made a more accurate short-term prediction before the earthquake, based on the anomalous change of crust stress.
Liu Guangyuan , Liu Xu , Wang Zengjia , Li Shaoye
1993, 15(2):48-57.
Abstract:This paper systematically analyses the state, site condition and other situation of fixed deformation station network in Gansu Province. The observation precision is evaluated by some quantitative indices, and the difference causes and improving measures are presented. The data observed at Gaotai and Lanzhou stations are analysed. And anomalous indices in the data and monitoring ability to mid-strong earthquake of the two stations are also discussed.
Ding Boyang , Lu Taiyi , Zhang Shuqing
1993, 15(2):58-63.
Abstract:Based on the field investigation, the authors divide Shizuishan City into three districts. These districts are situated on seven different morphological types. The varied morphological types correspond with their environments of sediment and erosion. The dynamic features of soils for every morphological type were tested. According to 1 D seismic response spectrum, the average response spectrum for every type was calculated, and the relationship between morphology and response soectrum in Shizuishan City is discussed. Finally, the corresponding design response spectra are given.
1993, 15(2):64-70.
Abstract:Based on the data of 17 earthquakes (M≥8) in China, the author studies the disaster characteristics, destruction types and some countermeasures. The effects of regional site condition, especially the loess and soft soil on disaster are emphasized. It is indicated that for site selection in seismic regions with high intensity, besides the causative faults, it is important to avoid disadvantageous region where the site damages are easily caused; it is necessary to pay attention to asymmetric character of isoseismic contours and the effects of long period vibration on distant site during great earthquakes.
1993, 15(2):71-75.
Abstract:The authors found that fault displacement (D) linearly relates to distance to tip (Ld) which denotes the distance from a certain offset spot to the fault tip, based on the statistics of 40 sets of (Ld, D) out of 24 faults in Northwest Yunnan. At the same time, according to the relationship of fault crush belt width (W) to fault displacement, the fault length (L) might be obtained by maximum width of fault crush belt (Wmax). In this paper, the authors applied the relations mentioned above to quantitatively evaluating the extension toward south of Dingxiling fault as well as the length of Jianchuan fault in Northwest Yunnan.
1993, 15(2):76-80.
Abstract:This paper analyses the geological conditions, seismicity, trend of groundwater, source mechanism of Shiquan reservior area, and considers that the Shiquan Ms4.7 earthquake occurred on Feb. 11, 1978 of the south of Shaanxi province, is induced by reserving water in the Shiquan reservoir.
1993, 15(2):81-83.
Abstract:自1988年11月唐古拉山7级地震及澜沧-耿马7.6与7.2级地震以后,1990年4月26日青海共和发生了7级地震,至今中国大陆已有两年半的时间未发生7级地震了。而同一时期,中国西部周缘地区7级强震却很活跃。
1993, 15(2):84-86.
Abstract:1992年1月23日05时41分,在南黄海北部(35°17'N,121°12'E)发生了Ma5.3级地震。
1993, 15(2):87-88.
Abstract:祁连综合观测台于1990年5月3日建成并正式投入观测。该台设有大地电场、大气电场、电磁幅射和地应力等观测项目,是河西重点监视区内唯一的综合观测台。
1993, 15(2):89-93.
Abstract:目前,在我国相继有不少地震台站(网)研究了适合该地区的测定持续时间震级的方法,并建立了相应的公式。本文利用兰州有线传输台网记录的甘肃及邻区的470个地震资料,建立了6个有线传输台和武威无线传输台网的4个子台的MD震级公式,初步建立了兰州电传台网的MD震级系统。本文还对MD与ML两种震级测量精度做了初步评价,简要分析了放大倍数v对MD震级的影响。
1993, 15(2):94-96.
Abstract:1991年6月13日,舟曲县南峪乡发生山体大滑坡,堵截了白龙江,使河水上涨,公路交通中断,南峪乡政府等4个机关单位和1335间住房被淹。据有关人员现场勘察认为,该滑坡属重力型滑坡,与该地地层结构密切相关,滑坡体顶端的山泉起了推波助澜的作用。
1993, 15(2):97-99,83.
Abstract:在四川地区新的危险区划图的编制工作中,我们根据前人的研究成果和近10年来新增补的大量资料,通过对四川地区现代构造应力场空间分布特征的再研究,对四川地区可能的强震潜在震源区及其未来地震危险性进行了研究。
1993, 15(2):100-110.
Abstract:On the basis of the dispersion relations of MT field, the necessity and applied prospects of the joint inversions using a pair of MT response functions which are correlative with the dispersion relations, are infered. A filter coefficient algorithm is made, with which the corresponding impedance phase data can be estimated using a set of apparent resistivities. The tests for the observed MT data show that when comparing the impedance phase estimated using the dispersion relation with the observed phase, it can be checked whether the dispersion relation between observed apparent resistivity and phase data is satisfied or not, and that the use of the phase data corrected using the dispersion relation in the joint inversion is advantageous to obtain more confident results. It is shown that joint inversions are more advantageous than single parameter inversions, and that in the most case the joint inversion using the apparent resistivities of impedance real and imaginary parts is more advantageous than the joint inversion using the normal apparent resistivity and impedance phase. The existence of the dipersion relations between the ratio apparent resistivity and corresponding impedance phase of the orthogonal electric and magnetic field horizontal components in the frequency EM sounding with horizontal electric dipole(FEMS) are discussed, the better effect of the joint inversion using the pair of EM response functions is obtained. The problems on the one-dimensional joint inversion for the MT and FEMS apparent resistivities, for which the observed frequency bands partly overlape each other, are studied. It is shown that this joint inversion is applicable and effective:the joint inversions of the practical data for two kinds of EM methods at two sites give the results well corresponding to the drilling data. The simulated MT inversions for the data of two kinds of EM methods are made, and more confident results also are obtained.
Sopyright:China Earthquake Engineering Journal