Xing Chengqi , Rong Dailu , Yao Tongfu , Liang Shuxin , Zhang Liguang
1996, 18(3):1-9.
Abstract:Based on the analysis of the geological tectonics setting and deep-seated geophysical characteristics, the causative structure of the Yongdeng MS 5.8 earthquake on July 22, 1995 has been determined by the synthetical study of the faults in the earthquake area, focal mechanism solution, focal depths, meizoseismal region direction, post-earthquake distribution, earthquake fissures and ground motion direction. The tectonodynamic mechanism forming this earthquake has also been approached. It is considered that the earthquake results from the reactivation of the Yaojie-Zhoujiatai buried fault under the direct action of local tectonic stress.
1996, 18(3):10-17.
Abstract:Based on the previous studies,a new mathematical model is established, which is suitable for probabilistic method of predicting seismic intensity in key monitoring area. The sensitivities of the factors affecting prediction to the results are analysed.It is found that the intensity attenuation law plays an even more important role in bringing about the uncertainty. In the light of the principle of uncertainty correction for normal distribution function in seismic hazard analysis, an improved method to correct the uncertainty in intensity prediction is demonstrated and is applied in Hexi key monitoring area. Seismicity period and magnitude interval are taken into account to determine the magnitude-frequency relation. Therefore,the relation secured in this paper may be more accurate.
Liu Guangxia , Zhao Wenjun , Li Zhixiong , Zhang Xian
1996, 18(3):18-24.
Abstract:In this paper, an analysis has been carried out on the problem of the Tertiary Rift Valley Expanding of Bohai Sea based upon gravity-aeromagnetic calculation. Some research results from geothermal heat flow values and the electrical high conductivity layer's upwelling in crust and upper mantle have been referenced in the study. It is considered that there were five big mantle upwellings such as Bozhong, Bohai Bay, Miaoxi, Liaodong Bay and Kenli etc. in the Bohai Sea and its surrounding continent, which formed a group of mantle plumes with clear strike, distinctive shape, big scope and relative assembling character in Cenozoic down warping region of North China due to the deep-seated magma's upmotion.
Min Xiangyi , Wang Tingxuan , Liu Fengxiang , Du Chenghuan
1996, 18(3):25-29.
Abstract:Using the Lanzhou telemetered seismic net digital data, studies the geometric parameters of the sources of Yongdeng aftershocks in Gansu Province and discusses the source mechanism and the 3-D distribution pattern of aftershocks sources. The aftershocks of the Yongdeng earthquake are distributed on two crossed fault surfaces and their origin time has obvious group characters. The epicenter of main shock is just at the point where the two faults cross. The depths of two faults are also different. It is convinced that the source process of the Yongdeng MS 5.8 earthquake belongs to the interlayer-gliding type.
1996, 18(3):30-36.
Abstract:In this paper, the principle and formula of dynamic gap method raised by prof. Qin Baoyan are applied to study the earthquake-generating process and to determine the three elements of earthquake prediction about the Yongdeng MS 5.8 earthquake in 1995. The results are very close to reality.
Zhang Xiaodong , Jiang Zhiping
1996, 18(3):37-41.
Abstract:In this paper, according to Morishita's spatial clustering degree, defined formula of temporal clustering degree and calculated time scanning curves of spatial clustering degree Js and temporal clustering degree Jt before some large earthquakes. The results show that Js and Jt have high value anomaly before large earthquakes. Compared Js with Jt, discussed their features and analysed respective advantage and shortcoming. Obviously, Js and Jt, as an index of seismicity, can be used to predict earthquake.
1996, 18(3):42-47,72.
Abstract:From the angle of earthquake disaster mitigation of the Mogao Grottoes, this paper expounds their seismogeology background and effects of historical earthquakes on them, gives the factors influencing the seismic stability of Mogao caves and their subsidiary buildings, and theoretically puts forward the preliminary prediction method for earthquake damages of the caves and their subsidiary buildings.
Dong Zhiping , Guo Shounian , Jiang Mei , Liu Baoqin , Zhang Liguang
1996, 18(3):48-53.
Abstract:The geotemperature field of upper crust in Tianshui earthquake area is calculated by using finite element method. The results show that basement and fault structures are main factors affec ting shallow geotemperature field in this area.Qilian fold system is a high geothermal anomaly area, whereas Qinling fold system, low geothermal anomaly area. And the fault zone along the north edge of West Qinling mountains is a zone with high geothermal gradient.It is considered that the occurrence of historical earthquakes in this zone is related to thermal stress difference.
1996, 18(3):54-59.
Abstract:In this paper,on the basis of theory of seismic wavelet, regulations of wavelet form variation have been studied in typical fault. It is proved from theory that when seismic waves pass through faults, wavelet form variations are more sensitive than travel time on faults. The results from observation data demonstrate that it is practicable to judge fault properties by seismic wavelet theory.
Yang Liming , Mao Ke , Han Youzhen , Zhu Jianping
1996, 18(3):60-65.
Abstract:In this paper, the factor analysis method to identify the information of earthquake preparation is studied. The results reflect better the evolution process of the information before and after the main shock of the Gonghe earthquake and others. Meanwhile, it indicates that the activity and precursors are different form for distinct stage or same stage to one event, and gives the time mean of each factor. The study has certain practical value for earthquake prediction.
1996, 18(3):66-72.
Abstract:In this paper,based on Type-Ⅲ extreme-value distribuion,the method of parameter estimation is given and point estimation and interval estimation of earthquake prediction are discussed. The prediction accuracy will greatly be improved and the theoretical basis for medium term and long term earthquake prediction is provided.
Lei Tucheng , Ou Bingsong , Huang Lijing
1996, 18(3):73-78.
Abstract:A strong earthquake (M 7.3) occurred in south Taiwan Strait on Sept.16,1994. In this paper,the its structure environment is analysed based on the tectonic unit, active fault, geophysical field, submarine morphology etc. The studies considered that the macroseism is situated at change location from continental crust to transitional crust. The seismicity in history is distributed along modification belt of deep-seated structure. The geological structure,hypocentral depth, type of earthquake, the characters of seismic wave in this region are different from middle and northern Taiwan strait. It has characteristics of the South China Sea system. The spatial pattern of seismicity before the earthquake revealed that the macroseism was result of fault activity along the north margin of the South China Sea system.
He Xiuqin , Niu W ang xiang , Wang Zhen
1996, 18(3):79-83.
Abstract:Analyses the variations of some seismometry indices before the Yongdeng MS 5.8 earthquake on July 22,1995.Finds out obvious anomalies of four indices appeared before the earthquake,which are strengthening of small earthquake activity,background seismic gap,activity belt of small earthquake and precursory seismic swarm.
1996, 18(3):84-86.
Abstract:Analyses corresponding relation between origin time calculated by the two-time method of magnetic storm related to lunar phase and MS ≥ 7.5 earthquakes from Dec.1991 to Nov.1994 in the whole world.During this time,13 MS ≥ 7.5 earthquakes (including a strong aftershock) occurred.Origin time predicted corresponds with 8 earthquakes, 5 earthquakes do not be predicted,5 predictions are failure.
Mao Yuping , Zhou Reiqi , He Wei , Xiang Caiying
1996, 18(3):87-96.
Abstract:Casualties and ground failure caused by earthquakes are major earthquake disasters in Yunnan, their distribution are of obvious regional feature and mainly concentrated in center,northwestern and southwestern Yunnan. The occurrence and distribution range of the casualties and ground failure in Yunnan are related with magnitude and intensity of earthquakes obviously.
Sopyright:China Earthquake Engineering Journal