1999, 21(3):225-233.
Abstract:The states of local seismic activity and seismic tendency have been studied by using time progress analytical method to the historical seismic data in Gansu and Shanxi region.The results are as follow:(1) The active and quiet periods of local strong earthquakes with MS7.0 have occurred alternatively in different time scales.(2) In the active periods of strong earthquakes with MS≥ 7.0,the activities of moderate strong events have accompanied the occurrence of strong earthquakes with MS≥ 7.0,but they have accompanied the occurrence of earthquakes with MS6.0 or have occurred as cluster of events with MS≥ 5.0 in the quiet periods.(3) The seismic states of Gansu may be in the quiet period of both strong earthquakes with MS7.0 and moderate strong earthquakes,and the probability of occurrence of strong earthquakes with MS≥ 7.0 is small within one or serveral hundred years,meanwhile,the probability of occurrence of moderate strong events is also small over ten years from now.
WANG Wei , SONG Xian-yue , LIU Zheng , WANG Zheng-zheng
1999, 21(3):234-241.
Abstract:The seismicity factor A-value is defined by synthesizing the seismicity precursors in time, space and magnitude. The seismicity data of moderate or small earthquakes during 1972~1996 in northern China are used in spacial scanning of seismicity factor A-value, studying mid-short term change of the A-value before the earthquakes. The result shows that in mid-short term, the midterm anomaly zones of A-value that appeared about 2~3 years before a lot of strong earthquakes may contract or disappear obviously, and the zones may obviously extend again about 1~3 months before some earthquakes. Some problems about mid-short term earthquake prediction by using the A-value are also disscused.
SHI Yu-cheng , CAI Hong-wei , XU Hui-ping
1999, 21(3):242-247.
Abstract:The uncertainties from current site earthquake response analysis are analyzed and a method for solving the uncertainties of system parameters by using the Monte Carlo simulated method is presented. Some results using the proposed method are given and the effect of parameter uncertainties on reliability of earthquake response analysis is discussed. It is suggested that to estimate the input parameters by means of shochastic theory is necessary. It has been proved that the proposed method is advantageous both in computing efficiency and precision.
LIU Xi-qiang , ZHOU Hui-lan , ZHENG Zhi-zhen , SHEN Ping , YANG Xuan-hui , LI Hong
1999, 21(3):248-253.
Abstract:Wavelet packet transform is further expansion of wavelet transform theory. Signals may be decomposed into different frequency section by wavelet packet transform method. Emulation study results show that wavelet packet transform has a series of good characteristics while other analysis methods do not have. The method is a very effective filtering method.
FAN Liang-ben , DING Bo-yang , ZHU Yuan-lin , ZHANG Ying
1999, 21(3):254-258.
Abstract:The Green function on two-phase saturated medium by concentrated force is given and the wave field is discussed according to a Biot equation.
DAI Hua-guang , CHEN Yong-ming , SU Xiang-zhou , LIU Hong-chun
1999, 21(3):259-267.
Abstract:According to data of field geological investigation,geometry and kinematics characteristics of Tianqiaogou-Huangyangchuan active fault zone since later Pleistocene are described in detail.The fault zone may be divided into Tianqiaogou segment showing inverse left lateral strike slip nature and Huangyangchuan segment showing normal left lateral strike slip nature.Main active period of the fault zone is Pleistocene and its slip rate is 4~5 mm/a.In early Holocene,its active strength gradually became low,and the latest palaeoearthquake on the fault occurred 0.759×104~1.02×104 years ago.
WU Fu-chun , ZHANG Hong-fu , JING Bei-ke , DUAN Feng , ZHANG Yi-min
1999, 21(3):268-273.
Abstract:Some special aseismic precursory anomalies obtained from Shaanxi precursory network are presented. Analysing the cause of these anomalies, following views are got:the two anomalies of groundwater level of Shuangwang well, Weinan in 1986 and 1996 may be caused by the flood peaks of the Weihe River;the big anomaly of ground tilt observed from Hancheng station in 1977 had relation to the level of the Yellow River;the anomaly of ground tilt observed from Ankang station in 1983 was due to the big flood in Ankang area in that time;the two big anomalies of groundwater level of Sanyuan well had relation to water storage of Fengcun reservoir.
WANG Yong , LIU Fu-sheng , ZHANG Guo-hong , ZHANG Xue-zheng
1999, 21(3):274-279.
Abstract:The anomalous changes in data of borehole strain measurement at Changping station before the Zhangbei-Shangyi MS6.2 earthquake on Jan. 10, 1998 are analysed. The results show that trend anomalies in the data before the earthquake are obvious. Continuous time of the anomalies of body strain has a good relation to the mag nitude. The short-term and imminent anomalies in differential strain data have arisen. Orientation of principle strain calculated from linear strain data turned gradually towards the epicenter before the earthquake. The relationship between the anomalous changes of tide factor in body strain data and the earthquake is studied.
ZHANG Yu , ZHU Wu-quan , CHANG Qian-jun , ZHOU Zhi-yu
1999, 21(3):280-284.
Abstract:Observation data of water tube tiltmeter with type FSQ of Tanchang station from 1990 to 1998 are analysed. The results show that observing accuracy of tide response function is in the observation standard. Influence of hydrologic and meteorological factors on observation data is obvious. Short-imminent anomalies in a certain ex tent in the observation data of Tanchang station appear before earthquakes with magnitude of 4 or so in the vicinity of the station and trend anomalies appear before mid-strong earthquakes within a distance from the station.
1999, 21(3):285-295.
Abstract:Data of 6 profiles in E-W and 2 profiles in N-S by MTS in the northern segment of North-south seismic belt are compiled. The electrical structure of crust and upper mantle of the area is comprehensively studied. Some questions in the data are discussed.
CHAI Chi-zhang , LIAO Yu-hua , ZHANG Wen-xiao , MA He-qing
1999, 21(3):296-301.
Abstract:Section of 5 test grooves and landforms of scarps along fault at eastern piedmont of the Luoshan Mt.are analysed and studied comprehensively. It is showed that a few young scarps with free surfaces along the slopes of eastern piedmont of the Luoshan Mt.are backside walls of gravity landslides,with no relation to the fault motion. The time before present of the last rupture event along faults at the eastern piedmont of the Luoshan Mt. is (2 105±175)a. The occurrence probability of MS ≥ 7.0 earthquakes along the fault in future 50 year is estimated.
1999, 21(3):302-309.
Abstract:The basic characteristics of earthquake rupture of intraplate reverse fault and sign of its segmentation have been discussed in detail based on the type and size of surface rupture, tectonic environment, geometric form,kinematics character, as well as the aftershock distribution patterns for 16 intraplate earthquakes produced by reverse fault in the world wide.The result shows that earthquake ruptures of reverse fault are different from that of strike slip fault and normal fault. The rupture size along the strike for reverse fault is much more short, and the rupture pattern often has a two dimensional plane distribution. The seismic fault does not show on the ground or only part of seismic fault shows on the ground. The earthquake ruptures of reverse fault are still complexer than that of the strike slip fault and normal fault in the mechanics character of an individual fracture and the geometric structure.
WANG Jian-rong , ZHANG Zhen-zhong , WANG Jun , LI Lan
1999, 21(3):310-314.
Abstract:Influence of vibration frequency on dynamic constitutive relationship of loess is studied under uniform sine loadings with 4 kinds of frequency. The results show dynamic constitutive relationship of loess for 4 kinds of frequency submits to hyperbolic equation. The test constant a and b decreases with increase of vibration frequency. The effects of vibration frequency on parameters of the hyperbolic equation, elastic modulus, shear modulus, dam ping ratio are discussed.
CHEN Yong-ming , LIU Hong-chun , ZENG Wen-hao , LIU Hong-mei , ZHANG Wei , DAI Hua-guang
1999, 21(3):315-320.
Abstract:Based on field investigations and interpretative result from air photos,the main geological disasters including the seismic rupture zone,the seismic landslides and the seismic fissures,and their distribution of the 1927 Gulang MS8 earthquake are described.Then,the characteristics and controling factors of destruction of this earthquake are studied.The result shows that the surface destruction of the earthquake is obviously affected by the geography and the types of rock and soil.
1999, 21(3):321-325.
Abstract:Daily change characteristics of hour by hour value of ground resistivity observed at Lanzhou geoelectric station are analysed. The results show that a stabler background value exists in mean daily change of hour by hour value a month or a year of ground resistivity. The background value can be regarded as a basis judging short-impending anomaly of daily change of hour by hour value of ground resistivity.
1999, 21(3):326-330.
Abstract:Using data of mobile gravity measurement, variation features of gravity field in south area of northern segment of the North-south seismic belt is analysed. The results show that using 105°E as a boundary, gravity field variation of the east side of the boundary is different from that of the west side of the boundary, reflecting there is a NS active tectonic zone in deep crust along 105°E. In Gansu province, three MS ≥ 5 earthquakes occurred since 1990. Before the three earthquakes, anomalies of gravity differences of Anmencun, Lanzhou and Shuping, Yongdeng observation sites are obvious.
LI Zhong-hua , SU You-jin , CAI Ming-jun , ZHANG Jun-wei , LIU Zu-yin
1999, 21(3):331-333.
Abstract:Earthquake sequences in which mag nitude of main shock is over 4.9 since 1965 in Yunnan area are selected. According to spatial distribution of early aftershocks of 51 earthquake sequences, data of source rupture length are obtained. The empirical relationships between magnitude and source rupture length are calculated by least squares linear regression model. The results of this paper is useful to analyze seismic hazard in Yunnan where shallow-focus earthquakes often take place.
1999, 21(3):334-336.
Abstract:Anomalous characteristics of groundwater level of 5 observation wells in Inner Mongolia before and after the Zhangbei-Shangyi MS6.2 earthquake are analyzed. By using the multilayer tracing prediction method, testing forecast to the MS6.2 earthquake are made, studying relationship between the earthquake and water level high value anomalies. Effect of the test is better and the anomalies is a precursory reflection of the earthquake.
1999, 21(3):337-339.
Abstract:Observation data of P-C type strainmeter at Xichang seismic station from 1995 to 1997 are processed by using a new method in fruit of the Eighth Five-year Plan Period. Short-term and impending anomalies before the Wuding MS6.5 and Lijiang MS7.0 earthquakes etc. are obvious in processed observation data.
SUN Shi-qing , ZHANG Yu-fang , WANG Jing-bo
1999, 21(3):340-342.
Abstract:Anomalies of radon content in ground water, ground water level and ground resistivity observed by some stations in Pingliang area, Gansu province before the Haiyuan MS4.7 earthquake on July 29, 1998 is analysed and prediction to the MS4.7 earthquake is introduced. The results show it is better that some observation items of Pingliang area reflect earthquakes with magnitude of 5 or so in Pingliang area and Xiji-Haiyuan-Guyuan area and MS≥ 6 earthquakes in northern segment of NS seismic belt.
WANG Ting-xuan , FAN Wu-ji , WANG Xian , BA Zhi-ping , ZHANG Hui-fang
1999, 21(3):343-344.
Abstract:Influence of computer reckoning by time in 2000 on seismic observation is analysed. The methods solving the problem are proposed.
Sopyright:China Earthquake Engineering Journal