RUAN Ai-guo , LI Qing-he , ZHAO He-yun
2000, 22(3):209-216,223.
Abstract:The latest development of APE theory for anisotropy study is introduced and applied in electric problem s.In the view of APE cracks modeling,it is believed that when there is no newly developed cracks,the dilatancy and closing of cracks balance each other.Using a new electric conductivity anisotropic model (named cubic model),put forward by present authors,for the cracked rocks containing fluid,the mechanism of earth resistivity precursor of earthquake is discussed according to the APE theory,considering the variation of aspect ratio to be the main source of the precursor due to stress change.It is concluded that the increasing or decreasing variation of earth resistivity with large amplitude before strong earthquakes could be explained easily by the new electric anisotropic model,even if the total porosity or strain do not change or there are no new cracks developed.Moreover,it is found that resistivity variation characteristics are related to the aspect ratio and distribution of cracks.But the conclusions from the discussion in this paper are effective only for seismic field precursor,not for source precursor related to new developed cracks.
YAO Lan-yu , NIE Yong-an , ZHAO Gen-mo
2000, 22(3):217-223.
Abstract:A complete suit of closely analytical expressions of stress field is presented for the dip-slip shear fault with an arbitrary dip angle in a semi-infinite medium.Checking and reviewing the analytical expressions of stress field by other researchers,closely mathematical reasoning for the expressions is done again,thus this suit of expressions has become more perfect and reliable.
2000, 22(3):224-231.
Abstract:The microtremor characteristics of 3 tall buildings in Hexi Corridor,Gansu province are analyzed.The characteristics of their vibration period,damping ratio and mode sharp are analyzed.Considering the site conditions and seismic situation of the reg ion,some main problems which should be taken notice in future aseismic design of tall building in Hexi Corridor are proposed.
LIU Hong-chun , DAI Hua-guang , LI Long-hai , JIA Yun-hong , YANG Rong
2000, 22(3):232-235.
Abstract:The macroscopic epicenter,the intensity distribution and the geological background of the 1954 Minqin MS7.0 earthquake are analysed and studied.The range of the meizoseismal region and the seismogenic fault has been decided at the first time.The earthquake resulted from the extend of the Hongyashan-Sidaoshan fault towards the east with left-lateral and inclined up ward slip under the NE or NNE main compressive stress and related to action of the NNW tectonic zone at the same time.
WANG Yong , ZHANG Guo-hong , DAI Jian-hua , DUAN Li-xin
2000, 22(3):236-240.
Abstract:Basic condition of geotemperature observation of Chang ping seismic station and normal change of geotemperature by the station are introduced.Characteristics of anomalous geotemperature change before some earthquakes are analysed.The results show there are 9 ones to correspond to earthquakes occurred in a range of 300 km distant from Changping station among 11 anomalies in geotemperature data by the station since 1995.Anomalous shapes before earthquakes near by and distant the station are trend drop-rise and sudden jump respectively.The larger the anomalous amplitude and the longer the quiet time,the larger the magnitude of coming earthquake.The anomalies in geotemperature data observed once a minute are more obvious than that observed once an hour.
LIU Yuan-sheng , LIU Gui-he , TONG Feng-lan
2000, 22(3):241-246,257.
Abstract:Anomalous characteristics of observation data of 6 wells in Liaohe oil field before the Xiuyan MS5.6 earthquake,Liaoning on Nov.29,1999 are analysed.Observed items are groundwater level,oil recovery volume,casing pressure and gas recovery volume.Trend,short term and impending anomalies appeared in observation data of the 6 wells before the event with fairly good synchronism and a shape of rise-fall-rise.The test shows disturbance factors,such as water flooding,pumping water,atmospheric pressure and temperature etc.have not influence on the observation data,therefore,the anomalies can be believed.
SHAO Yong-xin , LI Jun-ying , LI Yi-bing , TIAN Shan
2000, 22(3):247-250.
Abstract:Observation data of radon in groundwater of 36 wells in northern part of North China are used to study the evolution processes of radon anomaly before the Tangshan MS7.8 earthquake taking per half year as scale.The results show anomalies of the radon in groundwater progressed from outer ring to epicentral region and anomalous pattern changed from complicated to simple before the earthquake.In the short impending stage,strong anomaly region was formed at Tangshan area.After the earthquake,the anomalous pattern dispersed and normally recovered.
LIU Hong-gui , GU Jin-ping , WANG Zheng-zheng , NAN Jin-sheng , MA Jian-jun
2000, 22(3):251-257.
Abstract:According to the definition for the spectral magnitude advanced by Duda and Nortmann,using the digital vertical displacement data recorded by 5 telecontrol stations in Jiangsu area and 13 groups of 0.5-octave band-pass filters of which central period are 1.2 s,1.0 s,0.67 s,0.4 s,0.25 s,0.147 s,0.119 s,0.1 s,0.078 s,0.065 s,0.054 s,0.047 s,0.041s respectively,the average velocity spectra of P and S wave of 54 earthquakes has been determined.And the synthetical fact f of each earthquake can be gotten.Change feature of corner periods of the velocity spectra of P and S wave and the f values with time are studied.The results show that the synthetical fact f of velocity spectrum of medium-minor earthquakes changed from high to low with time during one year or shorter period before medium-strong earthquakes which occurred in the duration of low f-value.
YANG Zhan-bao , ZHOU Bin , ZHANG Ying-kai , WU Chun-hua
2000, 22(3):258-260,272.
Abstract:Basic conditions of Zhuanggu-25 well in Shengli oil field are introduced.Change characteristics of oil output before earthquakes and reflecting earthquake ability of the well are analysed.The results show that oil output of the well suddenly rose with gush sometimes before earthquakes.The larger the magnitude,the larger the anomalous amplitude and the longer the lasting time of the anomalies.Various degrees of anomalous changes of oil output of the well appear before most ML ≥ 4 and ML≥ 5 earthquakes in a range of 200 km and 500 km distant from the well respectively.Mechanism of reflecting earthquake of Zhuanggu-25 well is discussed in last.
2000, 22(3):261-266.
Abstract:Following shocks of earthquakes (MS≥ 5.0) of Chinese continent are studied.The following shocks can be divided into three types:residual,induced and newborn,according to mechanism of the events.The mechanism and major feature of the following shocks and its significance in study of seismogenesis and in prediction of earthquake trend after major earthquake are discussed.
2000, 22(3):267-272.
Abstract:The hydrogeology and engineering geology settings of the area of Daqiao reservoir and its dam,Mianning,Sichuan province are analyzed.It is believed that after the store water,water of the reservoir may penetrate down due to a lot of faults in the areas,therefore,there is a very fair possibility of induced earthquake.The possible area for induced events is at the middle portion of the Anninghe fault.The hill-slopes around the reservoir are relatively stable,but the possible instable situation of a few localities of hill-slopes near the reservoir exits,which have to be attached importance to although do not affect the function of the reservoir.
ZHANG Min , ZHANG Qi sheng , XU Qin
2000, 22(3):273-278.
Abstract:It is proved Gonghe basin is not low intensity zone by the 1990 Gonghe MS7.0 earthquake and traces of palaeoearthquake in the basin.It's seismic risk should not be ignored.Based on a large number of studies,geologic background of the Gonghe earthquake is analysed and seismogenic process of the event is discussed.The result shows that development period of the event is about 20 years and can be divided into 4 stages,that is,long term,medium term,short term and impending term,reflecting the process from elastic deformation,ductile deformation,harding strain to precursory creep of crustal medium.
2000, 22(3):279-283.
Abstract:Geological and hydrological conditions of Longyangxia reservoir region are analysed.Relationship between the Gonghe MS7.0 earthquake,1990 and water storage process of the reservoir is studied.The results show that distribution of main shock and strong aftershocks in Gonghe MS7.0 earthquake sequence with time,changes of precursory field,deformation field and some seismometry indexes are related to the water storage process and change of water level of the reservoir,being similar to typical reservoir earthquakes.It is proved that the Gonghe MS7.0 earthquake is induced by the Longyangxia reservoir and is an induced tectonic earthquake.
SHAO Yong-xin , LI Jun-ying , LI Yi-bing , TIAN Shan
2000, 22(3):284-287.
Abstract:Relationship between the dynamic anomalies of groundwater in northern part of North China as well as dynamic anomalies of oil wells in Liaohe,Dagang,Shengli and Huabei oil fields and local structures is studied.The results show anomalous shapes of groundwater and dynamics of oil wells before earthquakes are not only related to the regional structures,but also closely related to local structures.The anomalies are positive in upheaval area and are negative in depression area.
WANG Zhou-yuan , HE Shao-lin , LI Yong , JI Feng-ying
2000, 22(3):288-295.
Abstract:The distribution feature of intermediate and deep focus earthquakes(M≥ 6.0) in China and relationship between it and seismic activity in whole nation and the main seismic areas of China are analysed. The deep focus events are distributed in Northeast China, concentrated in a region of 2×2° of which central point is 42° N, 130°E. Average depth of the events is about 560 km. The intermediate shocks are distributed along a zone of which strike is NE~SW from the East China Sea, through Taiwan to Dongsha Islands, with depth within 250 km and a mean value near 150 km. There is a period about 63 a in activity of the intermediate and deep focus earthquakes in China. The activity of the intermediate shocks of Southeast China comes after the deep focus shocks of Northeast China. After intermediate and deep focus earthquakes, MS≥ 7.0 shallow earthquakes of Taiwan region and MS≥ 6.0 shallow earthquakes of northeast Qinghai Xizang block may occur. The seismic activity of Qinghai Xizang block generally begins in northern part first, then migrates progressively southward along the eastern part of the block. After shallow earthquakes controlled by the eastern stress field and intermediate and deep focus earthquakes quieted for about 20 a,the Huichun M7.0 deep focus earthquake and the Taiwan M7.6 earthquake may be a signal of aggravation of action of the Pacific plate and beginning of relative seismic activity in China.
YUAN Dao-yang , YANG Bin , ZHOU Jun-xi , YAO Zeng , ZHANG Xiang-hong
2000, 22(3):296-300.
Abstract:The results surveying non-visible faults at east and west sides of Qinwangchuan basin and the comparison of terraces of rivers in the region indicate that the basin was formed in Neogene and became a close fault basin in late period of mid-Pleistocene by the compression and thrust of faults at east and west boundaries of the basin.The Jinqianghe river and Heimajuanhe river flow ed across the Qinwang chuan basin to the Yellow river along the ancient river course of two sides of the basin from late period of mid-Pleistocene to early period of late Pleistocene and a thick layer of alluvial and diluvial sand-g ravel was formed in the basin.The basin became an arid one from late period of late Pleistocene to early period of Holocene by continuous rising of Pingcheng basin and change of the river bed.
2000, 22(3):301-305.
Abstract:Surface fault width caused by strong earthquake is studied.The result shows earthquake (MS=6.6) is minimum magnitude of producing surface fault,and earthquake (MS=8.5) may produce fault zone with width of 100 km.It means,for the very strong earthquake,the surface fault is stringy rupture,isn't lineal rupture.An empirical formula between surface fault width of earthquake and magnitude is obtained.
2000, 22(3):306-310.
Abstract:On the basis of the theory of elastic crack,the reflecting earthquake effect of well water level in the confined aquifer is studied by using numerical simulation method.The simulated results demonstrate that the confining condition of well-water bearing system has heavy influence on reflecting earthquake effect of water level change,and the observation quality is directly affected by the leaking level on the sides of aquifer and the height of water head.When the system is confined well,the change of observation water level has a linear relation with water head change.Moreover,for earthquake prediction purpose,in a good well-water bearing system the good penetrability is also one of the important factors to affect water level change,it is effective if the system has a high penetrability.
LIU Yuan-sheng , ZHANG Zhao-dong , LI Ji-xun , YIN Zhi-qing , ZHOU Bin
2000, 22(3):311-316,324.
Abstract:On the basis of theory of elasticity and dynamics of ground fluid,effects of oil recovery and water flooding on dynamic of oil wells in oil field are analysed by horizontal layered oil-bearing formation model.It is discovered tha changes of stress and strain of the oil-bearing formation by oil recovery in other layer and water flooding resulted in change of pore pressure in the oil-bearing formation,which effected change of dynamic of oil wells.
Zhan bao , YIN Zhi-qing , YOU Shao-yan , ZHANG Zhao-dong
2000, 22(3):317-320.
Abstract:General situations of 21 wells for observing dynamic of underground water and oil are introduced.The observation well net had adjusted in 1998,some wells are stopped observation and some wells are newly built,for strengthening seismologic surveillance of the Bohai sea and its surrounding area.The new principles selecting wells and the condition of observation well net adjusted are introduced.A preliminary analysis on reflecting earthquake ability of the net is made.It is considered the reflecting earthquake ability of the net is stronger.The oil output of some wells suddenly rises before earthquakes which occur in process of oil output change from high value to low value or after the oil output returned to normal.
LIU Yuan-sheng , ZHANG Zhao-dong , ZHU Jian-ya , WANG You-pei , HAN Hai-hua
2000, 22(3):321-324.
Abstract:On the basis of model of ideal horizontal layered oil-bearing formation,a preliminary study on mechanism of dynamic change of oil wells before strong earthquake is made.Pressure of poro-fluid in oil-bearing formation changes by stress and strain in the crust.The pressure of poro-fluid is increased with increase of stress in the crust,then changes of oil output and gas output of oil wells are caused.
YIN Zhi-qin , YANG Zhan-bao , ZHANG Zhao-dong , YOU Shao-yan
2000, 22(3):325-328.
Abstract:Anomalous characteristics of dynamic of oil wells in Shengli oil field before the 1975 Haicheng MS77.3 earthquake,the 1976 Tangshan MS7.8 earthquake and the 1989 Datong MS6.1 earthquake etc.are analysed.Relationships between anomalous changes of dynamic of oil wells and origin time,place and magnitude for a coming earthquake are studied.Anomalous amplitude of ratio between oil and gas is larger than that of oil output of oil wells.The larger the anomalous amplitude,the larger the magnitude of coming earthquake.The shorter the epicentral distance,the larger the anomalous amplitude.The anomalies before earthquakes distant from the oil wells is a shape of sudden jump.The anomalies before earthquakes near by the wells arise more early with a complicated shape,which can be divided into early term trend change,mid-term vibrant change and sudden jump before earthquake in the main.Finally,mechanism of the anomalies is discussed.
LIU Yuan-sheng , Zhang Zhao-dong , CUI Gui-mei , WANG Zhong-min , Dong Chuan-fu
2000, 22(3):329-332,342.
Abstract:On the basis of the theory of elasticity and hydrokinetics,effect of tide-generation force on dynamics of oil wells is studied refering to the theory of earth tide and by using model of horizontal layered oil-bearing formation.A method inverting stress in oil-bearing formation by tidegeneration force is given.The stress drops of two earthquakes are calculated by the method.The results by the method approach results by other methods.
ZHOU Bin , ZHANG Ying-kai , LI Ji-xun
2000, 22(3):333-337.
Abstract:Characteristics of geological structure,geophysical field and seismic activity of the Bohai Sea and its vicinity are analysed and studied.The results show three groups of fault of NNE,NW and NWW developed in the region.The Tan-Lu fault of NNE is divided into three section by faults of NWW.The seismicity is the strongest in the middle section among them.Three M≥7 earthquakes and three M≥6 earthquakes occurred in the section.The earthquakes are distributed along two belts,forming the Tan-Lu seismic belt and Yanshan-Bohai seismic belt.In the middle part of the Bohai Sea,the values of heat flow are the highest,the Moho discontinuity and the Conrad discontinuity have risen,depth of the low-resistivity layer of the upper mantle is 30~50 km,being mo re shallow.
LIU Yuan-sheng , HU Jiu-bo , ZHANG Zhao-dong , CUI Gui-mei , ZHANG De-yuan
2000, 22(3):338-342.
Abstract:The quantitative relation between liquid output of an oil well and pressure at the mouth and the bottom of the well is studied by using the theory of hydrokinetics.The relation exchanging liquid output of the oil well for the pressure at the mouth of the well equivalently is given.The processing method for observation data of oil well dynamic is studied further.Taking Dong shui-3 well in Shengli oil field as an example,processing of observation data of the well is made and effect of radius of outlet pipe on flow of the pipe and equivalent water level is studied.
2000, 22(3):343-345,348.
Abstract:The application of serial communication technology in seismic information transfer is briefly introduced,such as modes of serial communication,RS-232 standard adapter and modem.The form of real time serial transfer of seismic data is described.
2000, 22(3):346-347.
Abstract:Frequency spectra of Tianzhu earthquake sequence are analysed by using the fast fourier transform and the maximum entropy spectrum methods and results by the two methods are compared.The results show the two methods are effective and reliable for obtaining useful informations from seismic wave.The resolving power of M EM is higher than FFT,but the FFT is a simple and convenient method.
WU Qi-min , MAO Sen-lin , LIU Dong-sheng , GOU Ya-jiang , CHEN Lan-xin
2000, 22(3):348-350.
Abstract:According to records of 338 earthquakes in recent years by SK seismograph of Tianshui seismic station,a formula of relationship between travel-time difference of maximum surface wave from primary wave and epicentral distance is given by least squares method.It is discovered there is much difference between epicentral distance calculated by using the J-B travel-time table and that of practical observation,the difference is small by using the formula and travel-time table of this paper by comparison.
Sopyright:China Earthquake Engineering Journal