Abstract:On the basis of the hard inclusion earthquake preparation model (HEPM for short) and referring intraplate earthquake preparation characteristics and geologic structure feature of North China,model of crustal structure of four layers with a hard inclusion,a soft inclusion and a vertical fault is constructed. Dynamic simulation on the space time distribution of deformation and stress fields near surface for the model is carried out. The results show that at beginning of earthquake preparation, deformation near surface of the hard inclusion in the model is relatively stable, a deformation gap is showed. During the medium short term period before earthquake, the deformation increased swiftly. Meanwhile, the average stress in the region strengthened obviously,which is the inner mechanism for migration of precursory anomalies with regularity from outer area to epicenter area of strong earthquake.

Abstract:The harmonic analysis results of data by the YRY 2 bore hole earth strain meter of Tai an seismic station from 1991 to 1996 are introduced.The dynamic characteristics and stability of the tidal parameters for the meter are analysed. A comparison between the results of the YRY 2 meter and SSY Ⅱ quartz tube extensometer is made. The discrete error mean square of NS channel of the YRY 2 meter is 3.3%, that of NE channel of the meter is 3.6%, and monthly discrete error of phase lag is less than 2.0°. It shows the observation precision of the YRY 2 meter of the station is analogous to the best SSY Ⅱ quartz tube extensometer.

Abstract:Variation features of geotemperature in the depth of 10 m by Gaoling observation point before the Jingyang M_S4.8 earthquake on Jan. 5, 1998, Shaanxi province are studied and analyzed. The geotemperature fell continually in 1997. The geotemperature rose suddenly from Dec. 15, 1997, especially in 15 days before the event and returned to normal after the event. Geotemperature variation in the depth of 10 m by observation point of high pressure switchgear plant of Xi'an city is the same as that by the Gaoling point. It is believed that rising variation of the geotemperature by the Gaoling point is the anomaly before the Jingyang M_S4.8 earthquake.

Abstract:On the basis of analysis of observation data for mercury content in Songshan spring of Yanqing county, Beijing city, reflecting earthquake ability of mercury anomaly of the spring is studied and evaluated.The results show that there is a better correspondence between mercury anomalies of the spring and earthquakes. Especially, there is obvious correspondence between the anomalies and mid small earthquakes near the spring and M_S ≥5 earthquakes far away the spring since 1997. The cause of sensitivity reflecting earthquake for the anomalies of the spring is discussed from activity of geological structures around the spring.

Abstract:The space evolution process of ground fluid anomalies before five medium strong earthquakes of northern part of North China is systematically studied. The anomalous migration feature is analyzed. On the basis of the migration feature as well as relation between anomalous time and epicentral distance, five signs and three steps for predicting risk region of strong earthquake are given,which are tested by three earthquakes. The results show it is possible to predict risk region of coming strong earthquake to a certain extent by using space evolution features of ground fluid anomalies.

Abstract:Autocorrelation coefficients of data of geomagnetic total intensity of neighboring periods from six stations in Henan province are calculated respectively. The relationship between the coefficients and earthquakes is analysed. The results show there is a good correlation between them.The original time is usually within 1~8 months after the lowest value of the coefficients.Empirical formulas between magnitude,anomalous area of the autocorrelation coefficients and epicentral distance for every station are statistically obtained. By using the empirical formulas of three or more stations and intersection method, the magnitude and epicenter of coming earthquake can be forecasted. The test results show the method is basically feasible.

Abstract:The types of sequences and features of foreshock and aftershock activities of 18 M_S≥5.0 earthquakes since 1970 along Qilian-Haiyuan seismic zone are studied.The space distribution of types of the sequences along the zone is analyzed.The results show that 44 percent of events are mainshock type,and 55 percent of events are isolated type. The sequences in Xiji-Haiyuan-Guyuan segment of the zone are isolated type, that in the middle eastern segment of the zone are mainshock type, that in the middle segment of the zone are isolated type and mainshock type both, and that in the western segment of the zone are isolated type. The result of the seismicity trend judging after the Jingtai M_S5.9 earthquake on June 6, 2000 by using study results of this paper consists with real facts.

Abstract:The variation features of synthetic focal mechanism solution of small earthquakes before mid strong earthquakes in south Ningxia region are studied.It is found that direction of the P axes drifted off average values and turned to E or SE,being accompanied by identified first motion mark of P_n and P_g waves of small earthquakes. The focal mechanism solutions of 6 mid strong earthquakes in south Ningxia region show that the earthquakes occurred under the affect of principal compressive stress of NE, with no somewhat change in comparison with direction of principal compressive stress of regional stress field. So the possibility of the destructive earthquakes to occur in the region is smaller. But patterns of seismicity in recent years show it is possible that seismicity is going to concentrate in Zhongwei, Zhongning and Tongxin region in the future.

Abstract:Based on the "focus trigger system response" seismogenic model,the time space evolution characters of seismicity pattern before and after group strong earthquakes in Xinjiang region from 1996 to 1998 are discussed and analyzed. The signal inducing earthquake is defined. The relation between the signal inducing earthquakes and succeeding strong earthquakes is studied. The results show that the medium earthquake activity area that is triggered by strong earthquake and its border may be a dangerous region of future strong earthquake.The signal inducing earthquake within two days after the strong earthquake or its strong aftershock has forecast significance. There is a very fair possibility of strong earthquake with magnitude larger than that of the signal earthquake by 0.5~2 to occur in range of 200 km around the signal event within 3 years after the event. Finally a preliminary discussion on the mechanism of group strong earthquake activity is made.

Abstract:The earthquake trend of Kuma fault zone after the Henan M_S5.1 and the Maqin M_S5.0 earthquakes is analyzed and discussed on the basis of seismicity,anomalous changes of coda lasting time by Dawu seismic station and radon contents in groundwater by Changning, Huangyuan and Xining stations. The results show that there is an obvious corresponding relation between mid strong earthquakes in Henan-Maqin area and strong earthquakes along Kuma fault zone. There is a gap by M_L≥3.0 earthquakes at middle section of the Kuma fault zone. Anomaly of the coda lasting time still exists and the trend anomalies of radon content in groundwater still continue.Therefore, there is a background of strong earthquake along the Kuma fault zone after the two arthquakes.

Abstract:The space distribution characteristics of structures from topography and landform of the south part of Ordos block and Weihe basin are analyzed.It is considered that three dimensional cross structures are formed by three NW upwarpings of the south part of Ordos block and EW subsidence centers which range obliquely as well as cross uplifts among them in Weihe basin.The space distribution of historical and modern earthquakes in and surrounding the Weihe basin shows that three dimensional cross structures have a strong dominion on seismicity in the basin.

Abstract:On the basis of field investigation and former studies,the geological structures and seismicity in Xiaolangdi reservoir and its adjacent area are analysed.It is considered that the geotectonic background is complex and seismicity is relatively week in the area. By using probabilistic statistic method, logic information method and gray cluster method, possibility and magnitude of induced earthquake of the Xiaolangdi reservoir are forecasted.The result shows that there is the possibility of the induced events,especially in the middle segment of the reservoir and the maximum magnitude could be 5.0.

Abstract:Dynamic change process of stress field of north China before and after the Tangshan M_S7.8 earthquake is inverted by using the method inverting stress change of deep layer of the crust by reference[2] and data of well water level.Dynamic change characteristics of the stress field are analyzed.The results show anomalous region with stress decrease was produced in epicenter region and its vicinity two years before the earthquake. The anomalous region expanded outward and anomalous amplitude increased before impending the earthquake.The anomalous region contracted and disappeared gradually after the earthquake.

Abstract:The necessity of establishing a 3d/2d model is discussed. Owing to introducing the model, the full electric and magnetic field galvanic distortion tensor is simplified. The effects of a surface 3 d conductivity anomaly on a regional 2 d structure is derived by comparing data through Swift rotation with data through Bahr decomposition, then is expressed by a distortion matrix. The effect of a local anomaly can be separated from a regional structure by researching and decomposing the distortion tensor matrix. So it is available to find out the regional structure dimensionality, classification of the local structure and the effect of it on the regional structure. Eventually, the simple distortion decomposition method is tested through three sites of practical data.

Abstract:In the process to transform analog seismogram into digital data by using computer scanners,the seismogram image is detrended according to slope of horizontal baselines on original records. A median filtering technology is used to further improve image quality and seismic waveforms are adaptively retrieved by an image segmentation method. The method for correcting slope and image segmentation technology are introduced.

Abstract:By using soniscope, the wave velocities in depth of 0 to 1.5 m of seasonally frozen ground at four geomorphic units in Lanzhou are obtained during the winter and the soil density, moisture content and ground temperature are measured respectively. Relations between the wave velocity and the cementation of soil, ground temperature and moisture content are analyzed. The results show that the cementation of soil has an important effect on the wave velocity. The better the cementation of soil, the greater the wave velocity. When the temperature of soil is above 0℃, wave velocity decreases with the increase of moisture content. When the temperature is below 0℃, wave velocity increases with decrease of the temperature of soil.

Abstract:Types of hydrogeochemical anomaly are influenced by age of groundwater,which is an indirect parameter of intense degree of water rock reactions.The younger water, which means the water cycles underground in a short period, will not well reflect the changes of geochemical environment in crust, while the older water will not reflect the changes in time. From study of this paper, the following results are obtained:(1) The younger water or the older water often show the short impending changes. (2) Changes of geochemical elements in the middle age water show the long period trend one.The lasting time of the anomalies after earthquake is relative to the age of groundwater.

Abstract:The Weiner filtering method is improved for removing interference factors in observation data of groundw ater dynamic of deep well in oil field. Observation data of Dongshui-3 well in Sheng li oil field are dealt with by using the improved method. The result shows that influence of the interferences on the data of groundw ater dynamic of the well can be better removed.

Abstract:The progress in the research of late Cenozoic structure and Quaternary geology of Qinghai Xizang plateau in recent years by Chinese and foreign scientists are summarized, such as the geological structure,the evolution of the plateau,the neotectonic deformation features and mechanism, as well as effect of the plateau uplifting on the environment and climate.Thinking about some problems in the research of active structure,three research areas in the future are suggested and emphasized:(1) More accurate study on the structural style,range and rate of the plateau deformation in late Cenozoic; (2) Using Quaternary geological new theory and results to the study of active structure; (3) Combining deep and shallow structure research together.

Abstract:Some kinds of anisotropy elastic constitutive relations of the crust media are discussed and a strain energy transformed equation and a calculation formula of the elastic constants of EDA cracks in a non symmetry plane are also derived.Eigenvalue equations of different anisotropy symmetry systems and their corresponding wave angular dispersion equations are discussed by introducing and deriving equations after previous authors or by the present authors. Finally, some numerical examples are simulated.