Abstract:The problems about the sequence features,causative structures and prediction of the swarms near Mt. Niushoushan of Ningxia in 1995 are discussed in this paper.It is considered that these swarms were all premonitory events,which did not relate to the water storage of the Qingtongxia reservoir and resulted from the action of a few fractures in different directions.

Abstract:On the basis of analysis about the tectonic systems of the North-South seismic belt,the evolution of time-space dynamic pattern of seismicity is studied. The results show that the seismicity has the characteres as follow:① migration along the latitude direction,there are two kinds of migratory states in space,i.e. stepforward style and stepforward-return style;② the rapid respond in far distance;③ chain distribution of induced earthquakes,this feature indicates the coupling between strong quakes,and supports the trace for the position of future strong events;④ common repeat basis quality in space and time.The conclusions have certain practice values for judging the trend and realizing the correct prediction.

Abstract:In this paper, the relationship between seismicity in the Northwest China and three components of the Lunar and Solar tide-generating force has been researched deeply.Based on the geological structure in the region, authors let one of two horizontal components of the tidal force parallel to rupture strike and another perpendicular to that.The result shows that there is an important relationship between seismicity and two horizontal components simultaneously,and parallel one is more important than vertical one.This result has more important significance for predicting occurrence time of an earthquake.

Abstract:Anomaly characteristics of earth-resistivity,hydrochemistry,underground water behaviors,ground stress and deformation during the Yongdeng M_S5.8 earthquake in Gansu Province on Jul. 22, 1995 were studied, and so the following conclusions were obtained:① The spatial distribution of medium-short (one year time scale) and short-imminent anomalies accords with the special relation of ‘anomaly-focal site-causitive mechanism active-master fault’ put forth by authors, and the medium period anomaly which lasted about 2-3 years is concentratedly distributed along the NW fault zone on north margin of west Qinling mountain and Haiyuan-Tongwei-Wudu fault zone. ② The additional compression stress field in the NNW-SSE direction come into being during one year before the earthquake, which caused the displacement of the focal fault. ③ The focal precursors are concentratedly distributed around the focal area, while the field precursors occur along the two active master faults mentioned above. Most of anomalies belong to the focal precursors, while a few anomalies are the field precursors. As far as duration time of anomalies,the field precursors appeared more precedently than the focal precursors.

Abstract:Based on the detailed analysis of M-t diagram,frequency diagram and epicenter distribution diagram and the statistical analysis of correlative earthquakes,it is suggested that the M_S≥5 events in the Mt. Qilian seismic zone are characterized by evident periodicity,migration from east to west and correlativity with the seismicity in west segment of Mt. Tanggula and Lancang Menglian region.

Abstract:A kind of mechanical source pattern of upwelling mantle material in the process of earthquake preparation is simulated by taking a dilatancy cone cylinder bodyin two-layer medium as a model.The variations of stress and strain as well as displacement in the medium are calculated when the analogous mechanical source of the cone cylinder body changes in different lateral and lengthwise scales as well as taper angle under the condition of layered medium.The results show that the fields of stress and strain as well as displacement in the medium or near the ground surface relate not only to the geometric and physical parameters of upwelling mechanical source,but also to the geometric parameters of layered medium structure.This numerical simulation provides a significant method for explaining why the upper mantle material flows into lower crust and show that the variation of medium structure must be considered for recognizing the distribution of precursor fields related to this kind of seismogenic process.

Abstract:According to characters of the deep and shallow tectonics in seismic area and the results of field investigation,the meizoseismal region of the Tianzhu-Gulang M_S5.4 earthquake on June 1,1996 is located at the intersection of Gulang fault and Wuwei-Tianzhu fault,the intersection is easy to accumulate and release stress. This earthquake results from the joint action of the active faults.

Abstract:Abnormal variation of the LURR(Load/unload response ratio) before and after the Menyuan M_S6.4 earthquake is studied. The abnormal variation of LURR before the earthquake is obvious. The temporal evolution of the LURR in the Menyuan area mirrors seismogenic process of the region.

Abstract:The distribution characteristics of the heat flow in Yunnan have been expounded,the vertical distribution of the heat production for the crust and upper mantle has been discussed from the crustal structure,and the structure of deep heat flow in Yunnan has further been studied.The studies indicate that the heat flow from the upper crust is greatest vertically, greater from the middle crust and smallest from the lower crust,and quite large differences exist laterally in the structure of deep heat flow among various tectonic units.The range of mantle heat flow is from 19 to 57 mW/m² in whole Yunnan region.

Abstract:The characteristics of the seismic precursors of hydrogeochemical elements from seismic source and tectonic field in well Liaogu-1 before the Heze M_S5.9 earthquake in 1983,etc.are discussed by analyzing the conditions of structural geology and hydrogeology of the well.Using the knowledges obtained from the theory on fracture displacement and experiment on rock mechanical characters,authors also have probed into the forming mechanism and prediction significance on the seismic precursors of the hydrogeochemical elements from seismic source and tectonic field.The results obtained from the paper enrich the knowledges of seismic precursors from seismic source and tectonic field and are of significance to earthauqke prediction.

Abstract:On the basis of recent study on Biot theory and quasi static hypothesis,the three basic parameters of Biot's theory,i.e.α,M and m which were unclear,are acquired manifestly by the way of comparison.What this paper suggests would make Biot theory convenient to use.

Abstract:Popularization and application of the new method for demarcating radonscopes by using solid radon gas source have made encouraging progress and marked effect. The method solved many problems existing in demarcating radonscopes fora long time. Its practical application took positive effect on speeding up the realization of standardizaton management of the national seismic hydrochemical metwork demarcation techniques and showed notable social and economic benefits.

Abstract:Analyses and comparison of the water quality of each monitoring station with national water quality standards were carried out based on the accumulated data formany years from earthquake monitoring net of ground fluid in Gansu Province.Dynamic analysis of some items was involved.The results show that water quality of springs in the region has been comparatively steady for more than 20 years.Water quality of most of springs,except a few,exceeds the national drinking water quality standards.However,this depends on the water source itself rather than pollution from surrounding environment.

Abstract:According to the reasonable test materials,the authors have studied the active fracture structure framework in Huangshui basin,made the laser scattering simulation test,obtained the quantitative explicit results of the active fracture characteristics and used the results to evaluate regional crust stability.

Abstract:A graphic software tool is introduced in this paper,which is used to browse and process continuous waveform data for magnetic recording.The tool has many functions,it can be used to operate on magnetic medium in many ways and to browse and to display extractive continuous waveform file in many random ways.In addition,it can be used to process the files which are displayed in many modes. The tool provides many operation modes such as menu,button,etc.,it is very convenient, flexible and useful.

Abstract:Effective distance to reduce seismic intensity on two sides of the main fault causing the 1920 Haiyuan M8.5 earthquake is about 160 km.Within the distance no M>6.5 earthquake will occur during the future several hundreds of years.Because Lanzhou City is 120 km away from the main fault, in the city no M>6.5 earthquake will occur in a few hundreds of years.Structures and buildings in Lanzhou City were designed according to antiseismic standard of Ⅷ degree on the intensity scale.Even though a M6.5 earthquake will occur in future,its destruction would not be too heavy.It is a consideration in the worst case.

Abstract:According to the theory of super nonlinear velocity,it is discovered that angular velocity of the earth rotation decreases from the inner to the outer region along the earth radius.Then based on this result,the calculated velocity of drift from the east to the west of the earth crust is 1.75 cm per year about the earth equatos surface.The value is agreed with the measured data.