Abstract:Based on terrain elevation isolines from topographic maps with scale 1:50 000 and 1:1 000 000 in Tianshan area in Xinjiang, the fractal dimensions of isolines in 6 studying sectors from 3 different types of geomorphology, including high mountain, low -moderate mountain and catchment basin, are computed by using successive coarsening method. The results show that all the studied isolines are statistical fractals, and the fractal dimensions take on different characters for different geomorphological regions and scale ranges. It can be inferred that the fractional dimension values are closely dependent on the erosional intensities, and it can be a very important parameter in geomorphological and geodynamic researches.

Abstract:Based on the detail derivation of seismic wave velocity in weak anisotropy medium, some calculation methods using Pn phase to upper mantle anisotropy are introduced; the inversion approaches of upper mantle anisotropy using SKS and ScS phases are illustrated and their advantages or disadvantages and relations are also analyzed.

Abstract:Based on the model from HT -HP rock experimental result and theoretical analysis, for epicenter area of strong and moderate earthquake, the properties and mechanical behaviors of rock deformation and failure under the condition of different temperature and pressure are studied. According to the model, during a loading circle, the small earthquakes move to the deeper crust gradually with the tectonic stress increases. The relocation results of some earthquake sequences support this concept model. Considering the mechanical behaviors of rock incremental failure and abrupt instability, the enhancement and quiescence phenomena of seismic activity before middle and strong earthquake, as well as the changing characteristics of b -value are studied primarily. The potential mechanism of two kinds of quiescence and change of b -value are discussed.

Abstract:The increasing rhythm of pore-water pressure and cyclic softening behavior is discussed by tests on saturated compacted loess. The results indicate that saturated compacted loess can liquefies subjected to dynamic loads, the curve of pore-water pressure of it is similar to that of initial loess, and it displays softening nature subjected to cyclic loads. In engineering, reconstituted loess, if it is saturated or almost saturated, can liquefies and deforms strongly.

Abstract:The seismic subsidence is one of major disasters in loess areas in China. The deformation mechanics of loess structure under earthquake loading are analyzed. By using electronic-microscope scanning, microstructure and grain shape of Q₃ loess, which has seismic subsidence property, are studied. It indicate that the microstructure of loess has great influence not only to the seismic subsidence coefficient, but also to the critical dynamic stress. Through the quantitative test analysis of pore content, the influence of middle-large pores on loess seismic subsidence is discussed and some items of loess samples' microstructure are compared and analyzed.

Abstract:Through quantitative tests and numerical analysis of pore contents of loess, computer-added image manipulation method of microstructure of loess pore is introduced and the mechanism of saturated loess liquefaction is studied. The quantitative relations of pore microstructure and loess liquefaction potential are established and the loess liquefaction potentials in different areas of china are estimated with pore microstructure.

Abstract:Baced on the analysis to water quality of Waguanshan spring from documents of 1972~1997, the Influence of environmental pollution in lanzhou area to the dynamic behavior of hydrogeochemistry in the spring water is studied. It shows that the environment pollution, especially air pollution,may influence the spring water greatly. So the environment pollution should be considered when use data of dynamic behavior of hydrogeochemistry in underground water to earthquake prediction.

Abstract:The Jingyang earthquake which occurred on January 5, 1998, is the greatest one in recent forty years in Shaanxi province. The tectonic background and feature of geophysical field of the earthquake are studied.

Abstract:The information of seismic wave in south Tianshan is analyzed systematically by using records of 49 years on 5 stations, extracted anomalous criterion and prediction indexes, and R evaluation are given.

Abstract:Comprehensive weighted information content of seismic precursors is a new method, in which anomaly event is comprehensive estimated by using "seismic prediction exprert system", and considering the reliability, validity, significance and dependence every anomaly is given a weighted count. The comprehensive weighted information contents of seismic precursory since 1977 in Shandong provence are calculated and the information content variation before and after the Heze M_S 5.9 earthquake on Nov. 7, 1983, is analysed.

Abstract:The focal-mechanism solutions of 372 earthquakes in Ningxia and its neighboring regions are evaluated by using Nulff net. Basing on these data the direction of principal compressive stress and principal strain stress in this region are obtained by use Wulff net again. The dominant direction of P axle is NE 30°~70°,and one of T axle is NW 300°~330°. According main acting force is horizontal or nearly horizontal,most of the tectonic faults which causing earthquake should be strike-slip or nearly strike-slip faults.

Abstract:Three cases of Xingtai M_S5.8,Heze M_S5.9 and Sheyang M_S5.1 earthquakes are chosen and the fracture feature of moderate and small shocks before the earthquakes are studied. The result shows:1. The shocks occurred during the seismogenic period show ten dency of unilateral fracture; 2. The shocks before Xingtai and Heze earthquakes possess a dominant direction of fracture plane,that is similar or conjugate to the strikes of seismic belts and fracture planes of main earthquakes; 3. The environment stress τ₀ of the shocks before the earthquakes is slightly larger than those during the normal period; 4. There is not a dominant direction of fracture plane for the shocks before Sheyang earthquake, therefore it is deduced that there is not seismic belt before the event; 5. Before Heze and Sheyang earthquakes,the moderate and small shocks occurred on the edge of seismic gaps show tendency of unilateral fracture, and their directions of principal fracture generally do not point to the interior of gaps.

Abstract:Adopting the fuzzy fractal method which combines fuzzy set theory and fractal theory, the fuzzy fractal values of dynamic water -level in yu -01 well, Fanxian county, Henan Province, are calculated, and the relationship between the fuzzy fractal value and three earthquakes (Ningjin M_S5.8 in 1981, Heze M_S5.9 in 1983, and Renxian M_S5.0 in 1985)is analysed. The result shows an abnormal characteristic that the fuzzy fractal value fell down to less than 0.75 apparently before three earthquakes, and the larger the degree of earthquake is and the smaller the epicentral distance is, the longer the time of abnormal characteristic last.

Abstract:The detectability of Shaanxi digital seismic network is given by using the brond-bank digital date of backgound noise record. The effective dynamic measurement range of net is analysed by backgound noise in the frequency range of 1.0~10 Hz.

Abstract:The distribution, structural pattern, combination model and surface feature of Nileke earthquake fault on March 8, 1812, are studied. The seismic fault is dip-slip type, consists of three segments and distributs as same as Kashi rive fault. Main seismic faults are normal fault, strike slip-normal fault, thrust fault and seismic crack. The vertical displacement is four times of horizontal one. The disagreement of the seismotectonic and the seismic fault is discussed.

Abstract:The characteristic of seismicity and recorded seismic waveform from 1987 to 2000 in Maqu region are studied. It is found that the earthquake swarms since 1988 are different from previous, and there is a anomaly background for middle-strong earthquake.

Abstract:自《西北地震学报》2001年第4期发表了笔者的文章《2001年厄尔尼诺事件的天文条件》以来^[1],全球气候异常越来越显著.近期研究发现,近地潮与日月大潮的叠加有6~8个月的准周期变化,厄尔尼诺事件发生时间与强潮汐时段有很好的对应关系.