Abstract:Based on the paper[5], this paper takes the 2-D model of three layered medium, in which the second layer and the third layer are convex, and discusses the application of boundary element method for calculating apparent resistivity. The proper, basic solution is selected, so that the integral calculation along the horizontal parts in the integral equations are avoided, and the normal derivatives of electric potential on boundaries are managed to be eliminated in the theory. So the number of all needed boundary cut joints and unknowns are much less, algebraic equation sets are on a smaller scale, computer memory and time are saved a lot. This study supplies some convenient conditions for furtherly solving the 2-D and 3-D problems of multi-layered medium (e, g. more then three layered model) which contains inhomogeneities.

Abstract:In this paper, dynamic propagations of some typical combined cracks in the physics of earthquake focus are studied by means of dynamic photoelasticity. Dynamic isochromatic fringes of these crack propagations under uniaxial compression are first successfully recorded, and the crack paths are also obtained. Experimental results show that K_Ⅱd=0 at a running crack tip even in a compres-sion-shear stress field. Mode I dynamic stress intensity factors of running crack tips are deter-mined, and a conclusion of crack stable propagation in a compression-shear stress field is ob-tained.

Abstract:In this paper, the authors have studied the seismic features in the southeast Gansu Province using the mathematic threshold autoregressive model and pisewise polynomial. The results are as follow:
1) The seismicity is of a "periodic phenomenon". There have been 3 cycles since this century. At present, the seismicity is in the third active "period".
2) Since. 1900. the seismicity has been in lower level, most of earthquakes are ones with magnitude of 5-6. The next earthquake will be one with magnitude of about 5 according to the threshold autoregressive model, and its occurring probability at present is 0.74 based on the pise-wise polynomial.
3) The pattern of space distribution of earthquakes (M>4.7) is in accordance with analog-to-digital experiment.

Abstract:This paper simply introduces the method of directly calculating the crowding index α and crowding index spectrum f(α) which can describe the complex fractal. Using f(α)-α it also analyses the seismic temporal sequence data in Tangshan seismic region. The results show that using the index spectrum f(α) to study the multi-fractal is simple and available, and uneven fractal as the temporal distribution of earthquakes can be described better and completely. Based on the anomalous shape of the index spectrum f(α), it is possible to monitor and predict large earthquakes.

Abstract:In this paper, the problems about direct identification of precursor with the tilt vector are discussed, and the method is also put forward. On the basis of tilt modulus, the max-modulus of vector is researched. The stability of tilt vector and relationship between vector characters, (for exam pie:pause, knot. radical change) are studied. The relationships between the stability of vector characters and precursors of Gonghe. Qinghai and Jingtai, Gansu and Datong, Shanxi earthquakes are discussed. The results show that the knots and pauses may be steady, therefore they are uncertainly precursor marks; however, the radical change of vector is possible precursor. The research for stability is more meaningful and effective, for precursor analysis than direct method.

Abstract:On Oct. 20. 1990, there occurred a earthquake with magnitude of 6.2 in Jingtai area, Gansu. which is main-aftershock type. The seismic active feature shows:before strong earthquake, the distribution pattern of moderate and small events changed, the seismic belt appeared impending main shock:the time fractal dimension value decreased and got the minimum, the position style of equo-distance distribution of earthquakes with magnitude of 6 occurred nearby was characterized by filling location obviously. Also. this paper suggested a new method to rapidly obtain the trend of seismic rupture and nodal face from the position of stations, relative to epicentre, with the maximum values of magnitude determined.

Abstract:In this paper, the scientific thought, the course and the measures of applying remote sensing in earthquake prediction have been proposed and treated in the theory.

Abstract:By preliminary statistics, it is discovered that the proportion of high level earthquake number to lower level event number in the world and in China is 1/8 to 1/9, that is. the latter is about 10 times greater than the former. Then the index predicting the higher magnitude earthquakes by using the lower magnitude earthquakes is studied.

Abstract:In this paper, a new processing method of phase lag of response of water level to barometric pressure is given. The formulae for calculating the barometric coefficient and lag time of the well level in consideration of lag influence are given. Taking well Lu-03 as an example, by using the new method, it is obtained that the barometric coefficient is 6.41 mm/hPa and the lag time of the response of well level to barometric pressure is 1.52h. The standard deviation of the water level corrected by barometric pressure decreases obviously.

Abstract:In this paper, a new method, which considers random occurrence and time-space nonuniformi-ty of earthquakes, and different intensity declining shapes, is used to estimate the seismic intensity that Chengdu City will suffer in coming 50 years. First, the potential sources with different upper magnitudes are zoned by combining the pattern-recognition with subjective judgement according to the features of seismology, geophysics and seismicity. Second, the b value, and seismic frequency in potential zones, and nonuniform parameters of earthquake distribution are determined by seismicity analysis in history. Third. the equivalent round, ellipse, long ellipse and fault-rupture intensity declining models which are available in western Sichuan are set up in consideration of earthquake tectonics and isoseismal shapes. At last, a simplified method for calculating probability, which considers earthquake time-space nonuniformity, is suggested to estimate the possibility of intensity from Ⅳ to Ⅸ. The assessment will provide scientific basis for earthquake resistant project in the City.

Abstract:In this paper, based on the analysing of horizontal remnant stress-strain fields near the Red River fault, the calculation of 2-D finite element method with six different tectonic stress directions, and other related data, the current stress field and the seismic danger areas are inferred. The results indicate that the current stress field in this area is very complex and shows regionalized features, but the dominant direction of principal compressive stress is nearly NS. The Yongsheng area. Jianchuan-Eryuan area, and the area surrounded by Dali. Xiaguan and Binchuan are coming seismic danger areas. When the principal compressive stress axis rotates toward northwest, the Yongping, Puer-Simo, Eshan, Shiping, and Tonghai are as will become seismic danger areas.

Abstract:地震前后地下水气体逸出异常的现象已引起人们的关注,国内外学者开展了多方面的观测,积累了丰富的资料。

Abstract:为了适应地电阻率法预报地震的需要,许多学者已在地电阻率理论计算方面进行了深入研究。文献[1]给出了水平层状介质视电阻率的不同计算方法,并对各种方法的计算精度作了评价;文献[2]则对地电阻率随时间的变化作了数值模拟。

Abstract:台湾东北部现代地壳运动强烈,地震活动水平很高。1986年3月22-28日在钓鱼岛西南海域发生一次中强震群活动,同年11月15日在花莲附近海中发生了7.6级大震,泉州地震台观测到了一些值得注意的震相特征。

Abstract:地震资料取自新疆地震目录^[1],对其中个别的地震进行了重新分析处理。

Abstract:根据已有的地震活动资料可以看出,地震的发生在空间上极不均匀,在时间上也极不平稳,并且其过程随时间的发展也不是简单的周期性变化。因此地震的孕育和发生是随机性很强的复杂过程,用一般较简单的函数来拟合这种过程不可能得到很好效果。

Abstract:In the past two decades, field observation, laboratory experiments, and the theoretical studies in the study on earthquake prediction have been carried out in several countries, by using ρ_s method, and valuable results have been achieved^{[1]-[11]-[19]-[23]}.