断层失稳前的扩展及电阻率前兆

本文根据断裂力学,研究了体应变e的特征,导出了传播范围的近似公式;探讨了与应变有关的地震前兆的一般规律,以唐山地震电阻率前兆为实例检验了上述结果,并由电阻率前兆初步反演了相应的震源过程及某些震源参数。     

RESISTIVITY PRECURSORS AND SPREADING OF FAULT PRIOR TO ITS INSTABILITY

Based on fracture mechanics it has been found that earthquake precursors related to volumetric strain e are characterized by quadrants, blind zone and uneven propagation, and the approximate formulae for spreading range of precursor have been obtained. These results are coincident with the information of resistivity ρ_x observed before the Tangshan earthquake, and then mechanical explanations have been made for some precursors of ρ_x, such as precursors appearing concentratedly within the period of 1—2 years before the instability of the fault (i.e. subcritical period in which the fault spreads acceleratingly). Before instability of the spreading of fault, the range of e=10~(-6) reaches about 150 km, its propagating velocity is about 100 km/yr, the amplification coefficient of ρ_x is about 10~4, etc. The half length of fault before instability is about 35km. It seems that in propagating process the spreading of the fault is delayed by barrier.     

傅里叶变换轮廓术中滤波窗方位选择研究

在傅里叶变换轮廓术频域滤波过程中通常采用不对称的汉宁窗滤波窗来提取基频信号,当投影呈二维变化的光栅条纹时,采用的滤波窗长短轴方向和载频方向不吻合,会导致被测物体的部分高频信息丢失,从而影响相位展开的难易程度和系统测量的精度。分析比较物体高度的分布与频谱的关系,通过旋转滤波窗使其短轴方向与载频方向一致,可以保留物体的高频信息,降低相位展开的复杂度,提高测量的精确度。计算机模拟和实物实验结果表明滤波窗旋转滤波可以避免相位展开在物体高度突变处的出错,有效地提高测量精度。     

一种求解组合预测模型权重的新方法

在现有文献研究的基础上,对组合预测模型权重的求解方法作了进一步的研究,给出了一种求解组合预测模型权重的新方法.该方法利用最优化理论当中的库恩—塔克条件,将非线性规划模型转化为线性规划模型,从而克服了现有方法在求解组合预测模型权重时不能求得解析解的不足,最后通过示例计算验证了该方法的有效性.     

地球深部流体的状态及其在震源物理中的意义

许多地震前兆的机理与地球深部流体相关.文章介绍了与此有关的地球深部流体状态的研究进展.通过间接的证据和从若于超深井钻孔探测得到的直接证据,着重介绍了深部水的数最、存在状态和性质,估计地球深部流体孔隙压力和连通性.研究表明,地球深部高温高压状态下的水处于超临界状态,超临界水具有许多特殊性质,这些特殊性质使得流体不仅成为强震前兆的传播媒介和震源破裂过程的影响因素,而且成为直接参与震源动力过程的介质.     

GEOELECTRIC RESISTIVITY ANOMALIES BEFORE EARTHQUAKES

Since geoelectric resistivity (ρ_x) measurements were started in 1967, the following phenomena have been observed before earthquakes: ⅰ) During 2-3 years before the great Tangshan earthquake, the anomaly of ρ_x propagated outwards from the epicenter with an apparent velocity of 100 km/year, and the radius of propagation reached about 150 km. (ⅱ) Before most of the earthquakes, the resistivity drops, but before a few earthquakes it may rise; all these are controlled by the stress conditions under the geoelectric station and the source mechanism of the earthquake. The relative variation of ρ_x is a magnified (up to about 1000 times) manifestation of rock strain. (ⅲ) Before an earthquake, geoelectric resistivity may exhibit both long-term and close-upon anomalies. The long-term anomaly reflects the accelerated accumulation of stress in the seismo-genotic region; its amplitude, duration and extent are logarithmically related to the earthquake magnitude. The close-upon anomaly may be a manifestation of     

地震前地电阻率的异常变化

自1967年开展地电阻率(ρ_x)观测以来,发现地震前有以下几个现象:(1)唐山震前2—3年ρ_x异常约以100公里/年的视速度从震中向外扩展,扩展半径约150公里;(2)震前ρ_x多为下降异常,也记到一些上升变化,ρ_x的升降取决于台址下介质的受力状态并与震源机制有关,其相对变化约比应变放大10~3倍;(3)震前ρ_x异常有两类:长趋势异常,它反映孕震区应力加速积累过程,其持续时间、分布范围及幅度与震级成对数关系;临震异常,它是断层预滑的一种表现;(4)断层在震时或震后滑动有时可引起ρ_x震后效应。