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从分形几何的新视角出发,分析近断层地震动的不规则性和复杂性.利用盒维数法计算了来自台湾集集地震和美国北岭地震的30条近断层地震动加速度时程的分形维数.计算结果表明,这些地震动加速度时程具有统计分形特征.近断层地震动运动特征对其分维数影响明显,滑冲效应脉冲地震动的分维数平均值最小,向前方向性效应脉冲地震动的分维数平均值居中,无脉冲地震动的分维数平均值最大,其波形不规则程度也最高.而且,地震动时程的分维数反映了其频谱特性,可作为频谱周期的表征参数.地震动的分维数D与特征周期Tc具有较强的负相关关系.最后,对于近断层地震动作用下单自由度(SDOF)体系的弹性和非弹性动力反应时程,应用盒维数法计算了其分形维数,考察了其分形性质. 相似文献
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运用分形理论的基本原理,选取了河北京津7口井的水氡观测资料,进行了广义分维计算。从所计算的7口井1972-1978年广义分维动态曲线上可见,1976年7月唐山7.8级地震前,有5个井孔资料降维过程明显,2个井孔资料的降维过程不太明显,有2个井孔资料的广州分维值在 震后仍下降,分维值大小也因不同井孔而异。结果表明:震前降维可为地震预报提供依据。 相似文献
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本文就地震预报中常用的分形几何中的几个数学概念做了简要的介绍,包括测度,豪斯道夫维数、计盒维数等,并介绍了有关维数的性质和估计方法。作者试图通过了这些数学概念的简要介绍,使读者对分维有更准确的理解。 相似文献
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利用模糊集理论和分形理论结合的模糊分维方法,处理了山东聊古-1井水氡10多年来的观测资料,找出了水氡模糊分维值的3次较大变化与相应3次地震的关系。在这3次地城丧水氡模糊分维值都出现明显地小于0.57的低值异常变化。这可能反映了系统在较大地震前的明显降维特征。 相似文献
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地震时空分布结构的多重分形特征的研究 总被引:4,自引:0,他引:4
地震作为地壳内的大尺度破裂被认为是分形的,具有分数维的特征。根据多重分形的观点,本文研究了部分曾发生过中强以上地震地区小震时空分布特征,应用固定质量法计算了地震时空分布的广义分维Dq,并得到了分形奇异谱f(α)-α。初步分析结果表明:地震空间分布具有非均匀的分形结构,D∞的分维值比D0和负q的Dq值稳定。D∞的时间变化实例表明:D∞在大震发生前降低。这意味着地壳应力场非均匀程序的变化,进而简略地讨 相似文献
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采用关联维方法对台湾地区地震活动的空间特征进行了研究。先利用 10 0a来台湾的地震目录计算各个地震区、带的关联维数 ,将地震空间分布的分形特征定量表达出来 ,然后综合分析地震空间分布的关联维数和孕震构造环境之间的关系 ,得出了以下结论 :1)台湾东、西部地震区由于地震属于不同的大地构造单元 ,因此关联维数有较大的差异 ;2 )在各地震区内部的各个地震带由于板块构造、地壳结构、活断层分布上的差异 ,而具有与其构造特征相对应的关联维数 ;3)各地震带内部的各个不同的部位又由于不同的构造应力场 ,而导致地震分布上出现不同的丛集性 ,表现为不同的关联维数。这些结论充分说明通过关联维分析所得到的地震活动的空间图像与地震活动所代表的不同地质构造背景有着良好的对应关系 相似文献
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Monte Carlo Studies of Relations between Fractal Dimensions in Monofractal Data Sets 总被引:1,自引:0,他引:1
—Within the fractal approach to studying the distribution of seismic event locations, different fractal dimension definitions and estimation algorithms are in use. Although one expects that for the same data set, values of different dimensions will be different, it is usually anticipated that the direction of fractal dimension changes among different data sets will be the same for every fractal dimension.¶Mutual relations between the three most popular fractal dimensions, namely the capacity, cluster and correlation dimensions, have been investigated in the present work. The studies were performed on the Monte Carlo generated data sets. The analysis has shown that dependence of the fractal dimensions on epicenter distribution, and relations among the fractal dimensions, are complex and variable. Neither values nor even inequalities among dimension estimates are preserved when different fractal dimensions are used. The correlation and the capacity dimensions seem to be good tools to trace collinear tendencies of eipicenters while the cluster dimension is more appropriate to studying uniform clustering of points. 相似文献
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震级—频度关系的非线性特征 总被引:1,自引:0,他引:1
在假设地震断裂系统具有分形特征前提下,推导出非线性震级-频度关系公式:LogN=a+b△M-C/△M,作为示例,用此公式对一些实际观测资料进行了最小二乘拟合,效果明显好于线性公式。 相似文献
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We examined the behavior of different fractal dimensions when applied to study features of earthquake spatial distribution
on different types of data. We first examined simulated spatial fields of points of different clustering level, following
the so called Soneira-Peebles model. The model was chosen because it displays some similarity to the real clustering structure
of earthquakes occurring on hierarchically ordered faults. The analysis of the capacity, clustering and correlation dimensions
revealed that their behavior did not completely correlate with the clustering level of the simulated data sets. We also studied
temporal variations of the fractal coefficients, characterizing the spatial distribution of the 1999 İzmit-Düzce aftershock
sequence. The calculated coefficient values demonstrated analogous behavior like for the simulated data. They exposed different
variability in time, but for all of them a systematic fluctuation was observed before the occurrence of the Düzce earthquake.
Our analysis revealed that although fractal coefficients could be applied to measure earthquake clustering, they should be
used with caution, trying to figure out the best coefficient for a certain data set. 相似文献
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Shi Xingjue Xu Heming Niu Zhiren Fan ZengjieUniversity of Science Technology of China Hefei China Seismologicai Bureau of Shanxi Xi'an China 《中国地震研究》1994,(3)
The measured profiles of laboratory fractured rocks should be self-affine fractal.The scaling properties of these profiles are described by two parameters-the fractal dimension D and the crossover length tc The D values of eight profiles are calculated by the ruler method and by the standard deviation method respectively.It is shown that if tc is far greater than the sampling step tc two methods yield the same results,although if it is far smaller than r,the D by the standard method will be about 1.20,while D by the ruler method will very close to 1.0,because two fractal dimensions,local and global,exist on two sides of tc In order to obtain the local fractal dimension which may be close to that of the standard deviation method,the ruler method must be modified.We propose a way to estimate the tc and to modify the ruler method.Finally,a profile having given D is generated in terms of the principle of non-integer order differential,through which the above two methods are verified and lead to the same res 相似文献
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分形方法在地震序列类型早期判别中的应用 总被引:3,自引:0,他引:3
着重讨论了地震序列的空间分布随时间变化的特性,利用分形方法提取大震后余震的空间分维信息,从而达到早期判别地震序列类型的目的。以1966年以来定位精度较好、余震记录较全的12个7级以上大震和大同6级强震序列为资料,计算了震后1个月内余震随时间变化的空间分维数。结果发现,不同类型的地震序列分维数不同。一般震后5-6天,主震型序列的分维数在1.1-1.2之间,多震型序列的分维数在1.3以上。利用前7天的 相似文献