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arXiv 0811.1177physics.geo-ph
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大地震高频地震P波包络的随机自相似性揭示了地震破裂的分形特征

Stochastic self-similarity of envelopes of high-frequency teleseismic P-waves from large earthquakes suggests fractal pattern for earthquake rupture

A. A. Gusev

摘要:

大地震的高频地震辐射可近似地用在近距离上记录的P波列来表示。观察到的这些信号的包络看起来随机和间歇性的,这表明非平凡的随机结构。变差函数和谱分析应用于瞬时功率计算从带滤波观测P波信号从8个大的(Mw=7.6-9.2)地震,与8-30记录每个事件和8个非重叠的频带分析(总频率范围0.6-6.2 Hz,带宽0.7 Hz)。变异函数和功率谱的估计在对数-对数尺度上看起来都是线性的,这表明在大多数情况下信号具有自相似的相关结构。赫斯特指数H的单个事件值的范围是0.71-0.80(平均波段和台站)时,估计从变异函数,和0.78-0.83时,估计从光谱。没有系统的依赖站或频带被注意到。H值在0.8左右可能是一般大地震的特征。结果表明,地震破裂过程的时空组织具有明显的分形特征。同时,为面向应用的地震强震模拟建立了一个有用的约束条件。

英文摘要:

High-frequency (HF) seismic radiation of large earthquakes is approximately represented by P wave trains recorded at teleseismic distances. Observed envelopes of such signals look random and intermittent, suggesting non-trivial stochastic structure. Variogram and spectral analyses were applied to instant power calculated from band-filtered observed P-wave signals from eight large (Mw=7.6-9.2) earthquakes, with 8-30 records per event and eight non-overvlapping frequency bands analyzed (total frequency range 0.6-6.2 Hz, bandwidth 0.7 Hz). Estimates for both variograms and power spectra look linear in log-log scale, suggesting in most cases self-similar correlation structure of the signal. The range for the individual-event values of the Hurst exponent H is 0.71-0.80 (averaged over bands and stations) when estimated from variograms, and 0.78-0.83 when estimated from spectra. No systematic dependence on station or frequency band was noticed. The values of H around 0.8 may be characteristic for large earthquakes in general. The result suggests that the space-time organization of earthquake rupture process has significant fractal features. Also, a useful constraint is established for application-oriented earthquake strong motion modeling.

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