Scaling characteristics of ULF geomagnetic fields at the Guam seismoactive area and their dynamics in relation to the earthquake
Scaling characteristics of ULF geomagnetic fields at the Guam seismoactive area and their dynamics in relation to the earthquake
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关岛地震活动区超低频地磁场尺度特征及其与地震的动态关系
DOI：
10.5194/nhess-1-119-2001
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发表时间：
2001
影响因子：
4.6
通讯作者：
D. Volobuev
中科院分区：
文献类型：
--
作者：
N. Smirnova;M. Hayakawa;K. Gotoh;D. Volobuev
本文研究了关岛地震活动区超低频地磁场标度（分形）特征的长期演化与1993年8月8日附近强震（Ms = 8.0）的关系。所选时间段为震前10个月和震后10个月。本文用FFT方法、Burlaga-Klein方法和Higuchi方法计算了超低频时间序列的标度指数和分形维数。它被发现的光谱的ULF排放表现出，平均而言，幂律行为S（f）/ f，这是一个典型的分形（自仿射）时间序列的指纹。的频谱斜率波动准周期性的过程中的时间在= 2.5 - 0.7的范围内，这对应于分数布朗运动的持久性和反持久性的行为。随着地震日期的临近，谱斜率有逐渐减小的趋势。这种趋势在所有的局部时间都表现出来，表明在大地震事件附近，超低频噪声的结构逐渐演变为典型的闪烁噪声结构。我们建议将这种特殊性视为地震前兆特征。还揭示了与地震有关的另一个效应：地震期间ULF发射谱斜率变化的最长准周期（27天）消失，地震后3个月又出现。在SOC（自组织临界性）概念的基础上对所揭示的特性进行了物理解释。
The long-term evolution of scaling (fractal) char- acteristics of the ULF geomagnetic fields in the seismoactive region of the Guam Island is studied in relation to the strong (Ms = 8.0) nearby earthquake of 8 August 1993. The se- lected period covers 10 months before and 10 months after the earthquake. The FFT procedure, Burlaga-Klein approach and Higuchi method, have been applied to calculate the scal- ing exponents and fractal dimensions of the ULF time se- ries. It is found that the spectrum of ULF emissions exhibits, on average, a power law behaviour S(f) / f , which is a fingerprint of the typical fractal (self-affine) time series. The spectrum slope fluctuates quasi-periodically during the course of time in a range of = 2.5 0.7, which corresponds to the fractional Brownian motion with both persistent and antipersistent behaviour. An tendency is also found for the spectrum slope to decrease gradually when approaching the earthquake date. Such a tendency manifests itself at all lo- cal times, showing a gradual evolution of the structure of the ULF noise to a typical flicker noise structure in proximity to the large earthquake event. We suggest considering such a peculiarity as an earthquake precursory signature. One more effect related to the earthquake is revealed: the longest quasi- period, which is 27 days, disappeared from the variations of the ULF emission spectrum slope during the earthquake, and it reappeared three months after the event. Physical interpre- tation of the peculiarities revealed has been done on the basis of the SOC (self-organized criticality) concept.