ULF magnetic emissions connected with under sea bottom earthquakes
ULF magnetic emissions connected with under sea bottom earthquakes
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与海底地震有关的超低频磁辐射
DOI：
10.5194/nhess-1-23-2001
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发表时间：
2001
影响因子：
4.6
通讯作者：
M. Hayakawa
中科院分区：
文献类型：
--
作者：
V. Ismaguilov;Y. Kopytenko;K. Hattori;P. M. Voronov;O. Molchanov;M. Hayakawa
抽象的。在地震活跃期（2000年2月1日至2000年7月26日）之前和期间，在日本进行了超低频电磁干扰测量。一个网络由两组相距140公里的磁站组成。每组由三个三分量高灵敏度磁站组成，呈三角形排列，间隔4-7公里。本文给出了在F = 0.002- 0.5Hz频率范围内与近震有关的超低频磁场变化分析结果。传统的Z/G比（Z为垂直分量，G为总水平分量）、磁梯度矢量和沿地球表面沿着传播的ULF波的相速度是在几个频段上构造的。结果表明，在F_1 = 0.1 ± 0.005，F_2 = 0.01 ± 0.005，F_3 = 0.005 ± 0.003Hz三个频率范围内，R（F）= Z/G参数的变化具有不同的特征。R（F_3）/R（F_1）比值在强震前1-3天急剧增大。在夜间（00：00-06：00 LT）的F2 = 0.01 ± 0.005 Hz频率范围内，Z、G分量的振幅和Z/G比值在地震活动期前1.5个月开始增加。地震活动开始后，高频范围的ULF发射急剧增加。磁梯度矢量（B = 1 - 5 pT/km），使用水平分量数据确定在F = 0.05 ± 0.005Hz频率范围内，各组地磁台的G值（0.03 - 0.06nT）在地震活跃期前开始指向未来的地震活动中心;而且随着地震活动中心的空间位移，使用水平分量数据确定的相速度矢量（F = 0.0067 Hz时V = 20 km/s）来自地震活动中心。垂直分量的梯度矢量指向最近的海岸（称为“海海岸”效应）。在每组地磁台上构造两个梯度向量，对地震活动中心进行定位，在本实验中给出了± 10 km的误差。
Abstract. Measurements of ULF electromagnetic disturbances were carried out in Japan before and during a seismic active period (1 February 2000 to 26 July 2000). A network consists of two groups of magnetic stations spaced apart at a distance of ≈140 km. Every group consists of three, 3-component high sensitive magnetic stations arranged in a triangle and spaced apart at a distance of 4–7 km. The results of the ULF magnetic field variation analysis in a frequency range of F = 0.002–0.5 Hz in connection with nearby earth-quakes are presented. Traditional Z/G ratios (Z is the vertical component, G is the total horizontal component), magnetic gradient vectors and phase velocities of ULF waves propagating along the Earth’s surface were constructed in several frequency bands. It was shown that variations of the R(F) = Z/G parameter have a different character in three frequency ranges: F1 = 0.1 ± 0.005, F2 = 0.01 ± 0.005 and F3 = 0.005 ± 0.003 Hz. Ratio R(F3)/R(F1) sharply increases 1–3 days before strong seismic shocks. Defined in a frequency range of F2 = 0.01 ± 0.005 Hz during nighttime intervals (00:00–06:00 LT), the amplitudes of Z and G component variations and the Z/G ratio started to increase ≈ 1.5 months before the period of the seismic activity. The ULF emissions of higher frequency ranges sharply increased just after the seismic activity start. The magnetic gradient vectors (∇ B ≈ 1 – 5 pT/km), determined using horizontal component data (G ≈ 0.03 – 0.06 nT) of the magnetic stations of every group in the frequency range F = 0.05 ± 0.005 Hz, started to point to the future center of the seismic activity just before the seismoactive period; furthermore they continued following space displacements of the seismic activity center. The phase velocity vectors (V ≈ 20 km/s for F = 0.0067 Hz), determined using horizontal component data, were directed from the seismic activity center. Gradient vectors of the vertical component pointed to the closest seashore (known as the "sea shore" effect). The location of the seismic activity centers by two gradient vectors, constructed at every group of magnetic stations, gives an ≈ 10 km error in this experiment.