50-250Hz极低频范围内的地震电磁现象研究
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摘要
采用基于地形学网格划分的时域FDTD方法来研究地震期间(震前和震期)的极低频电磁现象。由于计算能力的限制,这里主要关注的频率是50-250Hz。为了精确的仿真地震电磁环境,研究过程中引入了地形学信息和天然电磁噪声(闪电)。在仿真中,通过对震区地震电磁激发,我们设置了多个不同的观测点来观测电磁波的传播并进行比较。同时,电离层异常现象也被考虑在仿真过程中。我们的仿真结果证明了在震期电磁波存在传播异常现象,这也证明了之前研究人员所观测到的数据的正确性。最后,我们总结了地震期间的电磁传播异常现象的初步规律。
Seismic electromagnetic(EM) phenomena in the extremely low frequency(ELF) range prior to or during earthquakes are studied using the geodesic finite difference time-domain(FDTD) algorithm.Different from our previous studies,in this work the interested frequency range is extended to 100-500Hz.In order to accurately simulate the earthquake EM environment,geological information and natural EM noises are introduced.By simulating seismic EM eruptions in the earthquake zone,we have observed and recorded the EM wave propagation in different stations and have compared the results.The effects of ionospheric anomalies on the observations are also discussed.Our simulation results of the ELF wave propagation have shown the propagation anomalies,and have proved the observed results by the earthquake researchers.We have summarized,finally,the general rules of seismic EM phenomena in the specific frequency range.
Seismic electromagnetic(EM) phenomena in the extremely low frequency(ELF) range prior to or during earthquakes are studied using the geodesic finite difference time-domain(FDTD) algorithm.Different from our previous studies,in this work the interested frequency range is extended to 100-500Hz.In order to accurately simulate the earthquake EM environment,geological information and natural EM noises are introduced.By simulating seismic EM eruptions in the earthquake zone,we have observed and recorded the EM wave propagation in different stations and have compared the results.The effects of ionospheric anomalies on the observations are also discussed.Our simulation results of the ELF wave propagation have shown the propagation anomalies,and have proved the observed results by the earthquake researchers.We have summarized,finally,the general rules of seismic EM phenomena in the specific frequency range.
引文
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[11]夏汉刚,王毅,曹群生.ELF/SLF电磁波传播的FDTD和GIS结合建模与分析[J].[J].微波学报,2010,26(4):27-31
[12]Sevgi L,Akleman F,Felsen L B.Groundwavepropagation modeling:problem-matched analyticalformulations and direct numerical techniques[J].IEEE Antennas and Propagation Magazine,2002,44(1):55-75.
[13]GEODAS Grid Translator-Design-a-Grid[EB/OL].National Geophysical Data Center,NOAA,WorldData Center for Marine Geology and Geophysics,Boulder(WDC MGG),2011.
[14]Hermance J F.Electrical conductivity models of thecrust and mantle[J].Global Earth Physics:AHandbook of Physical,1995:190-205
[15]Bilitza D.International Reference Ionosphere 2000[J].Radio Science,2001,36(2):261-275.
[16]Yang H,Pasko V P.Three-dimensional finite differencetime domain modeling of the diurnal and seasonalvariations in Schumann resonance parameters[J].Radio Science,2006,42(2):1-10
[2]Ondoh T.Investigation of precursory phenomena in theionosphere,atmosphere and groundwater before largeearthquakes of M>6.5[J].Advances in Space Research,COSPAR,2009,43(2):214-223.
[3]Fraser-Smith A C,Bernardi A,McGill P R,et al.Low-Frequency Magnetic Field Measurements near theEpicenter of the Ms 7.1 Loma Prieta Earthquake[J].Geophysical Research Letters,1990,17(9):1465-1468
[4]Molchanov O.Precursory effects in the subionosphericVLF signals for the Kobe earthquake[J].Physics of TheEarth and Planetary Interiors,1998,105(3-4):239-248
[5]Ohta K,Izutsu J,Hayakawa M.Anomalous excitation ofSchumann resonances and additional anomalousresonances before the 2004 Mid-Niigata prefectureearthquake and the 2007 Noto Hantou Earthquake[J].Physics and Chemistry of the Earth,Elsevier Ltd,2009,34(6-7):441-448.
[6]Pulinets S.Ionospheric precursors of earthquakes;recentadvances in theory and practical applications[J].Terrestrial Atmospheric and Oceanic Sciences,2004,15(3):413-435.
[7]Fenoglio M A,Johnston M J S,Byerlee J D.Magneticand electric fields associated with changes in high porepressure in fault zones:application to the Loma PrietaULF emissions[J].Journal of Geophysical,1995,100(B7):12,951-12,958
[8]Wang Y,Cao Q.Analysis of seismic electromagneticphenomena using the FDTD method[J].IEEETransactions on Antennas and Propagation,2011,59(11):4171-4180
[9]Simpson J J,TafloveA.ELF Radar System Proposed forLocalized D-Region Ionospheric Anomalies[J].IEEEGeoscience and Remote Sensing Letters,2006,3(4):500-503
[10]Simpson J J.Current and Future Applications of 3-DGlobal Earth-Ionosphere Models Based on the Full-Vector Maxwell’s Equations FDTD Method[J].Surveys in Geophysics,2009,30(2):105-130
[11]夏汉刚,王毅,曹群生.ELF/SLF电磁波传播的FDTD和GIS结合建模与分析[J].[J].微波学报,2010,26(4):27-31
[12]Sevgi L,Akleman F,Felsen L B.Groundwavepropagation modeling:problem-matched analyticalformulations and direct numerical techniques[J].IEEE Antennas and Propagation Magazine,2002,44(1):55-75.
[13]GEODAS Grid Translator-Design-a-Grid[EB/OL].National Geophysical Data Center,NOAA,WorldData Center for Marine Geology and Geophysics,Boulder(WDC MGG),2011.
[14]Hermance J F.Electrical conductivity models of thecrust and mantle[J].Global Earth Physics:AHandbook of Physical,1995:190-205
[15]Bilitza D.International Reference Ionosphere 2000[J].Radio Science,2001,36(2):261-275.
[16]Yang H,Pasko V P.Three-dimensional finite differencetime domain modeling of the diurnal and seasonalvariations in Schumann resonance parameters[J].Radio Science,2006,42(2):1-10
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