地震期间的超低频电磁波传播异常研究
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摘要
主要研究了地震期间可能出现的物理现象对人工电磁信号传播产生的影响。这里采用的仿真方法是基于地形学网格划分的时域FDTD方法,主要关注的频率范围是50~250Hz(超低频)。为了精确地仿真地震期间可能出现的电磁环境,研究过程中主要考虑了震区地下动电效应电流源和电离层异常现象,同时也讨论天然电磁噪声(闪电)的影响。研究表明,在地震的特殊物理环境下,受到不同因素的影响,超低频电磁波的传播出现了不同类型的异常现象,这也证明了观测结果的正确性。最后,总结了地震期间的超低频电磁信号传播异常现象的规律,并指出了采用人工方式来监测和预测地震的可行性。
This investigation focuses on the effect of abnormal physical mechanisms on the artificial electromagnetic (EM) signal propagation during earthquakes. The geodesic FDTD method is applied to this study to simulate EM wave propagation in extremely low frequency (ELF) range of 50-250 Hz. The effects of currents caused by electrokinetic effect and ionospheric anomalies are mainly considered, as well as the background noises (the lightning). The results show the propagation anomalies during earthquakes, which also prove the observation results by former researchers. Finally, basic phenomena of EM propagation anomalies are summarized and potentials of artificial monitoring earthquakes are proposed.
This investigation focuses on the effect of abnormal physical mechanisms on the artificial electromagnetic (EM) signal propagation during earthquakes. The geodesic FDTD method is applied to this study to simulate EM wave propagation in extremely low frequency (ELF) range of 50-250 Hz. The effects of currents caused by electrokinetic effect and ionospheric anomalies are mainly considered, as well as the background noises (the lightning). The results show the propagation anomalies during earthquakes, which also prove the observation results by former researchers. Finally, basic phenomena of EM propagation anomalies are summarized and potentials of artificial monitoring earthquakes are proposed.
引文
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[12]Tao Y,Tian M,Yungang W,et al.Study of the ionospheric anomaly before the Wenchuan earth-quake[J].Chinese Science Bulletin,2009,54(4):493-499.
[13]Sentman D D,Fraser B J.Simultaneous observa-tions of Schumann resonances in California and Aus-tralia:Evidence for intensity modulation by the local height of the D region[J].Journal of Geophysical Research,1991,96(A9):973-984.
[14]Yang H,Pasko V P,Sátori G.Seasonal variations of global lightning activity extracted from Schumann resonances using a genetic algorithm method[J].Journal of Geophysical Research,2009,114(D1):1-10.
[15]王毅,苏冰柏,曹群生.50～250Hz极低频范围内的地震电磁现象研究[J].微波学报,2012,28(S2):408-411.Wang Yi,Su Bingbo,Cao Qunsheng.Study of seis-mic electromagnetic phenomena in the ELF range50-250Hz[J].Journal of Microwaves,2012,28(S2):408-411.
[16]Wang Y,Xia H,Cao Q.Analysis of ELF attenua-tion rate using the geodesic FDTD algorithm[C]//2010International Conference on Microwave and Millimeter Wave Technology.Seremban,Malysia:IEEE,2010:1413-1415.
[17]Hermance J F.Electrical conductivity models of the crust and mantle,in global earth physics[M].American Geophysical Union,Washington D C:[s.n.],1995.
[2]Ondoh T.Investigation of precursory phenomena in the ionosphere,atmosphere and groundwater before large earthquakes 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 the epicenter of the Ms7.1loma prieta earthquake[J].Geophysical Research Letters,1990,17(9):1465-1468.
[4]Molchanov O.Precursory effects in the subiono-spheric VLF signals for the Kobe earthquake[J].Physics of the Earth and Planetary Interiors,1998,105(3/4):239-248.
[5]Singh R,Veenadhari B,Cohen M B,et al.Initial results from AWESOME VLF receivers:set up in low latitude Indian regions under IHY2007/UNBSSI program[J].Current Science,2010,98(3):398-405.
[6]Ohta K,Izutsu J,Hayakawa M.Anomalous excita-tion of Schumann resonances and additional anoma-lous resonances before the2004Mid-Niigata prefec-ture earthquake and the2007Noto Hantou Earth-quake[J].Physics and Chemistry of the Earth,2009,34(6/7):441-448.
[7]Pulinets S.Ionospheric precursors of earthquakes;recent advances in theory and practical applications[J].Terrestrial Atmospheric and Oceanic Sciences,2004,15(3):413-435.
[8]Fenoglio M A,Johnston M J S,Byerlee J D.Mag-netic and electric fields associated with changes in high pore pressure in fault zones:application to the Loma Prieta ULF emissions[J].Journal of Geophys-ical,1995,100(B7):951-958.
[9]Wang Y,Cao Q.Analysis of seismic electromagnetic phenomena using the FDTD method[J].IEEE Transactions on Antennas and Propagation,2011,59(11):4171-4180.
[10]Simpson J J,Taflove A.ELF radar system proposed for localized D-region ionospheric anomalies[J].IEEE Geoscience and Remote Sensing Letters,2006,3(4):500-503.
[11]Majaeva O,Fujinawa Y,Zhitomirsky M E.Model-ing of non-stationary electrokinetic effect in a con-ductive crust[J].J Geomag Geoelectr,1997,49:1317-1326.
[12]Tao Y,Tian M,Yungang W,et al.Study of the ionospheric anomaly before the Wenchuan earth-quake[J].Chinese Science Bulletin,2009,54(4):493-499.
[13]Sentman D D,Fraser B J.Simultaneous observa-tions of Schumann resonances in California and Aus-tralia:Evidence for intensity modulation by the local height of the D region[J].Journal of Geophysical Research,1991,96(A9):973-984.
[14]Yang H,Pasko V P,Sátori G.Seasonal variations of global lightning activity extracted from Schumann resonances using a genetic algorithm method[J].Journal of Geophysical Research,2009,114(D1):1-10.
[15]王毅,苏冰柏,曹群生.50～250Hz极低频范围内的地震电磁现象研究[J].微波学报,2012,28(S2):408-411.Wang Yi,Su Bingbo,Cao Qunsheng.Study of seis-mic electromagnetic phenomena in the ELF range50-250Hz[J].Journal of Microwaves,2012,28(S2):408-411.
[16]Wang Y,Xia H,Cao Q.Analysis of ELF attenua-tion rate using the geodesic FDTD algorithm[C]//2010International Conference on Microwave and Millimeter Wave Technology.Seremban,Malysia:IEEE,2010:1413-1415.
[17]Hermance J F.Electrical conductivity models of the crust and mantle,in global earth physics[M].American Geophysical Union,Washington D C:[s.n.],1995.
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