Subionospheric VLF signal perturbations possibly related to earthquakes

A likely VLF subionospheric signal effect related to seismic activity was first reported by Hayakawa et al. [1996a, b] in association with the great Kobe earthquake. We have analyzed similar data during periods around 10 other great earthquakes (magnitude M>6) in order to understand the main features of such an effect. The following characteristics emerged from our analysis: The effect appears as a transient oscillation with a 5- to 10-day period, which is initiated a few days before a large earthquake and decays over a few days to weeks after it. It is mainly related to crustal earthquakes. It appears when resonant atmospheric oscillations with periods in a range of 5–11 days exist before the earthquake. The seismic influence on the VLF signal is probably explained by the generation of long-period gravity waves during the earthquake process and their intensification at heights of 70–90 km.

[1]  R. K. Tiwari,et al.  Strange Attractor in Nonlinear Fluctuations of Length Of the Day (LOD) Time Series , 2013 .

[2]  P. R. Julian,et al.  Observations of the 40-50-day tropical oscillation - a review , 1994 .

[3]  W. Harth,et al.  The day-to-day variation of atmospherics activity over the South American continent , 1982 .

[4]  早川 正士,et al.  Electromagnetic phenomena related to earthquake prediction , 1994 .

[5]  J. Ahlquist.  Normal-Mode Global Rossby Waves: Theory and Observations , 1982 .

[6]  Yi-Bo Luo,et al.  Long period oscillations in the equatorial ionization anomaly correlated with the neutral wind in the mesosphere , 1993 .

[7]  W. Skinner,et al.  Observations of the 5-day wave in the mesosphere and lower thermosphere , 1994 .

[8]  H. J. Hagger,et al.  Electromagnetic Waves in Stratified Media , 1996 .

[9]  M. Ladd,et al.  Low‐frequency magnetic field measurements near the epicenter of the Ms 7.1 Loma Prieta Earthquake , 1990 .

[10]  P. R. Julian,et al.  Detection of a 40–50 Day Oscillation in the Zonal Wind in the Tropical Pacific , 1971 .

[11]  J. Holton.  An introduction to dynamic meteorology , 2004 .

[12]  R. A. Madden,et al.  Further Evidence of Global-Scale 5-Day Pressure Waves , 1972 .

[13]  Umran S. Inan,et al.  VLF and LF signatures of mesospheric/lower ionospheric response to lightning discharges , 1996 .

[14]  D. Ortland,et al.  Observations of the quasi 2‐day wave from the High Resolution Doppler Imager on Uars , 1993 .

[15]  Michael Selwyn Longuet-Higgins,et al.  The eigenfunctions of Laplace's tidal equation over a sphere , 1968, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[16]  M. Salby.  Rossby Normal Modes in Nonuniform Background Configurations. Part I: Simple Fields , 1981 .

[17]  E. Kawai,et al.  Anomalies in the Sub-ionospheric VLF Signals for the 1995 Hyogo-ken Nanbu Earthquake. , 1996 .

[18]  Masashi Hayakawa,et al.  Precursory effects in the subionospheric VLF signals for the Kobe earthquake , 1998 .

[19]  D. E. Venne.  Normal-Mode Rossby Waves Observed in the Wavenumber 1–5 Geopotential Fields of the Stratosphere and Troposphere , 1989 .

[20]  A. Kasahara.  Effect of Zonal Flows on the Free Oscillations of a Barotropic Atmosphere , 1980 .

[21]  M. Hayakawa,et al.  On the precursory signature of Kobe earthquake on VLF subionospheric signals , 1997, 1997 Proceedings of International Symposium on Electromagnetic Compatibility.

[22]  R. Dickinson,et al.  The Five-Day Wave on a Sphere with Realistic Zonal Winds. , 1976 .

[23]  Yu. A. Kopytenko,et al.  Results of ULF magnetic field measurements near the epicenters of the Spitak (Ms = 6.9) and Loma Prieta (Ms = 7.1) earthquakes: Comparative analysis , 1992 .

[24]  Kiyohumi Yumoto,et al.  Results of ultra-low-frequency magnetic field measurements during the Guam Earthquake of 8 August 1993 , 1996 .

[25]  B. Morena,et al.  Quasi-periodic fluctuations in ionospheric absorption in relation to planetary activity in the stratosphere , 1991 .

[26]  M. S. Lazaridou,et al.  Latest aspects of earthquake prediction in Greece based on seismic electric signals, II☆ , 1993 .