A study of ionospheric response to regional seismic activity by VLF radio sounding

Self Cite

Abstract.A signal transmitted by Japan Time Standard LF station (40 kHz, Fukushima prefecture) and recorded in Petropavlovsk-Kamchatski (Russia) is analyzed during a time interval from 1 July 2004 till 24 January 2005. This interval is characterized by quiet seismic conditions up to the beginning of November, but rather strong seismic activity occurs in November and December not far from Hokkaido (Japan) and in the region of northern Kuril Islands. There were three series of earthquakes with M=5.6-7.1 in a zone of sensitivity of our wave path during two months. Nighttime "bay-like" phase and amplitude anomalies of the LF signal are observed several days before and during every series of earthquakes. During the whole period of seismic activity a significant shift in terminator times is also evident. The spectrum of LF seismo-induced anomalies shows a clear increase for the period of about 25 min.

“…Anomalies in phase and amplitude of VLF/LF signals before earthquakes with M>5.5 have been reported recently (Rozhnoi et al, 2004;Shvets et al, 2004).…”

Section: Introductionmentioning

confidence: 66%

Anomalies of LF signal during seismic activity in November–December 2004

Рожной

Solovieva

Molchanov

et al. 2005

Self Cite

“…Our analysis for Wenchuan EQ, which occurred at a shallow depth of 19 km, also shows similar results for amplitude fluctuation and dispersion (significant increase) but no significant change in trend. The observed VLF propagation anomalies in trend, fluctuation and dispersion have been explained in terms of acoustic and gravity wave channel, also called atmospheric gravity wave (AGW) channel by many previous researchers (Molchanov et al, 2001;Shvets et al, 2004;Hayakawa et al, 2010), which are generated near seismo-active region and travel up to the ionosphere and modify the ionospheric properties.…”

Section: Amplitude Perturbationsmentioning

confidence: 99%

“…Shvets et al, 2004;Hayakawa et al, 1996). In TT method attention is paid to the time of terminator (around the sunrise and sunset of local time) and time shifts are analyzed near the terminator time before and after the EQ (Hayakawa et Fig.…”

Section: Vlf Data and Analysismentioning

confidence: 99%

“…The NF method has been well explained by many researchers (e.g. Shvets et al, 2004;Hayakawa et al, 2010) and is suitable to study EQ effects on long propagation path (>1000 km). In this method particular attention has been given to the data during the local nighttime portion of 19:00-03:00 LT at the receiving station during which entire path (transmitter-receiver great circle path) is in dark and the mean nighttime amplitude, dispersion and nighttime fluctuation are estimated.…”

Section: Vlf Data and Analysismentioning

confidence: 99%

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Sub-ionospheric very low frequency perturbations associated with the 12 May 2008 <i>M</i> = 7.9 Wenchuan earthquake

Maurya¹,

Singh²,

Veenadhari

et al. 2013

“…VLF waves travel within the Earth-ionosphere wave guide, reflected by the lowest ionospheric region (the D-region during daytime and the E-region at night); in this sense, VLF phenomena can provide useful information on ionospheric conditions. Several studies have analysed VLF radio transmitted signals and reported perturbations of phase and amplitude in association with earthquakes (Gokhberg et al, 1989;Hayakawa and Fujinawa, 1994;Morgounov et al, 1994;Parrot, 1995;Nagao et al, 2002;Shvets et al, 2004). Another physical quantity that provides information on ionospheric long-term changes is the terminator time (TT), i.e.…”

Section: Introductionmentioning

confidence: 99%

Magnetic and Electromagnetic signals related to tectonic activity: updates and new analyses on measurements in Central Italy

Mauro

Lepidi

Meloni

et al. 2005

Abstract. Tectonomagnetic field observations from absolute magnetic field levels have been collected in Central Italy since 1989 by means of a network of four absolute magnetometer stations, including the geomagnetic observatory of L'Aquila (42 • 23 N, 13 • 19 E) used as reference for differentiation; also electromagnetic variations from VLF signals have been recorded in the last years by means of VLF search coil wide-band antennas.Many reports proved the occurrence of electromagnetic effects clearly related to tectonic events (seismic and volcanic activity) in active areas of our planet. In this paper we show the variation of some electromagnetic parameters which could be related to local and regional seismic activity for the most recent years 2002 and 2003. We also report the seismic activity recorded in this area by the Italian seismic national network.Some tentative analysis (in the wavelets and statistical approach) on the historical and recent dataset allow a better characterization of electromagnetic properties of the study area, at different temporal and spatial scales.