A possible effect of ionospheric perturbations associated with the Sumatra earthquake, as revealed from subionospheric very‐low‐frequency (VLF) propagation (NWC‐Japan)

2007 ◽  
Vol 28 (13-14) ◽  
pp. 3133-3139 ◽  
Author(s):  
T. Horie ◽  
S. Maekawa ◽  
T. Yamauchi ◽  
M. Hayakawa
Keyword(s):  
Low Frequency ◽  
Sumatra Earthquake ◽  
Ionospheric Perturbations ◽  
Very Low Frequency ◽  
Vlf Propagation

scholarly journals Possible precursor to the March 11, 2011, Japan earthquake: ionospheric perturbations as seen by subionospheric very low frequency/low frequency propagation

2012 ◽  
Vol 55 (1) ◽  
Author(s):  
Masashi Hayakawa ◽  
Yasuhide Hobara ◽  
Yoshihiro Yasuda ◽  
Hiroki Yamaguchi ◽  
Kenji Ohta ◽  
...  
Keyword(s):  
Low Frequency ◽  
Ionospheric Perturbations ◽  
Very Low Frequency

scholarly journals Multi-Experiment Observations of Ionospheric Disturbances as Precursory Effects of the Indonesian Ms6.9 Earthquake on August 05, 2018

2020 ◽  
Vol 12 (24) ◽  
pp. 4050
Author(s):  
Xuemin Zhang ◽  
Yalu Wang ◽  
Mohammed Boudjada ◽  
Jing Liu ◽  
Werner Magnes ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
Electric Field ◽  
Low Frequency ◽  
Ionospheric Disturbances ◽  
Radio Waves ◽  
Ionospheric Perturbations ◽  
Very Low Frequency ◽  
Ion Drift ◽  
Ionospheric Height

Taking the 2018 Ms6.9 Indonesia earthquake as a case study, the ionospheric perturbations in very low frequency (VLF) transmitters recorded by China Seismo-Electromagnetic Satellite (CSES) were mainly investigated, as well as the multi parameters of the plasma and electromagnetic field. The characteristics of electron density (Ne), GPS TEC, ULF electric field, ion drift velocity, and ionosphere height were extracted and compared with the features of the signal-noise ratio (SNR) from VLF transmitters of NWC at the southern hemisphere and JJI at the northern hemisphere. Most disturbances in VLF radio waves occurred along the orbits near the epicenter within 10 days before the earthquake. Along these orbits, we observed simultaneous modulations in the Ne and ULF electric field, as well as the changed ion drifting directions. There was also high spatial correspondence between both SNR and ionospheric height anomalies over the epicentral and its magnetic conjugate regions. Combined with the multi observations, these results suggest that the genesis of perturbations in signals emitted by VLF transmitters on satellite was more likely related to the overlapped electric field in the preparation area of the earthquake.

scholarly journals A study of the behavior of the terminator time shifts using multiple VLF propagation paths during the Pakistan earthquake (<i>M</i> = 7.2) of 18 January 2011

2013 ◽  
Vol 13 (6) ◽  
pp. 1501-1506 ◽  
Author(s):  
S. Ray ◽  
S. K. Chakrabarti
Keyword(s):  
Low Frequency ◽  
Space Physics ◽  
The Other ◽  
Propagation Path ◽  
Very Low Frequency ◽  
Radio Signals ◽  
Propagation Paths ◽  
Vlf Propagation ◽  
Indian Centre

Abstract. On 18 January 2011, at 20:23 UTC, an earthquake of magnitude 7.2 occurred in southwestern Pakistan (latitude 28°44' N, longitude 63°56' E) at a depth of 68 km. We present the results of the analysis of very low frequency (VLF) radio signals, received at three stations located in India. We analyze the VLF signals around this earthquake day and look for possible precursory effects of this earthquake. For our analysis, we use four different VLF propagation paths. These propagation paths are DHO–IERC (Sitapur), VTX–Pune, VTX–ICSP (Indian Centre for Space Physics, Kolkata) and NWC–IERC. We observed significant shifts of the "sunrise terminator time" (SRT) for DHO–IERC and VTX–Pune paths. For DHO–IERC path, the SRT of the VLF signals shifted towards nighttime three days before the earthquake day, and in the case of VTX–Pune path it shifted towards nighttime just one day before the earthquake day. For VTX–Kolkata path, the shift of SRT is four days before the earthquake day, but here the shift is not so strong, somewhere between 2σ and 3σ lines. For the other two paths, namely, DHO–IERC and VTX–Pune, the terminator time shifts crossed the 3σ line. We found no significant shifts of SRT for NWC–IERC propagation path. Higher deviation in the VTX–Pune path as compared to VTX–ICSP path could be due to the proximity of the former to the epicenter. Similarly, DHO–IERC path is over the epicenter while NWC–IERC path is totally away from the epicenter. This could be the reason why the effect in DHO–IERC path is stronger than that in NWC–IERC path.

scholarly journals The Graz seismo-electromagnetic VLF facility

2011 ◽  
Vol 11 (4) ◽  
pp. 1121-1127 ◽  
Author(s):  
K. Schwingenschuh ◽  
G. Prattes ◽  
B. P. Besser ◽  
K. Močnik ◽  
M. Stachel ◽  
...  
Keyword(s):  
Statistical Data ◽  
Environmental Influences ◽  
Low Frequency ◽  
Present System ◽  
Very Low Frequency ◽  
Vlf Propagation ◽  
Operational Modes

Abstract. In this paper we describe the Graz seismo-electromagnetic very low frequency (VLF) facility, as part of the European VLF receiver network, together with the scientific objectives and results from two years operation. After a brief technical summary of the present system – with heritage from a predecessor facility – i.e. hardware, software, operational modes and environmental influences, we discuss results from statistical data and scientific events related to terrestrial VLF propagation over Europe.

The Attenuation of Very Low Frequency Brain Oscillations in Transitions from a Rest State to Active Attention

2009 ◽  
Vol 23 (4) ◽  
pp. 191-198 ◽  
Author(s):  
Suzannah K. Helps ◽  
Samantha J. Broyd ◽  
Christopher J. James ◽  
Anke Karl ◽  
Edmund J. S. Sonuga-Barke
Keyword(s):  
Brain Activity ◽  
Sampling Rate ◽  
Low Frequency ◽  
Future Research ◽  
Adhd Symptoms ◽  
Default Mode ◽  
Very Low Frequency ◽  
Wide Range ◽  
Interference Hypothesis ◽  
Mode Interference

Background: The default mode interference hypothesis ( Sonuga-Barke & Castellanos, 2007 ) predicts (1) the attenuation of very low frequency oscillations (VLFO; e.g., .05 Hz) in brain activity within the default mode network during the transition from rest to task, and (2) that failures to attenuate in this way will lead to an increased likelihood of periodic attention lapses that are synchronized to the VLFO pattern. Here, we tested these predictions using DC-EEG recordings within and outside of a previously identified network of electrode locations hypothesized to reflect DMN activity (i.e., S3 network; Helps et al., 2008 ). Method: 24 young adults (mean age 22.3 years; 8 male), sampled to include a wide range of ADHD symptoms, took part in a study of rest to task transitions. Two conditions were compared: 5 min of rest (eyes open) and a 10-min simple 2-choice RT task with a relatively high sampling rate (ISI 1 s). DC-EEG was recorded during both conditions, and the low-frequency spectrum was decomposed and measures of the power within specific bands extracted. Results: Shift from rest to task led to an attenuation of VLFO activity within the S3 network which was inversely associated with ADHD symptoms. RT during task also showed a VLFO signature. During task there was a small but significant degree of synchronization between EEG and RT in the VLFO band. Attenuators showed a lower degree of synchrony than nonattenuators. Discussion: The results provide some initial EEG-based support for the default mode interference hypothesis and suggest that failure to attenuate VLFO in the S3 network is associated with higher synchrony between low-frequency brain activity and RT fluctuations during a simple RT task. Although significant, the effects were small and future research should employ tasks with a higher sampling rate to increase the possibility of extracting robust and stable signals.

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