Preseismic ionospheric anomalies detected before the 2016 Kumamoto earthquake

Iwata, Tatsuya; Umeno, Ken

doi:10.1002/2017ja023921

Cited by 32 publications

(21 citation statements)

References 28 publications

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“…All of those are caused by strike-slip faults (Japan Meteorological Agency (JMA), 2016a). Some precursors of this EQ series have been reported, including the anomalies of foreshock activity (Kato et al, 2016), groundwater (Sano et al, 2016), ultralow frequency/extremely low frequency magnetic field (Potirakis, Schekotov, et al, 2018;Schekotov et al, 2017), VLF/LF propagation (Potirakis, Asano, et al, 2018), and total electron contents (Iwata & Umeno, 2017).…”

Section: Eq Treated In This Papermentioning

confidence: 99%

Abnormal Gravity Wave Activity in the Stratosphere Prior to the 2016 Kumamoto Earthquakes

2019

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Earthquake (EQ) prediction is an essential topic in recent geophysics and disaster management. In order to explain EQ precursory phenomena, especially the ionospheric perturbations, a few hypotheses have been proposed as the mechanism of lithosphere‐atmosphere‐ionosphere coupling. The most reliable seems to be the atmospheric gravity wave (AGW) hypothesis, because a lot of subionospheric very low frequency (VLF) observations and also ground surface measurements support this hypothesis. However, no direct signature of AGW activity in the middle atmosphere has been yet obtained. So in this study, we have used the ERA5 reanalysis data to investigate the tempo‐spatial evolution of stratospheric AGW activity before a recent huge seismic event of the 2016 Kumamoto EQ on 15 April (Mw7.2). It was found that the AGW potential energy is enhanced significantly during about 1 week before the EQ. The enhancement was mainly distributed around the EQ epicenter and expanded toward eastern Japan. The AGW activity was highest around 11 April, then it calmed down and returned to the background level right before the EQ. These results were compared with the subionospheric VLF observations during the same period, and then the tempo‐spatial evolutions of the lower ionospheric perturbation are found to be very consistent with the stratospheric behavior. The present paper reports on the first finding that the abnormal AGW activity in the stratosphere is detected before a major EQ, and the coincidence of stratospheric AGW activity with VLF subionospheric perturbations provides further support to the AGW hypothesis of the lithosphere‐atmosphere‐ionosphere coupling process.

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Section: Eq Treated In This Papermentioning

confidence: 99%

Abnormal Gravity Wave Activity in the Stratosphere Prior to the 2016 Kumamoto Earthquakes

2019

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“…In this sense, it is worthwhile to investigate the EM phenomena for these Kumamoto events. A variety of different ionosphere-related precursory signatures possibly related to the Kumamoto EQs have already been reported, such as ionospheric anomalies as detected by total electron content (TEC) calculated by GNSS receivers [ 23 ], or GIM-TEC [ 24 ], or GPS-TEC [ 25 ], transient variations on atmospheric and ionospheric parameters [ 26 , 27 ], subionospheric very low frequency (VLF) propagation anomalies [ 28 , 29 ], atmospheric ULF/ELF radiation and ULF depression [ 30 ], criticality in the ground-observed ULF magnetic fields [ 31 ], and intermittency-induced criticality in the VLF subionospheric propagation data [ 32 ].…”

Section: Introductionmentioning

confidence: 99%

Criticality Analysis of the Lower Ionosphere Perturbations Prior to the 2016 Kumamoto (Japan) Earthquakes as Based on VLF Electromagnetic Wave Propagation Data Observed at Multiple Stations

Potirakis

Asano

Hayakawa

2018

Entropy

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Abstract:The perturbations of the ionosphere which are observed prior to significant earthquakes (EQs) have long been investigated and could be considered promising for short-term EQ prediction. One way to monitor ionospheric perturbations is by studying VLF/LF electromagnetic wave propagation through the lower ionosphere between specific transmitters and receivers. For this purpose, a network of eight receivers has been deployed throughout Japan which receive subionospheric signals from different transmitters located both in the same and other countries. In this study we analyze, in terms of the recently proposed natural time analysis, the data recorded by the above-mentioned network prior to the catastrophic 2016 Kumamoto fault-type EQs, which were as huge as the former 1995 Kobe EQ. These EQs occurred within a two-day period (14 April: M W = 6.2 and M W = 6.0, 15 April: M W = 7.0) at shallow depths (~10 km), while their epicenters were adjacent. Our results show that lower ionospheric perturbations present critical dynamics from two weeks up to two days before the main shock occurrence. The results are compared to those by the conventional nighttime fluctuation method obtained for the same dataset and exhibit consistency. Finally, the temporal evolutions of criticality in ionospheric parameters and those in the lithosphere as seen from the ULF electromagnetic emissions are discussed in the context of the lithosphere-atmosphere-ionosphere coupling.

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“…Such examples include the 2016 Kumamoto earthquake. That is also an intraplate earthquake with more than M w 7.0, for which CRA showed some TEC anomalies before the event (Iwata & Umeno, ). Then, a further statistical analysis to other intraplate earthquakes is expected to reveal if a moment magnitude threshold for electromagnetic precursors exists or not and conditions that the electric circuit model is valid.…”

Section: Discussionmentioning

confidence: 99%

Preseismic Ionospheric Anomalies Detected Before the 2016 Taiwan Earthquake

et al. 2019

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On 5 February 2016 (UTC), an earthquake with moment magnitude 6.4 occurred in southern Taiwan, known as the 2016 (Southern) Taiwan earthquake and 2016 Meinong earthquake. In this study, evidences of seismic earthquake precursors for this earthquake event are investigated. Results show that ionospheric anomalies in total electron content (TEC) can be observed before the earthquake. These anomalies were obtained by processing TEC data, where such TEC data are calculated from phase delays of signals observed at densely arranged ground-based stations in Taiwan for Global Navigation Satellite Systems. This shows that such anomalies were detected within 1 hr before the event.

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Preseismic ionospheric anomalies detected before the 2016 Kumamoto earthquake

Cited by 32 publications

References 28 publications

Abnormal Gravity Wave Activity in the Stratosphere Prior to the 2016 Kumamoto Earthquakes

Abnormal Gravity Wave Activity in the Stratosphere Prior to the 2016 Kumamoto Earthquakes

Criticality Analysis of the Lower Ionosphere Perturbations Prior to the 2016 Kumamoto (Japan) Earthquakes as Based on VLF Electromagnetic Wave Propagation Data Observed at Multiple Stations

Preseismic Ionospheric Anomalies Detected Before the 2016 Taiwan Earthquake

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