Anomalous variations of VLF sub-ionospheric signal and Mesospheric Ozone prior to 2015 Gorkha Nepal Earthquake

Phanikumar, D. V.; Maurya, Amit Kumar; Kumar, Kondapalli Niranjan; Venkatesham, K.; Singh, Rajesh; Sharma, Sarita; Naja, Manish

doi:10.1038/s41598-018-27659-9

Cited by 23 publications

(19 citation statements)

References 35 publications

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“…The ground velocity data within a time span of one year from all the seismic stations were filtered by using a bandpass filter of 8 × 10 −5 -2 × 10 −4 Hz (i.e., a period of 1.5-3.5 h). Strong peak values, which are caused by unwanted influences (i.e., artificial noise, local earthquakes, teleseismic waves and so on), were mitigated through the summation of the filtered amplitudes as a daily value [29]. The summated daily values at all the stations were processed through the PCA method, to extract common-mode ground vibrations during the Meinong earthquake.…”

Section: Methodsmentioning

confidence: 99%

Determination of Epicenters before Earthquakes Utilizing Far Seismic and GNSS Data: Insights from Ground Vibrations

Chen

Yeh

et al. 2020

Remote Sensing

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Broadband seismometers, ground-based Global Navigation Satellite Systems (GNSS), and magnetometers that were located within an epicentral distance of approximately 150 km consistently observed the novel anomalous behaviors of the common-mode ground vibrations approximately 5–10 days before the M6.6 Meinong earthquake in Taiwan. The common-mode ground vibrations with amplitudes near 0.1 m at frequencies ranging from 8 × 10−5 to 2 × 10−4 Hz were generated near the region close to the epicenter of the impending earthquake. The common-mode vibrations were consistently observed in seismic and GNSS data associated with five other earthquakes in four distinct areas. The results reveal that the common-mode vibrations could be a typical behavior before earthquakes. The causal mechanism of common-mode vibrations can be attributed to crustal resonance excitations before fault dislocations occur. Potential relationships with other pre-earthquake anomalies suggest that the common-mode vibrations could be ground motion before earthquakes, which was investigated for a significant length of time.

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Section: Methodsmentioning

confidence: 99%

Determination of Epicenters before Earthquakes Utilizing Far Seismic and GNSS Data: Insights from Ground Vibrations

Chen

Yeh

et al. 2020

Remote Sensing

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“…Ref. [ 40 ] have reported the depletion (enhancement) of ozone concentration in the lower (upper) mesosphere before the 2015 Gorkha Nepal EQ. We are also interested in the variation in the upper stratospheric ozone before the 2011 Tohoku EQ, since we have found the anomalies of stratopause in the present study.…”

Section: The Response Of the Stratopause To The Precursory Agw Actmentioning

confidence: 99%

“…and AGW (10–100 min.) components in the ground motions [ 34 ], short-term crustal movements [ 35 ] (which also accompany the generation of seismic electric signals [ 36 , 37 ]), the fluctuations in the AGW range in surface atmospheric pressure as well as ULF magnetic field [ 38 , 39 ], and anomalies in the mesospheric ozone density [ 40 ]. These papers provide certain evidence to the AGW hypothesis in the LAIC process.…”

Section: Introductionmentioning

confidence: 99%

Gravity Wave Activity in the Stratosphere before the 2011 Tohoku Earthquake as the Mechanism of Lithosphere-atmosphere-ionosphere Coupling

Yang

Hayakawa

2020

Entropy

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The precursory atmospheric gravity wave (AGW) activity in the stratosphere has been investigated in our previous paper by studying an inland Kumamoto earthquake (EQ). We are interested in whether the same phenomenon occurs or not before another major EQ, especially an oceanic EQ. In this study, we have examined the stratospheric AGW activity before the oceanic 2011 Tohoku EQ (Mw 9.0), while using the temperature profiles that were retrieved from ERA5. The potential energy (EP) of AGW has enhanced from 3 to 7 March, 4–8 days before the EQ. The active region of the precursory AGW first appeared around the EQ epicenter, and then expanded omnidirectionally, but mainly toward the east, covering a wide area of 2500 km (in longitude) by 1500 km (in latitude). We also found the influence of the present AGW activity on some stratospheric parameters. The stratopause was heated and descended; the ozone concentration was also reduced and the zonal wind was reversed at the stratopause altitude before the EQ. These abnormalities of the stratospheric AGW and physical/chemical parameters are most significant on 5–6 March, which are found to be consistent in time and spatial distribution with the lower ionospheric perturbation, as detected by our VLF network observations. We have excluded the other probabilities by the processes of elimination and finally concluded that the abnormal phenomena observed in the present study are EQ precursors, although several potential sources can generate AGW activities and chemical variations in the stratosphere. The present paper shows that the abnormal stratospheric AGW activity has also been detected even before an oceanic EQ, and the AGW activity has obliquely propagated upward and further disturbed the lower ionosphere. This case study has provided further support to the AGW hypothesis of the lithosphere-atmosphere-ionosphere coupling process.

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“…Moreover, Kamiyama et al () have examined the crustal movements based on the Global Positioning System data during the 2011 Tohoku EQ (M9.0) and concluded that the short‐term preseismic crustal movements are closely correlated in time with VLF/LF subionospheric and ultralow frequency magnetic field precursors, which have been reported by some previous papers (Hayakawa, Hobara, et al, ; Hayakawa et al, ; Hayakawa, Rozhnoi, et al, ; Ohta et al, ; Schekotov et al, ). Recently, Phanikumar et al () have used both ground‐based VLF observations and mesospheric ozone data observed by Thermosphere, Ionosphere, Mesosphere Energetics, and Dynamics satellite, to study the preseismic effects during the 2015 Gorkha Nepal EQ (M7.8) and its largest aftershock (M7.3). The VLF signal and mesospheric ozone density (at the same altitude as the VLF reflection height) are anomalous simultaneously before the EQ day in both shocks.…”

Section: Introductionmentioning

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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Anomalous variations of VLF sub-ionospheric signal and Mesospheric Ozone prior to 2015 Gorkha Nepal Earthquake

Cited by 23 publications

References 35 publications

Determination of Epicenters before Earthquakes Utilizing Far Seismic and GNSS Data: Insights from Ground Vibrations

Determination of Epicenters before Earthquakes Utilizing Far Seismic and GNSS Data: Insights from Ground Vibrations

Gravity Wave Activity in the Stratosphere before the 2011 Tohoku Earthquake as the Mechanism of Lithosphere-atmosphere-ionosphere Coupling

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

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