Simultaneous infrasonic, seismic, magnetic and ionospheric observations in an earthquake epicentre

Laštovička, Jan; Baše, Jiří; Hruška, František; Chum, Jaroslav; Šindelářová, Tereza; Horálek, Josef; Zedník, Jan; Krasnov, V. M.

doi:10.1016/j.jastp.2010.08.005

Cited by 24 publications

(16 citation statements)

References 32 publications

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“…In addition, the waves were recorded only around the epicenter, thus, the generated acoustic field was far from the plane wave approximation. Consequently, Laštovička et al [2010] had not observed any ionospheric variations by Doppler sounding system. We searched the microbarometer records from 11 March 2011 (using the same microbarometers like Laštovička et al [2010]), but the background noise level was too high to identify any pressure fluctuations that could be associated with Tohoku earthquake and corresponded to the variations of the v z component of the ground motion.…”

Section: Observation and Data Analysismentioning

confidence: 96%

“…There were numerous papers that studied the infrasound waves from earthquakes at the ground [e.g., Donn and Posmentier , 1964; Le Pichon et al , 2002, 2005] and compared them with the vertical component of the ground surface motion [ Watada et al , 2006]. In the Czech Republic, infrasound waves of the earthquake origin were reported by Laštovička et al [2010], who analyzed the infrasound waves excited by a relatively weak earthquake ( M ∼3.6) in its epicenter in the western part of the Czech Republic. This M 3.6 earthquake produced the vertical motion of the ground surface of similar magnitude (peak value was v z = 1.9 mm/s) like in our case, but the frequencies of the ground (air) oscillations were much higher, typically ∼1 Hz up to ∼10 Hz.…”

Section: Observation and Data Analysismentioning

confidence: 99%

“…We searched the microbarometer records from 11 March 2011 (using the same microbarometers like Laštovička et al [2010]), but the background noise level was too high to identify any pressure fluctuations that could be associated with Tohoku earthquake and corresponded to the variations of the v z component of the ground motion. It is necessary to note that the infrasound background noise level increases with decreasing frequency by more than 20 dB per decade [see Laštovička et al , 2010, Figure 6], thus, the background noise for ∼50 s period waves (0.02 Hz) is more than 40 dB higher than for waves at frequencies of several Hz. The infrasound waves originated from the 11 March 2011 Tohoku earthquake that propagated relatively large distances (∼2500 km) from the epicenter, were observed in China [ Hao et al , 2012].…”

Section: Observation and Data Analysismentioning

confidence: 99%

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Ionospheric disturbances (infrasound waves) over the Czech Republic excited by the 2011 Tohoku earthquake

et al. 2012

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[1] A train of large amplitude infrasound wave packets was observed by multipoint Continuous Doppler sounding system in the ionosphere over the Czech Republic on 11 March 2011. It is shown that these infrasound wave packets originated from vertical motion of the ground surface that was caused by arrival of seismic waves generated by the strong Tohoku earthquake. The infrasound wave packets were observed in the ionosphere at heights of $210-220 km about 9 min after the detection of corresponding wave packets on the ground, which is consistent with the calculated time for vertically propagating infrasound waves. Absolute values of cross-correlation coefficients between ionospheric and ground measurements are typically higher than 0.9 (for two wave packets $0.98). The individual wave packets recorded on the ground have different observed horizontal velocities and correspond to different types of seismic waves. A comparison of vertical velocities of ground motion with oscillation velocities of air particles in the ionosphere indicates that almost 1/10 of the infrasound energy flux excited at the ground reached the altitudes of $210-220 km for wave periods longer than $30 s. Estimates of sound attenuation are performed. It is also shown that it is necessary to consider the value of electron density gradient at the reflection height of the sounding radio wave, and air (plasma) compression owing to the infrasound wave to get reasonable estimates of oscillation velocities of air particles from Doppler shift frequencies.

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Section: Observation and Data Analysismentioning

confidence: 96%

Section: Observation and Data Analysismentioning

confidence: 99%

Section: Observation and Data Analysismentioning

confidence: 99%

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Ionospheric disturbances (infrasound waves) over the Czech Republic excited by the 2011 Tohoku earthquake

et al. 2012

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“…Only strong earthquakes which generate seismic waves with sufficiently long periods, approximately longer than 10 s, produce ionospheric responses observable in the ionosphere. The infrasound of periods shorter than about 10 s attenuates below the F2 region heights (~200 km) and is usually not reliably detected by remote sounding [Blanc 1985;Krasnov et al 2007;Lastovicka et al 2010;Occhipinti et al 2010;Rolland et al 2011].…”

Section: Introductionmentioning

confidence: 99%

Ionospheric signatures of the April 25, 2015 Nepal earthquake and the relative role of compression and advection for Doppler sounding of infrasound in the ionosphere

Chum

Liu

Laštovička

et al. 2016

Earth Planets Space

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Ionospheric signatures possibly induced by the Nepal earthquake are investigated far outside the epicentral region in Taiwan (~3700 km distance from the epicenter) and in the Czech Republic (~6300 km distance from the epicenter). It is shown that the ionospheric disturbances were caused by long period,~20 s, infrasound waves that were excited locally by vertical component of the ground surface motion and propagated nearly vertically to the ionosphere. The infrasound waves are heavily damped at the heights of F layer at around 200 km, so their amplitude strongly depends on the altitude of observation. In addition, in the case of continuous Doppler sounding, the value of the Doppler shift depends not only on the advection (up and down motion) of the reflecting layer but also on the compression/ rarefaction of the electron gas and hence on the electron density gradient. Consequently, under significant differences of reflection height of sounding radio waves and partly also under large differences in plasma density gradients, the observed ionospheric response at larger distances from the epicenter can be comparable with the ionospheric response observed at shorter distances, although the amplitudes of causative seismic motions differ by more than one order of magnitude.

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“…Both earthquake accompanying surface shaking and tsunami would excite atmospheric waves. As a contrast to the work of Lastovicka et al [2010], in this paper multi‐instrument data from HF Doppler measurement, infrasound detector, seismic stations, GPS/TEC and geomagnetic stations are used to make a comprehensive study of the effects after this great Tohoku earthquake. Results and new findings on the atmospheric and ionospheric infrasonic waves and geomagnetic variations induced by the ionosphere disturbances are reported and discussed.…”

Section: Introductionmentioning

confidence: 99%

Multi‐instrument observation on co‐seismic ionospheric effects after great Tohoku earthquake

Hao¹,

Xiao²,

Zhang³

2012

J. Geophys. Res.

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[1] In this paper, evidence of quake-excited infrasonic waves is provided first by a multi-instrument observation of Japan's Tohoku earthquake. The observations of co-seismic infrasonic waves are as follows: 1, effects of surface oscillations are observed by local infrasonic detector, and it seems these effects are due to surface oscillation-excited infrasonic waves instead of direct influence of seismic vibration on the detector; 2, these local excited infrasonic waves propagate upwards and correspond to ionospheric disturbances observed by Doppler shift measurements and GPS/TEC; 3, interactions between electron density variation and currents in the ionosphere caused by infrasonic waves manifest as disturbances in the geomagnetic field observed via surface magnetogram; 4, within 4 hours after this strong earthquake, disturbances in the ionosphere related to arrivals of Rayleigh waves were observed by Doppler shift sounding three times over. Two of the arrivals were from epicenter along the minor arc of the great circle (with the second arrival due to a Rayleigh wave propagating completely around the planet) and the other one from the opposite direction. All of these seismo-ionospheric effects observed by HF Doppler shift appear after local arrivals of surface Rayleigh waves, with a time delay of 8-10 min. This is the time required for infrasonic wave to propagate upwards to the ionosphere.

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Simultaneous infrasonic, seismic, magnetic and ionospheric observations in an earthquake epicentre

Cited by 24 publications

References 32 publications

Ionospheric disturbances (infrasound waves) over the Czech Republic excited by the 2011 Tohoku earthquake

Ionospheric disturbances (infrasound waves) over the Czech Republic excited by the 2011 Tohoku earthquake

Ionospheric signatures of the April 25, 2015 Nepal earthquake and the relative role of compression and advection for Doppler sounding of infrasound in the ionosphere

Multi‐instrument observation on co‐seismic ionospheric effects after great Tohoku earthquake

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