Numerical simulations to explain the coseismic electromagnetic signals: a case study for a M5.4 aftershock of the 2016 Kumamoto earthquake

Yao Chong Sun, Makoto Uyeshima, Hengxin Ren, Qinghua Huang, Koki Aizawa, Kaori Tsukamoto, Wataru Kanda, Kaori Seki, Takahiro Kishita, Takao Ohminato, Atsushi Watanabe, Jiangjun Ran, Xiaofei Chen

Research output: Contribution to journalArticle

Abstract

Coseismic electromagnetic (EM) signals that appear from the P arrival were observed in a volcanic area during the 2016 Kumamoto earthquake. In this study, we conduct numerical simulations to explain the coseismic EM signals observed for a M5.4 aftershock of the earthquake. Initially, we adopt a water-saturated half-space model, and its simulation result for a receiver with a depth of 0.1 m suggests that the magnetic signals do not show up at the arrivals of P, refracted SV–P and Rayleigh waves because the evanescent EM waves just counterbalance the localized magnetic signals that accompany P, refracted SV–P and Rayleigh waves. Then, we conduct numerical simulations on a seven-layer half-space model in which the second layer corresponds to an aquifer analogy and the six other layers refer to air-saturated porous media. When only the electrokinetic effect is considered, the simulated coseismic magnetic signals still appear from the S arrival. The combination of electrokinetic effect and surface-charge assumption is also tested. We find that signals before the S arrival are missing on the transverse seismic, transverse electric, radial magnetic and vertical magnetic components, although the situation on horizontal magnetic components is improved to an extent. Then, we introduce an artificial scattering effect into our numerical simulations given that the scattering effect should exist in the volcanic area. New numerical result shows good agreement with the observation result on the signal appearance time. Hence, the combination of electrokinetic and scattering effects is a plausible explanation of coseismic EM signals. Further investigations indicate that coseismic electric and/or magnetic signals are more sensitive to the scattering effect and the aquifer thickness than seismic signals.[Figure not available: see fulltext.]

Original languageEnglish
Article number143
Journalearth, planets and space
Volume71
Issue number1
DOIs
Publication statusPublished - Dec 1 2019

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aftershock
magnetic signals
earthquakes
electromagnetism
earthquake
arrivals
electrokinetics
refracted waves
simulation
aquifers
Rayleigh waves
half spaces
scattering
volcanology
counterbalances
Rayleigh wave
half space
aquifer
electromagnetic radiation
receivers

All Science Journal Classification (ASJC) codes

  • Geology
  • Space and Planetary Science

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Numerical simulations to explain the coseismic electromagnetic signals : a case study for a M5.4 aftershock of the 2016 Kumamoto earthquake. / Sun, Yao Chong; Uyeshima, Makoto; Ren, Hengxin; Huang, Qinghua; Aizawa, Koki; Tsukamoto, Kaori; Kanda, Wataru; Seki, Kaori; Kishita, Takahiro; Ohminato, Takao; Watanabe, Atsushi; Ran, Jiangjun; Chen, Xiaofei.

In: earth, planets and space, Vol. 71, No. 1, 143, 01.12.2019.

Research output: Contribution to journalArticle

Sun, YC, Uyeshima, M, Ren, H, Huang, Q, Aizawa, K, Tsukamoto, K, Kanda, W, Seki, K, Kishita, T, Ohminato, T, Watanabe, A, Ran, J & Chen, X 2019, 'Numerical simulations to explain the coseismic electromagnetic signals: a case study for a M5.4 aftershock of the 2016 Kumamoto earthquake', earth, planets and space, vol. 71, no. 1, 143. https://doi.org/10.1186/s40623-019-1122-7
Sun, Yao Chong ; Uyeshima, Makoto ; Ren, Hengxin ; Huang, Qinghua ; Aizawa, Koki ; Tsukamoto, Kaori ; Kanda, Wataru ; Seki, Kaori ; Kishita, Takahiro ; Ohminato, Takao ; Watanabe, Atsushi ; Ran, Jiangjun ; Chen, Xiaofei. / Numerical simulations to explain the coseismic electromagnetic signals : a case study for a M5.4 aftershock of the 2016 Kumamoto earthquake. In: earth, planets and space. 2019 ; Vol. 71, No. 1.
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AU - Uyeshima, Makoto

AU - Ren, Hengxin

AU - Huang, Qinghua

AU - Aizawa, Koki

AU - Tsukamoto, Kaori

AU - Kanda, Wataru

AU - Seki, Kaori

AU - Kishita, Takahiro

AU - Ohminato, Takao

AU - Watanabe, Atsushi

AU - Ran, Jiangjun

AU - Chen, Xiaofei

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N2 - Coseismic electromagnetic (EM) signals that appear from the P arrival were observed in a volcanic area during the 2016 Kumamoto earthquake. In this study, we conduct numerical simulations to explain the coseismic EM signals observed for a M5.4 aftershock of the earthquake. Initially, we adopt a water-saturated half-space model, and its simulation result for a receiver with a depth of 0.1 m suggests that the magnetic signals do not show up at the arrivals of P, refracted SV–P and Rayleigh waves because the evanescent EM waves just counterbalance the localized magnetic signals that accompany P, refracted SV–P and Rayleigh waves. Then, we conduct numerical simulations on a seven-layer half-space model in which the second layer corresponds to an aquifer analogy and the six other layers refer to air-saturated porous media. When only the electrokinetic effect is considered, the simulated coseismic magnetic signals still appear from the S arrival. The combination of electrokinetic effect and surface-charge assumption is also tested. We find that signals before the S arrival are missing on the transverse seismic, transverse electric, radial magnetic and vertical magnetic components, although the situation on horizontal magnetic components is improved to an extent. Then, we introduce an artificial scattering effect into our numerical simulations given that the scattering effect should exist in the volcanic area. New numerical result shows good agreement with the observation result on the signal appearance time. Hence, the combination of electrokinetic and scattering effects is a plausible explanation of coseismic EM signals. Further investigations indicate that coseismic electric and/or magnetic signals are more sensitive to the scattering effect and the aquifer thickness than seismic signals.[Figure not available: see fulltext.]

AB - Coseismic electromagnetic (EM) signals that appear from the P arrival were observed in a volcanic area during the 2016 Kumamoto earthquake. In this study, we conduct numerical simulations to explain the coseismic EM signals observed for a M5.4 aftershock of the earthquake. Initially, we adopt a water-saturated half-space model, and its simulation result for a receiver with a depth of 0.1 m suggests that the magnetic signals do not show up at the arrivals of P, refracted SV–P and Rayleigh waves because the evanescent EM waves just counterbalance the localized magnetic signals that accompany P, refracted SV–P and Rayleigh waves. Then, we conduct numerical simulations on a seven-layer half-space model in which the second layer corresponds to an aquifer analogy and the six other layers refer to air-saturated porous media. When only the electrokinetic effect is considered, the simulated coseismic magnetic signals still appear from the S arrival. The combination of electrokinetic effect and surface-charge assumption is also tested. We find that signals before the S arrival are missing on the transverse seismic, transverse electric, radial magnetic and vertical magnetic components, although the situation on horizontal magnetic components is improved to an extent. Then, we introduce an artificial scattering effect into our numerical simulations given that the scattering effect should exist in the volcanic area. New numerical result shows good agreement with the observation result on the signal appearance time. Hence, the combination of electrokinetic and scattering effects is a plausible explanation of coseismic EM signals. Further investigations indicate that coseismic electric and/or magnetic signals are more sensitive to the scattering effect and the aquifer thickness than seismic signals.[Figure not available: see fulltext.]

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