TY - JOUR
T1 - Numerical simulations to explain the coseismic electromagnetic signals
T2 - a case study for a M5.4 aftershock of the 2016 Kumamoto earthquake
AU - Sun, Yao Chong
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
N1 - Funding Information:
The authors acknowledge the use of Focal Mechanism Catalog from NIED. The main part of this work was carried out when Dr. Ren was visiting ERI, The University of Tokyo in 2017. Dr. Ren very much appreciates the warm-hearted help and important supports from International Research Promotion Office of ERI during that period. All the authors appreciate the excellent review work of the two anonymous reviewers.
Funding Information:
This study was supported by the National Natural Science Foundation of China (Grant numbers 41674074, 41874082, 41790465 and 41904046). This study was also supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, under its “Earthquake and Volcano Hazards Observation and Research Program” and “Integrated Program for Next Generation Volcano Research and Human Resource Development”.
Publisher Copyright:
© 2019, The Author(s).
PY - 2019/12/1
Y1 - 2019/12/1
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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U2 - 10.1186/s40623-019-1122-7
DO - 10.1186/s40623-019-1122-7
M3 - Article
AN - SCOPUS:85077158475
VL - 71
JO - Earth, Planets and Space
JF - Earth, Planets and Space
SN - 1343-8832
IS - 1
M1 - 143
ER -