Circularly polarized electric fields associated with seismic waves generated by blasting

Matsushima, Masaki; Honkura, Yoshimori; Kuriki, Mayu; Ogawa, Yasuo

doi:10.1093/gji/ggt110

Cited by 12 publications

(8 citation statements)

References 31 publications

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“…His numerical result showed that the coseismic magnetic field can reach the order of 0.1 nT, which is detectable. Recently, reports on the observed circularly polarized coseismic electric field [ Honkura et al ., ; Kuriki et al ., ; Matsushima et al ., ] provided evidences for the role of the Earth's magnetic field in generating EM disturbances. Moreover, observations of the tsunami‐induced magnetic variations [ Manoj et al ., ; Toh et al ., ; Utada et al ., ; Ichihara et al ., ] were further evidences which indicate that the conductive seawater moving across the Earth's magnetic field can also generate observable variations in the magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Induced electromagnetic field by seismic waves in Earth's magnetic field

Gao

Chen

et al. 2014

JGR Solid Earth

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Studied in this article are the properties of the electromagnetic (EM) fields generated by an earthquake due to the motional induction effect, which arises from the motion of the conducting crust across the Earth's magnetic field. By solving the governing equations that couple the elastodynamic equations with Maxwell equations, we derive the seismoelectromagnetic wavefields excited by a single-point force and a double-couple source in a full space. Two types of EM disturbances can be generated, i.e., the coseismic EM field accompanying the seismic wave and the independently propagating EM wave which arrives much earlier than the seismic wave. Simulation of an M w 6.1 earthquake shows that at a receiving location where the seismic acceleration is on the order of 0.1 m/s 2 , the coseismic electric and magnetic fields are on the orders of 1 μV/m and 0.1 nT, respectively, agreeing with the EM data observed in 2008 M w 6.1 Qingchuan earthquake, China, and indicating that the motional induction effect is effective enough to generate observable EM signal. We also simulated the EM signals observed by Haines et al. (2007) which were called the Lorentz fields and cannot be explained by the electrokinetic effect. The result shows that the EM wave generated by a horizontal force can explain the data well, suggesting that the motional induction effect is responsible for the Lorentz fields. The motional induction effect is compared with the electrokinetic effect, showing the overall conclusion that the former dominates the mechanoelectric conversion under low-frequency and high-conductivity conditions while the latter dominates under high-frequency and low-conductivity conditions.

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Section: Introductionmentioning

confidence: 99%

Induced electromagnetic field by seismic waves in Earth's magnetic field

Gao

Chen

et al. 2014

JGR Solid Earth

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“…In field observations, the EM observation equipment is usually placed nearby the ground surface; for example, at depth less than 1 m. The observed coseismic magnetic signals always show up in the whole seismic arrival time domain (Honkura et al 2000;Karakelian et al 2002a, b;Tang et al 2010;Matsushima et al 2013;Tsutsui 2014). Thus, the behavior of the numerically simulated magnetic signals is evidently different from the field observations.…”

Section: Water-saturated Half-space Porous Modelmentioning

confidence: 97%

“…Among these phenomena, the most frequently reported is coseismic electromagnetic (EM) signals. In contrast with the direct magnetic signals that show up almost at earthquake origin time (Okubo et al 2011), coseismic EM signals show up simultaneously with seismic arrivals (Honkura et al 2000;Nagao et al 2000;Skordas et al 2000;Karakelian et al 2002a, b;Tang et al 2010;Matsushima et al 2013;Tsutsui 2014;Gao et al 2016). This phenomenon may imply some principle of the relationship between natural earthquakes and anomalous EM signals.…”

Section: Introductionmentioning

confidence: 99%

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

Sun

Uyeshima

Ren

et al. 2019

Earth Planets Space

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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 sevenlayer 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.

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“…A variety of explanations for this phenomenon exist, such as piezoelectric origins (Huang 2002) or a seismic dynamo effect, suggesting that the electric signals are induced by a conductive crust vibrating in the Earth's magnetic field (e.g. Honkura et al 2000;Matsushima et al 2013;Gao et al 2014). At present, the most widely accepted explanation is electrokinetic coupling caused by fluid movement relatively to pore surfaces (e.g.…”

Section: Introductionmentioning

confidence: 99%

Quantifying interface responses with seismoelectric spectral ratios

Dzieran

Thorwart

Rabbel

et al. 2019

Geophysical Journal International

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We investigate seismoelectric (SE) signals accompanying seismic waves radiated from earthquake sources. SE signals are mostly generated from compressional portions of seismic waves by electrokinetic coupling. They contain coseismic electric fields travelling with seismic wave velocity and interface response (IR) waves, which originate at layer interfaces and travel with electromagnetic wave speed. IR wave amplitudes are sensitive to contrasts in poroelastic and electric rock parameters. We introduce SE spectral ratios (SESRs) as a tool to evaluate the influence of IRs on the overall SE signal independently of the earthquake source-time function. Based on data from Northern Chile we show that SESRs show a site specific frequency dependence with a trend of decreasing amplitudes towards increasing frequency. Modelling results reveal that the specific frequency dependence of the SESRs is caused by IRs excited at depths of some hundred metres underneath the recording stations. We analyse the SESR sensitivity towards porosity, permeability, fluid salinity and the depth of the interfaces. We verify that observed SESRs can be reproduced through forward modelling and linearized inversion based on realistic subsurface parameters.

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Circularly polarized electric fields associated with seismic waves generated by blasting

Cited by 12 publications

References 31 publications

Induced electromagnetic field by seismic waves in Earth's magnetic field

Induced electromagnetic field by seismic waves in Earth's magnetic field

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

Quantifying interface responses with seismoelectric spectral ratios

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