Direct magnetic signals from earthquake rupturing: Iwate-Miyagi earthquake of M 7.2, Japan

Okubo, Kan; Takeuchi, Nobunao; Utsugi, Mitsuru; Yumoto, K.; Sasai, Yoichi

doi:10.1016/j.epsl.2011.02.042

Cited by 37 publications

(39 citation statements)

References 14 publications

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“…However, the magnetic field changes are very small variations of 300pT [4]. The our successful result is observed by geomagnetic observation system with flux-gate magnetometer(10Hz sampling rate) and a synchronized accelerometer.…”

Section: Introductionmentioning

confidence: 79%

“…By our continuous observation, our research group also reported a successful result which is "co-faulting" Earth's magnetic field variation due to piezomagnetic effects caused by earthquake rupturing (i.e., EQ-piezomagnetic effects) in 2008 Iwate-Miyagi Nairiku earthquake of M7.2 [4].…”

Section: Introductionmentioning

confidence: 92%

“…If we can detect an earthquake from magnetic field, we are able to early warn the occurrence. Further efforts could lead us to a new system for super-early warning of earthquake detection with the magnetic signal [4].…”

Section: Introductionmentioning

confidence: 99%

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High-resolution geomagnetic observation system using HTS-SQUID

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Abstract:Our research group reported successful observation of "co-faulting" Earth's magnetic field changes due to piezomagnetic effects caused by earthquake rupturing in 2008 Iwate-Miyagi Nairiku earthquake of M7.2 using geomagnetic observation system with fluxgate magnetometers. This is an important finding; the electromagnetic fields propagate from the sources to the observation site at speed of ca. 3.0 × 10 8 m/s in the crustal materials. Further efforts could lead us to a new system for super-early warning of earthquake detection with the geomagnetic signal. On the other hand, the observed result with the earthquake was suggested that the geomagnetic field change accompanying fault movement, whose sources are the piezomagnetic effects, is very small and short term; therefore development of a high-resolution magnetometer system is very important. To solve this problem, we first developed long-term precise geomagnetic observations using high-temperature-superconductor based superconductingquantum-interference-device (HTS-SQUID) magnetometer system. The HTS-SQUID magnetometer system had never achieved for high-resolution geomagnetic observations in outdoor field. Since March 2012, we have observed the geomagnetic field using a first HTS-SQUID magnetometer at Iwaki observation site (IWK) in Fukushima, Japan. In this study, comparison between the introduced HTS-SQUID magnetometer and conventional flux-gate clarified that the HTS-SQUID magnetometer in our system has higher resolution of magnetic field observation.

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Section: Introductionmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 92%

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High-resolution geomagnetic observation system using HTS-SQUID

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“…b. Co-faulting signals: Quasi-static electromagnetic changes, probably with further strong amplitudes, appear from the focal zone during failure (Figure 19b). Although detection of such direct signals using scientific evidence is very rare, probably for the reasons described above, one report describes that fluxgate magnetometers at (H) Hosokura site detected changes in the geomagnetic field during failure (Okubo et al, 2011). On the other hand, seismic waves induce pore water oscillation in the near-surface sediment layer and cause the streaming potential.…”

Section: Discussionmentioning

confidence: 99%

“…However, we developed the underground observation site, (H) Hosokura. Now this site has various other sensors: an electric field mill, two air ion counters (for positive and negative ions), an air temperature-humidity probe, reference electrodes, and two fluxgate magnetometers (Takeuchi et al, 2009;Okubo et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

Electric and Electromagnetic Signals Under, on, and Above the Ground Surface at the Arrival of Seismic Waves

Takeuchi¹,

Okubo²,

Takeuchi³

2012

Seismic Waves - Research and Analysis

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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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Direct magnetic signals from earthquake rupturing: Iwate-Miyagi earthquake of M 7.2, Japan

Cited by 37 publications

References 14 publications

High-resolution geomagnetic observation system using HTS-SQUID

High-resolution geomagnetic observation system using HTS-SQUID

Electric and Electromagnetic Signals Under, on, and Above the Ground Surface at the Arrival of Seismic Waves

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

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