Observation of Ultra-Low-Frequency Wave Effects in Possible Association with the Fukushima Earthquake on 21 November 2016, and Lithosphere–Atmosphere–Ionosphere Coupling
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Published:2023-08-07
Issue:8
Volume:14
Page:1255
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ISSN:2073-4433
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Container-title:Atmosphere
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language:en
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Short-container-title:Atmosphere
Author:
Hayakawa Masashi12, Schekotov Alexander3ORCID, Yamaguchi Hiroki4, Hobara Yasuhide56
Affiliation:
1. Hayakawa Institute of Seismo Electromagnetics Co., Ltd. (Hi-SEM), UEC (The University of Electro-Communications) Alliance Center #521, 1-1-1 Kojima-cho, Chofu 182-0026, Japan 2. Advanced & Wireless Communications Research Center (AWCC), The University of Electro-Communications (UEC), 1-5-1 Chofugaoka, Chofu 182-8585, Japan 3. The Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, 10-1 Gruzinskaya, Moscow 123242, Russia 4. Fuji DR Security Co., Ltd., 9 Iwato-cho, Shinjuku, Tokyo 162-0832, Japan 5. Department of Computer and Network Engineering, The University of Electro-Communications (UEC), 1-5-1 Chofugaoka, Chofu 182-8585, Japan 6. Center for Space Sciences and Radio Engineering, The University of Electro-Communications (UEC), 1-5-1 Chofugaoka, Chofu 182-8585, Japan
Abstract
The study presents seismogenic ULF (ultra-low-frequency) wave effects, as observed at our own new magnetic observatory at Asahi (geographic coordinates: 35.770° N, 140.695° E) in Chiba Prefecture. Our target earthquake (EQ) is a huge one offshore of Fukushima prefecture (37.353° N, 141.603° E) with a magnitude (M) of 7.4, which occurred at 20.59 h on November 21 UT, 2016. As a sampling frequency of 1 Hz was chosen for our induction magnetometer, we could detect both ULF wave effects: ULF radiation from the lithosphere, and the ULF depression effect, indicative of lower ionospheric perturbations. Observing the results of polarization analyses, we detected clear enhancements in ULF (frequency = 0.01–0.03 Hz) lithospheric radiation 14 days, 5 days, and 1 day before the EQ, and also observed a very obvious phenomenon of ULF (0.01–0.03 Hz) depression just 1 day prior to the EQ, which is regarded as the signature of lower ionospheric perturbations. These findings suggest that pre-EQ seismic activity must be present in the lithosphere, and also that the lower ionosphere was very much perturbed by the precursory effects of the Fukushima EQ. These new observational effects from our station have been compared with our previous investigations on different seismogenic topics for the same EQ, including the ULF observations at another magnetic observatory at Kakioka, belonging to the Japan Meteorological Agency (JMA), about 50 km north of our Asahi station, subionospheric VLF/LF propagation data (Japanese and Russian data), AGW (Atmospheric gravity wave) activity in the stratosphere, and satellite observation of particle precipitations. We have found that seismogenic anomalies of different parameters tend to happen just around the EQ day, but mainly before the EQ, and have found the chain-like tendency of the effects of the lithosphere, which seem to propagate upwards the lower ionosphere. Finally, we will try to gain a better understanding of the physical phenomena or mechanisms of the lithosphere–atmosphere–ionosphere coupling (LAIC) process during the EQ preparation phase.
Subject
Atmospheric Science,Environmental Science (miscellaneous)
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