Investigation of Precursors in VLF Subionospheric Signals Related to Strong Earthquakes (M > 7) in Western China and Possible Explanations
Earthquakes may disturb the lower ionosphere through various coupling mechanisms during their seismogenic and coseismic periods. The VLF signal radiated from ground-based transmitters is affected when it passes near the disturbed region above the seismogenic area, and this anomaly can be recorded by...
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| Format: | Article |
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MDPI AG
2020-10-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/12/21/3563 |
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| author | Shufan Zhao Xuhui Shen Li Liao Zeren Zhima Chen Zhou Zhuangkai Wang Jing Cui Hengxin Lu |
| author_facet | Shufan Zhao Xuhui Shen Li Liao Zeren Zhima Chen Zhou Zhuangkai Wang Jing Cui Hengxin Lu |
| author_sort | Shufan Zhao |
| collection | DOAJ |
| description | Earthquakes may disturb the lower ionosphere through various coupling mechanisms during their seismogenic and coseismic periods. The VLF signal radiated from ground-based transmitters is affected when it passes near the disturbed region above the seismogenic area, and this anomaly can be recorded by ground-based VLF receivers. In this paper, the seismic anomalies before two strong earthquakes (M > 7) that occurred in western China were detected using the ground-based observation of VLF signal; the possible reasons for the anomalies were discussed using full wave simulation. The amplitude of the VLF signals observed by the link between NOV, KHA transmitter, and VLF receivers at Ya’an and Tonghai show obvious anomaly by nighttime fluctuation analysis. The simulated results demonstrate that the anomalies could have been induced by ascending/descending of the bottom height of the ionosphere, caused by depletion/increase in D region electron density. The simulated result also illustrates that terminator time shift could have been induced by descending of the bottom boundary of the ionosphere, which is due to modal interference between different wave modes. |
| first_indexed | 2024-03-10T15:12:31Z |
| format | Article |
| id | doaj.art-fbc4d8d75dd54c488e0244af4caa9201 |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-10T15:12:31Z |
| publishDate | 2020-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-fbc4d8d75dd54c488e0244af4caa92012023-11-20T19:17:11ZengMDPI AGRemote Sensing2072-42922020-10-011221356310.3390/rs12213563Investigation of Precursors in VLF Subionospheric Signals Related to Strong Earthquakes (M > 7) in Western China and Possible ExplanationsShufan Zhao0Xuhui Shen1Li Liao2Zeren Zhima3Chen Zhou4Zhuangkai Wang5Jing Cui6Hengxin Lu7National Institute of Natural Hazards, Ministry of Emergency Management of China, Beijing 100085, ChinaNational Institute of Natural Hazards, Ministry of Emergency Management of China, Beijing 100085, ChinaInstitute of Geophysics, China Earthquake Administration, Beijing 100081, ChinaNational Institute of Natural Hazards, Ministry of Emergency Management of China, Beijing 100085, ChinaSchool of Electronic Information, Wuhan University, Wuhan 430072, ChinaSchool of Electronic Information, Wuhan University, Wuhan 430072, ChinaNational Institute of Natural Hazards, Ministry of Emergency Management of China, Beijing 100085, ChinaNational Institute of Natural Hazards, Ministry of Emergency Management of China, Beijing 100085, ChinaEarthquakes may disturb the lower ionosphere through various coupling mechanisms during their seismogenic and coseismic periods. The VLF signal radiated from ground-based transmitters is affected when it passes near the disturbed region above the seismogenic area, and this anomaly can be recorded by ground-based VLF receivers. In this paper, the seismic anomalies before two strong earthquakes (M > 7) that occurred in western China were detected using the ground-based observation of VLF signal; the possible reasons for the anomalies were discussed using full wave simulation. The amplitude of the VLF signals observed by the link between NOV, KHA transmitter, and VLF receivers at Ya’an and Tonghai show obvious anomaly by nighttime fluctuation analysis. The simulated results demonstrate that the anomalies could have been induced by ascending/descending of the bottom height of the ionosphere, caused by depletion/increase in D region electron density. The simulated result also illustrates that terminator time shift could have been induced by descending of the bottom boundary of the ionosphere, which is due to modal interference between different wave modes.https://www.mdpi.com/2072-4292/12/21/3563precursory of strong earthquakesVLF radio wavenighttime fluctuationseismic anomaliesionospheric disturbancefull-wave model |
| spellingShingle | Shufan Zhao Xuhui Shen Li Liao Zeren Zhima Chen Zhou Zhuangkai Wang Jing Cui Hengxin Lu Investigation of Precursors in VLF Subionospheric Signals Related to Strong Earthquakes (M > 7) in Western China and Possible Explanations Remote Sensing precursory of strong earthquakes VLF radio wave nighttime fluctuation seismic anomalies ionospheric disturbance full-wave model |
| title | Investigation of Precursors in VLF Subionospheric Signals Related to Strong Earthquakes (M > 7) in Western China and Possible Explanations |
| title_full | Investigation of Precursors in VLF Subionospheric Signals Related to Strong Earthquakes (M > 7) in Western China and Possible Explanations |
| title_fullStr | Investigation of Precursors in VLF Subionospheric Signals Related to Strong Earthquakes (M > 7) in Western China and Possible Explanations |
| title_full_unstemmed | Investigation of Precursors in VLF Subionospheric Signals Related to Strong Earthquakes (M > 7) in Western China and Possible Explanations |
| title_short | Investigation of Precursors in VLF Subionospheric Signals Related to Strong Earthquakes (M > 7) in Western China and Possible Explanations |
| title_sort | investigation of precursors in vlf subionospheric signals related to strong earthquakes m 7 in western china and possible explanations |
| topic | precursory of strong earthquakes VLF radio wave nighttime fluctuation seismic anomalies ionospheric disturbance full-wave model |
| url | https://www.mdpi.com/2072-4292/12/21/3563 |
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