2007 Fiscal Year Final Research Report Summary
Ionospheric disturbances by earthquake, volcanic eruption, explosions: Observation with GPS and physical studies
| Project/Area Number |
17540387
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Solid earth and planetary physics
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| Research Institution | Hokkaido University |
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Principal Investigator |
HEKI Kosuke Hokkaido University, Faculty of Science, Professor (30280564)
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| Co-Investigator(Kenkyū-buntansha) |
SAITO Akinori Kyoto University, Graduate School of Science, Assistant Professor (10311739)
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| Project Period (FY) |
2005 – 2007
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| Keywords | Ionospheric disturbance / Global Positioning System / Earthquake / Volcanic eruption / Rocket launch / Solar flare / Total Electron Content (TEC) / Atmospheric waves |
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| Research Abstract |
Ionospheric Total Electron Content (TEC) can be easily measured with the phase differences between the L1 and L2 carrier waves from GPS satellites. TEC disturbances have been offering new views of various phenomena in earth sciences. Recent reports include the directivity and propagation velocity of coseismic ionospheric disturbance (CID) inferred from the 2003 Tokachi-oki earthquake (Heki and Ping, 2005), constraints on the source process of the 2004 Sumatra earthquake with CID waveforms (Heki et al., 2006), energy estimation of the 2004 Asama explosion (Heki, 2006), radio occultation measurement of sudden increase of TEC by solar flares (Heki, 2007), and formation of an ionospheric hole associated with the ascent of H-IIA rocket (Furuya and Heki, 2008).
CIDs are the electron density perturbation at the F2 layer in ionosphere (about 300 km from the ground) driven by acoustic waves that have been excited by vertical crustal movements above the focal region and have propagated upward.. T
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hey appear 10 minutes or so after the earthquake (this is the time required for the wave to propagate from the ground to the F2 layer height). They are characterized by waveforms with periods of 4-5 minutes and with positive (i.e. TEC increase) initial motion, and propagate as fast as -1 km/sec toward south in the northern hemisphere. For rupture of a fault longer than 1000 km, such as the 2004 Sumatra earthquake, CID waveforms become complicated because they are mixtures of CIDs from multiple asperities that ruptured sequentially along the fault in a certain propagation speed. By decoding such waveforms, we could constrain rupture propagation speed and relative magnitudes of asperities. Heki et al. (2006), by analyzing the CID in Thailand and Indonesia after the 2004 Sumatra-Andaman Earthquake, suggested that the rupture propagated as fast as 2.5 km/sec (1.7 km/sec, as suggested by tsunami, is ruled out from the CID point of view) and that the northern Andaman segments did rupture fast enough to excite acoustic wave with periods of 4-5 minutes (tsunamis should have been excited as well although they would have been smaller than in the south). Less
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Research Products
(13 results)
