㧝㧜㧙㧟 ᴒ✽ᧄፉㄭᶏ㧔࿖㗡᧛᧲ᣇᴒ࡮ᴒ᳗⦟ㇱፉ⷏ᣇᴒ㧕ߩ࿕᦭࿾㔡㧔➅ࠅ㄰ߒ࿾㔡 Characteristic Earthquake Sequences near Okinawajima Island (East ofKunigamison Village and West of Okinoerabujima Island)᳇⽎ᐡᴒ✽᳇⽎บ᳇⽎ᐡ࿾㔡੍⍮ᖱႎ⺖᳇⽎ᐡ᳇⽎⎇ⓥᚲ
Okinawa District Meteorological Observatory, JMA
Earthquake Prediction Information Division, JMA
Meteorological Research Institute, JMAᴒ✽࿾ᣇߦ߅޿ߡ㧘ችฎፉㄭᶏߩ࿕᦭࿾㔡 㧔/೨ᓟߩⷙᮨߢᐔဋᐕ㑆㓒ߩ➅ࠅ㄰ߒ࿾㔡㧕ࠍ⏕⹺ߒߚ㓙ߦ㧘᧲ർ࿾ᣇ  㧔ᧄᏎ̪ෳᾖ㧕ߣห᭽㧘ᴒ✽࿾ᣇߩᶏḴဳ࿾㔡ߦ߽࿕᦭࿾㔡߇ᄙᢙሽ࿷ߒߡ޿ࠆน⢻ᕈࠍᜰ៰ߒߚ㧚ਛⷙᮨߩ࿕᦭࿾㔡㧔/㨪/ࠢ࡜ࠬ㧘⊒↢㑆㓒߇ᢙᐕ㨪චᢙᐕ㧕ߩ⺞ᩏ߆ࠄߪ㧘᧲ධᶏ࡮ධᶏ࿾㔡ࠍ฽߻ᄢⷙᮨߥᶏḴဳ࿾㔡㧔/એ਄㧘⊒↢㑆㓒߇ᢙචᐕ㨪ᢙ⊖ᐕߦ㆐ߔࠆߚ߼᷹ⷰ࠺࡯࠲෼㓸߇࿎㔍㧕ߦ߽౒ㅢߔࠆ⍮⷗߇ᓧࠄࠇࠆน⢻ᕈ߇޽ࠆ㧚ߊߦ߇ߺߘࠎߘߎߢ㧘ᴒ✽ᧄፉㄭᶏߩ㧞ߟߩ㗔ၞ㧔࿖㗡᧛ ᧲ᣇᴒ෸߮ᴒ᳗⦟ㇱፉ⷏ᣇᴒ㧕ߦߟ޿ߡ࿾㔡ᵴേࠍ⺞ᩏߒߚ⚿ᨐ㧘࿕᦭࿾㔡ࠍ฽߻․ᓽ⊛ߥ࿾㔡ᵴേ߇⊒↢ߒߡ޿ࠆߎߣ߇ಽ߆ߞߚ㧚ᧄⓂߢߪ㧘࿕᦭࿾㔡 ߣ޿߁⺆ࠍ㧘ࡊ࡟࡯࠻Ⴚ⇇╬ߦሽ࿷ߔࠆ․ቯߩࠕࠬࡍ࡝࠹ࠖ㧔࿕⌕ၞ㧕߇๟ㄝߩṖࠅߦࠃࠅ߶߷หߓᤨ㑆㑆㓒ߢ➅ࠅ㄰ߒ⎕უߐࠇߡ⊒↢ߔࠆหⷙᮨߩ࿾㔡ߢ㧘ߘߩ㗔ၞߢᦨᄢⷙᮨߩ߽ߩࠍᜰߔ⺆ߣߒߡ↪޿ࠆߎߣߣߔࠆ㧚ᧄ⺞ᩏߢߪ㧘‫․ޟ‬ቯߩࠕࠬࡍ࡝࠹ࠖߩ➅ࠅ㄰ߒ⎕უ‫ࠍޠ‬ᬌ಴ߔࠆᚻᲑߣߒߡ㧘⋧ૃ࿾㔡⸃ᨆ෸߮㔡Ḯౣ⸘▚ࠍⴕߞߚ㧚ߔߥࠊߜ㧘ห৻᷹ⷰὐห৻ᚑಽߩ࿾㔡ᵄᒻߩࠦࡅ࡯࡟ࡦࠬ㧔ᵄᒻߩ⋧㑐㧕߇Ყセ⊛㜞޿ⶄᢙߩ࿾㔡ߦߟ޿ߡ㧘ᵄᒻ⋧㑐ࠍ೑↪ߒߚ㔡Ḯౣ⸘▚ࠍⴕ޿㧘ߘࠇࠄߩ㔡Ḯ૏⟎ߩ߫ࠄߟ߈߇㧘࿾㔡ߩⷙᮨ㧔/㧕߆ࠄផቯߐࠇࠆࠕࠬࡍ࡝࠹ࠖߩࠨࠗ࠭ߩౝ஥ߦ෼߹ߞߡ޿ࠆߎߣߩ⏕⹺ࠍߣࠆߎߣߢ㧘ߘࠇࠄߩ࿾㔡ߪ‫ޟ‬ห৻ߩࠕࠬࡍ࡝࠹ࠖߩ⎕უߦࠃࠆ࿾㔡ߢ޽ࠆ‫್ߣޠ‬ᢿߒߚ㧚߹ߚ㧘⋧ૃ࿾㔡ߢ޽ࠆ߆ุ߆ࠍ್ᢿߔࠆ㓙ߦߪ㧘࿾㔡ߩⷙᮨ㧔㧹㧕ߦᔕߓߚථ⿧๟ᦼࠍ⠨ᘦߒߚࡃࡦ࠼ࡄࠬࡈࠖ࡞࠲ࠍㆡ↪ߒ㧘ߎߩߎߣࠍ⏕⹺ߒߡ޿ࠆ㧚ߊߦ߇ߺߘࠎ㧝㧚࿖㗡᧛ ᧲ᣇᴒߩⷫሶဳ࿕᦭࿾㔡㧔╙࿑㧕࿖㗡᧛᧲ᣇᴒߢ㧘ᐕ᦬એ㒠㧘/⒟ᐲߩ࿾㔡߇ᐔဋᐕߩ㑆㓒ߢ࿁⊒↢ߒߡ޿ࠆߎߣࠍ⏕⹺ߒߚ㧔ᐕ᦬ᣣ㧔/㧕㧘ᐕ᦬ᣣ㧔/㧘ᦨᄢ㔡ᐲ㧕㧘ᐕ᦬ᣣ㧔/㧘ᦨᄢ㔡ᐲ㧕㧘ᐕ᦬ᣣ㧔/㧘ᦨᄢ㔡ᐲ㧕㧘ᐕ᦬ᣣ㧔/㧘ᦨᄢ㔡ᐲ㧕㧘ᐕ᦬ᣣ㧔/㧘ᦨᄢ㔡ᐲ㧕㧕㧚ߎࠇࠄߩ࿾㔡ߩ⊒㔡ᯏ᭴㧔ᐕߩ࿾㔡㧘 ⁛ 㒐
ἴ⑼ቇᛛⴚ⎇ⓥᚲߩ(PGVߦࠃࠆ㧕ߪർ⷏㧙ධ᧲ᣇะߦ࿶ജゲࠍᜬߟૐⷺߩㅒᢿጀဳߢ㧘ࡈࠖ࡝ࡇࡦᶏࡊ࡟࡯࠻ߣ㒽ߩࡊ࡟࡯࠻ߩႺ⇇ߢ⊒↢ߒߡ޿ࠆ࿾㔡ߣ⠨߃ࠄࠇࠆ㧚ߐࠄߦ㧘ߎߩ࿾㔡⟲ߩ㨪MO㔌ࠇߚߏߊㄭறߢ㧘߭ߣ࿁ࠅዊߐ޿㧞ࠣ࡞࡯ࡊߩ࿾㔡⟲㧔/෸߮/⒟ᐲ㧕߇ߘࠇߙࠇ೎ߩࠢ࡜ࠬ࠲࡯ࠍᚑߒߡ㧘߶߷๟ᦼ⊛ߦ➅ࠅ㄰ߒ⊒↢ߒߡ޿ࠆߎߣ㧔╙- 417 -࿑ฝ਄㧕߇ಽ߆ߞߚ㧚ߎࠇࠄ㧟ࠣ࡞࡯ࡊߩ࿾㔡⟲ߪ㧘ߘࠇߙࠇߩࠣ࡞࡯ࡊౝߢ࿾㔡ᵄᒻߩࠦࡅ࡯࡟ࡦࠬ୯߇㜞ߊ㧘ߘࠇߙࠇหߓ႐ᚲߢ⊒↢ߒߡ޿ࠆ㧚߹ߚ㧘ㄭறߢ೎ࠣ࡞࡯ࡊߩ࿾㔡߇⊒↢ߔࠆߦ߽߆߆ࠊࠄߕ㧘Ყセ⊛๟ᦼࠍੂߐࠇࠆߎߣߥߊ㧘ߘࠇߙࠇ߶߷หߓᤨ㑆㑆㓒ߢ➅ࠅ㄰ߒ⊒↢ߒߡ޿ࠆࠃ߁ߦ⷗߃ࠆ㧚ߎߩࠃ߁ߦ㧟ࠣ࡞࡯ࡊߣ߽ߘࠇߙࠇหߓ႐ᚲߢหⷙᮨߩ࿾㔡߇߶߷๟ᦼ⊛ߦ⊒↢ߒߡ޿ࠆߎߣ߆ࠄ㧘ࡊ࡟࡯࠻Ⴚ⇇਄ߦሽ࿷ߔࠆ㧟ߟߩㄭធߒߚࠕࠬࡍ࡝࠹ࠖ߇ߘࠇߙࠇ⁛┙ߦ➅ࠅ㄰ߒ⎕უߐࠇߡ㧘ߎࠇࠄߩ࿾㔡ࠍᒁ߈⿠ߎߒߡ޿ࠆߣ⠨߃ࠄࠇࠆ㧚ታ㓙㧘/⒟ᐲߩ࿾㔡ߩߔߴࠅ㊂㧔㨪EO⒟ᐲ  㧕ߪ㧘ߎߩઃㄭߩࡈࠖ࡝ࡇࡦᶏࡊ࡟࡯࠻ߩᴉߺㄟߺߩㅦᐲ㧔ᐕ㑆⚂㨪EO 㧕ߦ⊒↢㑆㓒㧔ᐕ㧕ࠍਸ਼ߓߚ୯ߣห⒟ᐲߢ޽ࠆ㧚ㆊ෰ߩ࿾㔡ߩ⊒↢㑆㓒߆ࠄ㧘ᦝᣂㆊ⒟ዊᮡᧄ⺰ኻᢙᱜⷙಽᏓࡕ࠺࡞㧔ၮḰᣣ㧕ࠍ↪
޿ࠆߣ㧘ᒰ⹥㗔ၞߢߪᰴߩ/ࠢ࡜ࠬߩ࿾㔡߇ᐕ᦬㨪ᐕ᦬ߩ㑆ߦ㧑ߩ⏕₸ߢ⊒↢ߔࠆߣផቯߢ߈ࠆ㧚⏕₸ߩ႐วߪ㧘ᐕ᦬㨪ᐕ᦬ߩ㑆ߢ޽ࠆ㧚㧞㧚ᴒ᳗⦟ㇱፉ⷏ᣇᴒߩ෺ሶဳ࿕᦭࿾㔡㧔╙࿑㧕ᴒ᳗⦟ㇱፉ⷏ᣇᴒߩᷓߐ⚂MOߢߪ㧞ࠣ࡞࡯ࡊߩ➅ࠅ㄰ߒ࿾㔡߇⊒↢ߒߡ߅ࠅ㧘ᐕએ㒠㧘ࠣ࡞࡯ࡊ㧭㧔/⒟ᐲ㧘ᐔဋᐕ㑆㓒㧕߇࿁㧘ࠣ࡞࡯ࡊ㧮㧔/⒟ᐲ㧘ᐔဋᐕ㑆㓒㧕߇࿁⊒↢ߒߡ޿ࠆߎߣࠍ⏕⹺ߒߚ㧔ࠣ࡞࡯ࡊ㧭㧦ᐕ᦬ᣣ㧔/㧕㧘ᐕ᦬ᣣ㧔/㧕㧘ᐕ᦬ᣣ㧔/㧕㧘ᐕ᦬ᣣ㧔/㧕㧘ᐕ᦬ᣣ㧔/㧕㧘ᐕ᦬ᣣ㧔/㧕㧘ࠣ࡞࡯ࡊ㧮㧦ᐕ᦬ᣣ㧔/㧕㧘ᐕ᦬ᣣ㧔/㧕㧘ᐕ᦬ᣣ㧔/㧕㧘ᐕ᦬ᣣ㧔/㧕㧘ᐕ᦬ᣣ㧔/㧕㧘ᐕ᦬ᣣ㧔/㧕㧘ᐕ᦬ᣣ㧔/㧕㧕㧚․ߦ㧘ᐕ㨪ᐕߩ࿾㔡ߪߘࠇߙࠇㅪേߔࠆࠃ߁ߦ⊒↢ߒߡ޿ࠆ㧚⊒㔡ᯏ᭴㧔ᐕߩ࿾㔡ߩ%/6⸃㧕ߪૐⷺߩㅒᢿጀဳߢ㧘ߎࠇࠄߪࡈࠖ࡝ࡇࡦᶏࡊ࡟࡯࠻ߣ㒽ߩࡊ࡟࡯࠻ߩႺ⇇ߢ⊒↢ߒߡ޿ࠆ࿾㔡ߣ⠨߃ࠄࠇࠆ㧚ߐࠄߦ㧘ߎࠇࠄ㧞ࠣ࡞࡯ࡊߩ࿾㔡⟲ߪ㧘ߘࠇߙࠇߩࠣ࡞࡯ࡊౝߢ࿾㔡ᵄᒻߩࠦࡅ࡯࡟ࡦࠬ୯߇㜞ߊ㧔╙࿑Ꮐ㧘╙࿑㧕㧘ߘࠇߙࠇหߓ႐ᚲࠍ㔡Ḯߣߒߡ⊒↢ߒߡ߅ࠅ㧘ߘࠇࠄࠣ࡞࡯ࡊ#㧘$ߩ㔡Ḯߪ㨪MO㔌ࠇߚߏߊㄭறߦ૏⟎ߒߡ޿ࠆ㧔╙࿑ฝ਄㧕ߎߣ߇ಽ߆ߞߚ㧚ߎߩࠃ߁ߦ㧞ࠣ࡞࡯ࡊߣ߽ߘࠇߙࠇหߓ႐ᚲߢหⷙᮨߩ࿾㔡߇߶߷หߓᤨ㑆㑆㓒ߢ⊒↢ߒߡ޿ࠆߎߣ߆ࠄ㧘ࡊ࡟࡯࠻Ⴚ⇇਄ߦሽ࿷ߔࠆ㧞ߟߩㄭធߒߚࠕࠬࡍ࡝࠹ࠖ߇ߘࠇߙࠇ➅ࠅ㄰ߒ⎕უߐࠇߡ㧘ߎࠇࠄߩ࿾㔡ࠍᒁ߈⿠ߎߒߡ޿ࠆߣ⠨߃ࠄࠇࠆ㧚ታ㓙㧘/⒟ᐲߩ࿾㔡ߩߔߴࠅ㊂㧔㨪EO⒟ᐲ  㧕ߪ㧘ߎߩઃㄭߩࡈࠖ࡝ࡇࡦᶏࡊ࡟࡯࠻ߩᴉߺㄟߺߩㅦᐲ㧔ᐕ㑆⚂EO 㧕ߦ⊒↢㑆㓒㧔ᐕ෸߮ᐕ㧕ࠍਸ਼ߓߚ୯ߣห⒟ᐲߢ޽ࠆ㧚ㆊ෰ߩ࿾㔡ߩ⊒↢㑆㓒߆ࠄ㧘ᦝᣂㆊ⒟ዊᮡᧄ⺰ኻᢙᱜⷙಽᏓࡕ࠺࡞㧔ၮḰᣣ㧕ࠍ↪
޿ࠆߣ㧘ᒰ⹥㗔ၞߢߪᰴߩࠣ࡞࡯ࡊ㧭ߩ࿾㔡߇ᐕ᦬㨪ᐕ᦬ߩ㑆ߦ㧘ࠣ࡞࡯ࡊ㧮ߩ࿾㔡߇ᐕ᦬߹ߢߦ㧑ߩ⏕₸ߢ⊒↢ߔࠆߣផቯߢ߈ࠆ㧚⏕₸ߩ႐วߪ㧘ᐕ᦬㨪ᐕ᦬ߣ㧘ၮḰᣣ߆ࠄᐕ᦬߹ߢߢ޽ࠆ㧚㧔ḳᷨഞผ࡮ጊ↰቟ਯ࡮⍹၂␭ਃ࡮㜞ᧁᐽિ࡮ਛ᧛㓷ၮ࡮೨↰ᙗੑ࡮ጟ↰ᱜታ࡮౷჻੗໪శ㧕̪㧦‫᧲ޟ‬ർ࿾ᣇ㧔⑔ፉ⋵޿ࠊ߈ᴒ㧘ጤᚻ⋵⒳Ꮢᴒ㧕ߩ࿕᦭࿾㔡‫ޠ‬㧔᳇⽎ᐡ㧕- 418 -ෳ ⠨ ᢥ ₂᳇⽎ᐡᴒ✽᳇⽎บ߶߆㧘ችฎፉㄭᶏߩ࿕᦭࿾㔡⊛࿾㔡ᵴേ㧘ㅪ⛊ળႎ㧘㧚㐳⼱Ꮉ቟⑲࡮ᯅᧄᔀᄦ࡮⨲㊁ንੑ㓶࡮ศᎹ৻శ࡮ᄢ⷏ᤊม㧦᧲ർ࿾ᣇߦ߅ߌࠆਛⷙᮨ࿾㔡ߩ࿕᦭࿾㔡⊛࿾㔡ᵴേߩᬌ಴㧘࿾㔡㧘㧘㧚3) Uchida, N., T. Matsuzawa, W. L. Ellsworth, K. Imanishi, T. Okada, and A. Hasegawa, Source
parameters of a M4.8 and its accompanying repeating earthquakes off Kamaishi, NE Japan: Implications
for the hierarchical structure of asperities and earthquake cycle, Geophys. Res. Lett., 34, 2007.
4) Shimazaki, K. and T. Nakata, T,

Time-predictable recurrence model for large earthquakes, Geophys.

Res. Lett., 7, 279-298, 1980.
5) Nadeau, R. M. and L. R. Johnson : Seismological studies at Parkfield VI: Moment release rates andestimates of source parameters for small repeating earthquakes, Bill. Seism. Soc. Am., 88, 790-814,1998.
ቝᵤᓼᴦ㧦࿾㔡ቇ㧔╙㧟㧕㧘౒┙಴ᩣᑼળ␠㧘2

7) Seno. T., S. Stein, and A. E. Gripp, A model for the motion of the Philippine Sea plate consistent withNUVEL-1 and geological data, J. Geophys. Res., 98, 17941-17948, 1993.

- 419 -╙1࿑ ࿖㗡᧛᧲ᣇᴒߩ࿕᦭࿾㔡㧔➅ࠅ㄰ߒ࿾㔡㧕Fig.1 Characteristic earthquake sequences east of Kunigamison Village.

- 420 -╙2࿑ ᴒ᳗⦟ㇱፉ⷏ᣇᴒߩ࿕᦭࿾㔡㧔➅ࠅ㄰ߒ࿾㔡㧕Fig.2 Characteristic earthquake sequences west of Okinoerabujima Island.

- 421 -╙3࿑ ᴒ᳗⦟ㇱፉ⷏ᣇᴒߩ࿕᦭࿾㔡㧔➅ࠅ㄰ߒ࿾㔡㧕ߩᵄᒻᲧセFig.3 Comparison of waveforms for repeating earthquakes west of Okinoerabujima Island.

- 422 -