 
1⿥ૐ๟ᵄ࿾㔡ߩᵴേߦၮߠߊࡊ࡟࡯࠻㑆࿕⌕ߩផቯ⿥ૐ๟ᵄ࿾㔡ߩᵴേߦၮߠߊࡊ࡟࡯࠻㑆࿕⌕ߩផቯ- Characteristics of shallower slow earthquakes occurring near the trench ᦭ศ ᘮ੺*1࡮᧻Ỉ ᥰ*2࡮ᣣ㊁ ੫ᄥ*2࡮㐳⼱Ꮉ ᤘ*2
ၳ 㜞ፄ*1࡮ਛ↰ ઎ሶ*1࡮㊄↰ ⟵ⴕ*1*1⁛┙ⴕ᡽ᴺੱ ᶏᵗ⎇ⓥ㐿⊒ᯏ᭴ ࿾㔡ᵤᵄ࡮㒐ἴ⎇ⓥࡊࡠࠫࠚࠢ࠻

*2᧲ർᄢቇᄢቇ㒮ℂቇ⎇ⓥ⑼㒝ዻ ࿾㔡࡮ྃἫ੍⍮⎇ⓥ᷹ⷰ࠮ࡦ࠲࡯ ᵻㇱ⿥ૐ๟ᵄ࿾㔡ߪ㧘ߎࠇ߹ߢ⷏ධᣣᧄ߿චൎᴒߢߒ߆ᝒ߃ࠄࠇߡߎߥ߆ߞߚ߇㧘᧲ർ࿾ᣇᄥᐔᵗᴒ࿾㔡ᓟߩ⹦⚦ߥ⸃ᨆߦࠃࠅ㧘᧲ർᴒߢ߽⊒↢ߒߡ޿ࠆߎߣ߇⏕߆߼ࠄࠇߚ㧚ߘߎߢᧄ⎇ⓥߢߪ㧘ᢙ୯ࠪࡒࡘ࡟࡯࡚ࠪࡦߦၮߠ޿ߡ㧘ᵻㇱ⿥ૐ๟ᵄ࿾㔡ߩᵴേߣࡊ࡟࡯
࠻㑆࿕⌕ߣߩ㑐ଥࠍ⺞ߴ㧘ߘߩ⚿ᨐࠍ᧲ർ࿾ᣇᄥᐔᵗᴒ࿾㔡߳ㆡ↪ߔࠆߎߣࠍ⹜ߺߚ㧚㧝㧚ߪߓ߼ߦ㧝㧚ߪߓ߼ߦ
ධᶏ࠻࡜ࡈᴪ޿ߢ⊒↢ߔࠆ ”ࠁߞߊࠅ࿾㔡” ߩ৻⒳ߢ޽ࠆ⿥ૐ๟ᵄ࿾
㔡 [1] ߪ㧘30km ߩ╬ᷓ✢਄ߦ߶߷ಽᏓߒߡ޿ࠆߛߌߢߥߊ㧘ᶏḴઃㄭߢ߽⊒↢ߒߡ޿ࠆߎߣ߇㧘ᦨㄭߩᶏᐩ᷹ⷰ߆ࠄ᣿ࠄ߆ߣߥߞߚ [2]㧚ߘߎߢ㧘᦭ศ࡮ઁ [3] ߢߪ㧘ㄭ޿዁᧪⿠߈ࠆߣߐࠇࠆ᧲ධᶏ࿾㔡ߩ೨ᓟߢ㧘⿥ૐ๟ᵄ࿾㔡ߩᵴേ߳ߩᓇ㗀ࠍ⺞ߴߚ⚿ᨐ㧘ᷓㇱࠃࠅᵻㇱߩᣇ߇㧘ᵴേߩᄌൻ߇ᄢ߈ߊߥࠆߎߣࠍᜰ៰ߒߚ㧚ߒ߆ߒ㧘ߎߎߢᗐቯߒߚᶏḴဳᏂᄢ࿾㔡ߪ㧘⚂ 100 ᐕߦ㧝࿁ߩ㗫ᐲߢ⊒↢ߒ㧘ࡊ࡟࡯࠻㑆ߩᐔဋ࿕⌕₸߽㧠ഀ⒟ᐲߣߥߞߡ߅ࠅ㧘᧲ർ࿾ᣇᄥᐔᵗᴒ࿾㔡ߢᶏḴઃㄭߦᏂᄢߔߴࠅࠍ߽ߚࠄߒߚ㧘ᶏḴઃㄭ߹ߢ⓭߈࿑㧝㧚᧲ർ࿾ᣇᄥᐔᵗᴒ࿾㔡ߦ߅ߌࠆ࿾㔡ᤨߔߴࠅಽᛮߌߚ࿾㔡ᕈߔߴࠅ߇ౣ⃻಴᧪ߡᏓߩផቯ⚿ᨐߩ৻଀ [4]㧚޿ߥ޿ (࿑㧝)㧚

  


2 ߘߎߢᧄ⎇ⓥߢߪ㧘ᶏḴ߹ߢ࿾㔡ᕈߔߴࠅ߇⓭߈ᛮߌࠆ߶ߤᒝߊ࿕⌕ߔࠆ႐วߣ࿾㔡ᕈߔߴࠅ߇ᶏḴ߹ߢ⓭߈ᛮߌߥ޿ᒙ޿࿕⌕ߩ႐วߦߟ޿ߡ㧘ᄢⷙᮨߥᢙ୯ࠪࡒࡘ࡟࡯࡚ࠪࡦߩ⸘▚⚿ᨐࠍᲧセߒ㧘ᵻㇱ⿥ૐ๟ᵄ࿾㔡ߩᵴേᄌൻߩ․ᓽߦߟ޿ߡߩ᛽಴ࠍ⹜ߺࠆ㧚㧞㧚ᶏḴဳᏂᄢ࿾㔡ߩࡕ࠺࡞ൻ㧞㧚ᶏḴဳᏂᄢ࿾㔡ߩࡕ࠺࡞ൻ ࡊ࡟࡯࠻㑆࿕⌕ߩലᨐࠍᲧセߔࠆߚ߼㧘⸘▚ᚻᴺ߿ᗐቯࡄ࡜ࡔ࠲࡯୯ߪ㧘೨࿁ [3] ߣ౒ㅢߦߒߚ㧚ᧄ⎇ⓥߢߪ㧘ㅦᐲ࡮⁁ᘒଐሽ៺ᡂ᭴ᚑೣߩ߁ߜ㧘ࠁߞߊࠅ࿾㔡ߩ⊒↢⃻⽎ࠍౣ⃻ߒᤃ޿ slowness-law ࠍㆡ↪ߒߚ [5]㧚៺ᡂ቟ቯᕈߩⓨ㑆ಽᏓࠍ࿑㧞ߦ␜ߔ㧚ߎߎߢߪᏂᄢ
ࠕࠬࡍ࡝࠹ࠖߩ៺ᡂ․ᕈ (b ୯) ࠍᄌ߃ࠆߎߣߦࠃߞߡ㧘࿕⌕ᒝᐲ߇⇣ߥࠆ㧞ߟߩࡕ࠺࡞ࠍ᭴▽ߒߚ㧚ߎߩ㧞ߟߩࡕ࠺࡞ߦߟ޿ߡ㧘ᧄ⎇ⓥߢߪ㧘 strong coupling model, weak couplingmodel ߣ๭߱ߎߣߦߔࠆ㧚࿑㧞㧚strong coupling model ߦ߅ߌࠆ៺ᡂ቟ቯᕈߩⓨ㑆ಽᏓ࿑㧚ᥦ⦡♽ߪ៺ᡂ቟ቯ (☼ᕈ⊛ߥߔߴࠅ․ᕈ)㧘ኙ⦡♽ߪ៺ᡂਇ቟ቯ (࿕⌕ߣ࿾㔡ᕈߔߴࠅߩ➅ࠅ㄰ߒ) ࠍ␜ߔ㧚ᄢ߈ߥᬦ౞ၞౝߪᶏḴဳᏂᄢ࿾㔡ߩ㔡Ḯၞߦ⋧ᒰߒ㧘strong / weak (coupling model) ߦ߅޿ߡ㧘 ߩ୯
ߪ㧘-3.8 / 9.8 [10-4] ߣߒߚ㧚weak coupling model ߦߟ޿ߡߪ㧘ోߡߩ౉ജࡄ࡜ࡔ࠲࡯ߪ೨
࿁ [3] ߣోߡห৻ߣߥߞߡ޿ࠆ㧚 

!"#$%&'()*+

3㧟㧚ࡊ࡟࡯࠻㑆࿕⌕ߩᒝᒙߦၮߠߊ࿾㔡ᕈߔߴࠅಽᏓߩᲧセᧄ⎇ⓥߩ㧞ߟߩࡕ࠺࡞(strong /weak coupling model)ߢౣ⃻ߐࠇߚᶏḴဳᏂᄢ࿾㔡ߩ࿾㔡ᕈߔߴࠅಽᏓߣ․ᓽߦߟ޿ߡ㧘ߘࠇߙࠇ࿑㧟ߣ⴫㧝ߦ␜ߔ㧚࿑ 㧟 ߩ strong
oupling model ߢߪ㧘ᥦ⦡ၞߦ߅޿
ߡ㧘ᶏᵗࡊ࡟࡯࠻ߣ㒽஥ࡊ࡟࡯࠻߇߶߷ቢోߦ࿕⌕ߒ㧘ᶏḴဳᏂᄢ࿾
㔡ߩ㓙ߦ㧘ᶏḴ߹
ߢ 2m એ਄ߩߔߴࠅ߇⓭߈ᛮߌߡ޿ࠆߎߣ߇ಽ߆ࠆ㧚৻ ᣇ ߢ

weakcoupling model ߢߪ㧘࿾㔡ᕈߔߴࠅ߇ᶏḴ߹ߢ⓭߈ᛮߌߥ޿ߚ߼㧘ᄢ߈ߥᵤᵄ߇⊒↢ߒߦߊ޿࿾㔡ߢ޽ࠅ㧘࿑㧟㧚(਄) strong (ਅ) weak coupling model ߦ߅ߌࠆ㧘࿾㔡ᕈߔߴࠅ (Dseis)

1944 ᐕߩ᧲ධᶏ࿾ߩⓨ㑆ಽᏓ࿑㧚ߎߎߢߪ㧘3cm/sec ࠃࠅ㜞ㅦߥߔߴࠅߣቯ⟵ߒߚ㧚ࡊ࡟

㔡 [3] ߣ⺞๺⊛ ߢ࡯࠻㑆ࠞ࠶ࡊ࡝ࡦࠣ₸ (Cseis) ߳ߩ឵▚ߪ㧘(࿾㔡ᕈߔߴࠅ㊂) / (㧝ࠨࠗࠢ޽ࠆ㧚࡞ߩ✚ߔߴࠅ㊂) ߆ࠄ▚಴ߒߚ㧚⴫㧝㧚strong/ weak coupling model ߢߩᶏḴဳᏂᄢ࿾㔡ߩᲧセ㧔̪࿑㧟ߩᵈ㉼ࠍෳᾖ㧚
㧕
‛ℂࡄ࡜ࡔ࠲࡯ / ࡕ࠺࡞ౣ᧪㑆㓒࡮ⷙᮨ
Dseis, Csseis ߩᦨᄢ୯㧔̪㧕⎕უၞ

strong coupling model

weak coupling model143 ᐕ㧧Mw8.3

113 ᐕ㧧Mw7.9

5.3m㧦93%

3.4m㧦74%ᶏḴ߹ߢ⓭߈ᛮߌࠆ

Ꮒᄢࠕࠬࡍ࡝࠹ࠖၞߩ৻ㇱ  
4㧠㧚ᶏḴဳᏂᄢ࿾㔡ࠨࠗࠢ࡞ߦ઻߁⿥ૐ๟ᵄ࿾㔡ߩ㐳ᦼᄌൻ㧠㧚ᶏḴဳᏂᄢ࿾㔡ࠨࠗࠢ࡞ߦ઻߁⿥ૐ๟ᵄ࿾㔡ߩ㐳ᦼᄌൻ࿑㧠ߦ㧘ᵻㇱ஥ߣᷓㇱ஥ߩዊࠕࠬࡍ࡝࠹ࠖᏪ (࿑㧞ࠍෳᾖ) ߦ߅ߌࠆߔߴࠅㅦᐲߩⓨ㑆ጁᱧࠍ␜ߔ㧚ᤨ㑆ゲ (ᮮゲ) ߦߟ޿ߡߪᶏḴဳᏂᄢ࿾㔡ߩ⊒↢ᤨೞࠍ㐿ᆎᤨೞߣߒߡ޿ࠆ㧚ߎߩ࿑ߢߪ㧘⿒޿⦡ࠍߒߚㇱಽ߇ࠁߞߊࠅ࿾㔡ߦ⋧ᒰߒ㧘⊒↢ᤨ㑆㑆㓒࡮વ᠞ㅦᐲ㧔㤛࡮ᯍ⦡ߩ௑߈߆ࠄ᳞߼ࠆ㧕ࠍⷞⷡ⊛ߦᝒ߃ࠆ੐߇ߢ߈ࠆ㧚ߎߎߢ㧘weak / strong coupling model ߢᲧߴࠆߣ㧘ᷓㇱ஥ߪਔ⠪ߦᄢ߈ߥᏅߪ⷗ࠄࠇߥ޿߇㧘Ꮒᄢ࿾㔡⊒↢⋥ᓟ (ᤨೞ߇ 0 ㄭㄝ) ߢߩᵻㇱ஥ߦᵈ⋡ߔࠆߣ㧘weak coupling model ߢߪ㗫⊒ߔࠆ᭽ሶ߇⸻ࠄࠇࠆ߇㧘ᷓㇱ஥ߢߪᥦ⦡♽ߩ⦡߇ోߊߥ޿㧚ߎࠇߪࠁߞߊࠅ࿾㔡ߩ㕒
Ⓩൻࠍᗧ๧ߒ㧘․ߦਛᄩઃㄭ (Strike~0) ߢߪߘߩ⛮⛯ᤨ㑆߇㐳ߊߥࠆ௑ะ߇ߺࠄࠇࠆ㧚࿑㧠㧚Ꮐ߇ weak coupling model㧘ฝ߇ strong coupling model㧘਄߇ᵻㇱ㧘ਅ߇ᷓㇱߩዊࠕࠬࡍ࡝࠹ࠖᏪ (࿑㧞) ߢߩߔߴࠅㅦᐲߩⓨ㑆ጁᱧࠍ␜ߔ㧚⿒⦡߇ࠁߞߊࠅ࿾㔡㧘㕍⦡߇࿕⌕ߦ⋧ᒰߔࠆ㧚ᮮゲߩᤨ㑆ߪ㧘ᶏḴဳᏂᄢ࿾㔡ߩ⊒↢ᤨೞࠍේὐߣߒ㧘❑ゲߩේὐߪ࿑㧞ߣห᭽ߦᏂᄢࠕࠬࡍ࡝࠹ࠖߩਛᄩߦ૏⟎ߔࠆ㧚 ᧄⓂߢߪ㧘weak / strong coupling model ߩ㧞ߟࠍ଀ߣߒߡ␜ߒߚ߇㧘ઁߦ߽ᄙᢙߩᢙ୯ࠪࡒࡘ࡟࡯࡚ࠪࡦࠍ⹜ⴕߒߚ⚿ᨐ㧘Ꮒᄢࠕࠬࡍ࡝࠹ࠖౝߩ៺ᡂਇ቟ቯᕈ߇ᄢ߈޿߶ߤ㧘㕒Ⓩൻߩᦼ㑆߇㐳ߊ㧘㗔ၞ߇ᐢߊߥࠆ௑ะ߇ߺࠄࠇߚ㧚 
!"#$%&'()*+5㧡㧚߹ߣ߼ 㧠㧚ߩ⚿ᨐߦၮߠ޿ߡ㧘᧲ർᴒ๟ㄝߢߩ⿥ૐ๟ᵄ࿾㔡ߩᵴേߣࡊ࡟࡯࠻㑆࿕⌕ߣߩ㑐ଥࠍ࿑㧡ߦ߹ߣ߼ߚ㧚 ᧲ർ࿾ᣇᄥᐔᵗᴒ࿾㔡⊒↢ᓟߦ߅޿ߡ㧘ࠁߞߊࠅ࿾㔡ߩ৻⒳ߢ޽ࠆ⿥ૐ๟ᵄ࿾㔡ߩᵴേߦߟ޿ߡ㧘ችၔᴒߢߪ㕒Ⓩൻ߇ߺࠄࠇ㧘⑔ፉ࡮⨙ၔ࡮ጤᚻᴒߢߪᵴ
⊒ൻߒߚ [6]㧚 ߎߩ⚿ᨐࠍ࿑㧠ߦᒰߡߪ߼ࠆߣ㧘ችၔᴒઃㄭߢߪࡊ࡟࡯࠻㑆࿕⌕߇㕖Ᏹߦᒝߊ㧘⑔ፉ࡮⨙ၔ࡮ጤᚻᴒߢߪ㧘ࡊ࡟࡯࠻㑆࿕⌕߇ችၔᴒߦᲧߴߡᒙ޿㧘ᄖ✼ㇱߦ⋧ᒰߔࠆߣ⠨߃ࠄࠇࠆ㧚 ߹ߚ㧘੹ᓟߩ᷹ⷰ߆ࠄ᣿ࠄ߆ߦߐࠇࠆችၔᴒߢߩ㕒Ⓩൻߩ⛮⛯ᦼ㑆߿㧘ߘߩ㗔ၞߩᐢ߇ࠅ߆࿑㧡㧚2011 ᐕ 3 ᦬ 11 ᣣߩ᧲ർ࿾ᣇᄥᐔᵗᴒ࿾㔡ߩ࿾㔡ࠄ㧘᧲ർ࿾ᣇᄥᐔᵗᴒ࿾㔡ߢᏂᤨߔߴࠅಽᏓ [7] ߦ㧘2011 ᐕ 6 ᦬ 1 ᣣ㨪11 ᦬ 1 ᣣߢ⏕⹺ᄢߔߴࠅࠍ⊒↢ߐߖߚ㗔ၞߦߟߐࠇߚ⿥ૐ๟ᵄ࿾㔡 (VLF event) ߩ㔡ᄩಽᏓ(⿒ਣ) [8]㧘޿ߡ㧘ࡊ࡟࡯࠻㑆࿕⌕߇ߤࠇ߶࿾㔡ᵴേߩᷓㇱႺ⇇✢ (᩶⦡✢) [9 Igarashi]㧘ᧄ⎇ⓥߩᢙߤᒝ㕢ߥߩ߆ࠍផቯߔࠆᚻដ߆୯ࠪࡒࡘ࡟࡯࡚ࠪࡦ⚿ᨐߦၮߠߊ⸃㉼ (㐳ᣇᒻߩὐ✢㗔ࠅߣߥࠈ߁㧚ၞ) ࠍ㊀ߨߚ߽ߩ㧚 એ਄ࠃࠅ㧘ᵻㇱ⿥ૐ๟ᵄ࿾㔡ߩᵴേࠍ⋙ⷞߔࠆߎߣߢ㧘ࡊ࡟࡯࠻㑆࿕⌕ߩᤨ㑆ᄌൻࠍㅊ߁ߣ޿߁ᣂߚߥࠕࡊࡠ࡯࠴ࠍ㧘ᧄ⎇ⓥߩᢙ୯ࠪࡒࡘ࡟࡯࡚ࠪࡦ߆ࠄ⷗಴ߔߎߣ߇ߢ߈ߚ㧚⻢ㄉ ᧄ⎇ⓥߢߪ㧘᧲ർᄢቇࠨࠗࡃ࡯ࠨࠗࠛࡦࠬ࠮ࡦ࠲࡯ߣߩ౒ห⎇ⓥߦࠃߞߡ㐿⊒ߐࠇߚ㧘
SX-9 ะߌߦᦨㆡൻߐࠇߚ FFT ߩ⸘▚ࡊࡠࠣ࡜ࡓࠦ࡯࠼ࠍ૶↪ߒߚ㧚ߎࠇߦࠃࠅ㧘೨࿁ߩࡕ࠺࡞ࠃࠅ߽ᶏḴઃㄭߢߩ⸘▚ࡔ࠶ࠪࡘࠍ⚦ಽൻߒ㧘120 ਁ୘߽ߩ⸘▚ࡔ࠶ࠪࡘࠍ᦭ߔࠆᄢⷙᮨࠪࡒࡘ࡟࡯࡚ࠪࡦࠍታᣉߔࠆߎߣ߇น⢻ߣߥࠅ㧘⸃௝ᐲߩ㜞޿ㅪ⛯⊛ߥߔߴࠅㆊ⒟ࠍౣ⃻ߔࠆߎߣ߇ߢ߈ߚ㧚 6ෳ⠨ᢥ₂[1] Ide, S., G. C. Beroza, D. R. Shelly, and T. Uchide, 2007. A scaling law for slow earthquakes,
Nature 447, 76-79, doi:10.1038/nature05780.
[2] Sugioka, H., T. Okamoto, T. Nakamura, Y. Ishihara, A. Ito, K. Obana, M. Kinoshita, K.
Nakahigashi, M. Shinohara, Y. Fukao, 2012. Tsunamigenic potential of the shallow

subduction plate boundary inferred from slow seismic slip, Nature Geoscience 5,414-418. doi:10.1038/NGEO1466.
[3] ᦭ศ ᘮ੺࡮᧻Ỉ ᥰ࡮ᣣ㊁ ੫ᄥ࡮㐳⼱Ꮉ ᤘ࡮ၳ 㜞ፄ࡮ਛ↰ ઎ሶ࡮㊄↰ ⟵ⴕ, 2011. ᶏḴઃㄭߢ⊒↢ߔࠆᵻㇱࠁߞߊࠅ࿾㔡ߩ․ᓽ, SENAC 44(4), 33-46.
[4] ࿖࿯࿾ℂ㒮, 2011, ᧲ർ࿾ᣇᄥᐔᵗᴒ࿾㔡ߩ㒽ၞ෸߮ᶏၞߩ࿾ᲖᄌേߣṖࠅಽᏓࡕ࠺࡞,http://www.gsi.go.jp/cais/topic110520-index.html.
[5] Ampuero, J.-P. and A. M. Rubin, Earthquake nucleation on rate and state faults – Aging and slip
laws, J. Geophys. Res. 113, B01302, doi:10.1029/2007JB005082.
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