東北地域災害科学研究37

第59巻（2023）

ୗ໭ ༙ ᓥ 㸪㛵 ᰿ ὾ ࡢ࢖ ࣋ ࣥ ࢺሁ ✚ ≀ ࡟ࡘ ࠸ ࡚ *ᘯ๓኱ Ꮫ⌮ ᕤᏛ 㒊  ᮌᮧ 㞝 ኱ᘯ๓኱ Ꮫ኱ Ꮫ㝔 ⌮ᕤ Ꮫ◊ ✲⛉  ᒸ⏣ 㔛 ዉᘯ๓኱ Ꮫ኱ Ꮫ㝔 ⌮ᕤ Ꮫ◊ ✲⛉  ᱵ⏣ ᾈ ྖ1㸬
㸬 ࡣࡌࡵ ࡟᪥ᮏᾏ⁁࣭༓ᓥᾏ⁁ἢ࠸ࡢ㡿ᇦ࡛ࡣ㸪ᕧ኱࡞ᆅ㟈ࡀ⧞ࡾ㏉ࡋⓎ⏕ࡋ࡚࠾ࡾ㸪㐣ཤ࡟ከࡃࡢ⿕ᐖࢆཷࡅ࡚ࡁࡓࠋ2011 ᖺᮾ໭ᆅ᪉ኴᖹὒἈᆅ㟈௨㝆㸪ὠἼሁ✚≀ࡢㄪᰝࡀ┒ࢇ࡟⾜ࢃࢀ㸪ࡇࢀࡲ࡛ሗ࿌ࡀ࡞࠿ࡗࡓ໭ᾏ㐨ࡢ⫹᣺ᆅ᪉㸦㧗ΎỈ࡯࠿㸪2013㸧ࡸୗ໭༙ᓥࡢኴᖹὒഃ࡟ 17 ୡ⣖࡟Ⓨ⏕ࡋࡓ࡜⪃࠼ࡽࢀࡿᆅ㟈࡟క࠺ὠἼሁ✚≀ࡀぢࡘ࠿ࡗࡓ㸦Tanigawa et al., 2014㸧ࠋࡇࢀࡽࡢὠ
Ἴሁ✚≀ࡢศᕸࢆㄝ᫂ࡍࡿࡓࡵ࡟ࡣ㸪1611 ᖺࡢ៞㛗୕㝣ᆅ㟈ࡢ㟈※ᇦࢆᚑ᮶ࡼࡾࡶ໭ഃ࡟᝿ᐃ
ࡍࡿࡇ࡜ࡸ㸪17 ୡ⣖ࡢ໭ᾏ㐨ᮾ㒊ࡢᆅ㟈ࡢ㟈※ᇦࢆすഃࡲ࡛ᗈࡆࡿ࡜࠸ࡗࡓ᝿ᐃࡀᚲせ࡜࡞ࡿࠋ௨ୖࡢࡇ࡜࠿ࡽ㸪㟷᳃┴࡛ࡣ≉࡟ୗ໭༙ᓥ࡛ࡢὠἼሁ✚≀ࡢㄪᰝࡀ㔜せ࡜࡞ࡿࠋ᭱㏆࡟࡞ࡗ࡚➹⪅ࡽࡢࢢ࣮ࣝࣉࡣ㸪ୗ໭༙ᓥ໭㒊ࡢ㛵᰿὾࡟࠾࠸࡚」ᩘᯛࡢ࢖࣋ࣥࢺሁ✚≀ࢆᣳࡴ㟢㢌ࢆⓎぢࡋࡓࠋࡑࡇ࡛ࡣᒙ┦ほᐹ࣭グ㍕ࢆ⾜࠺࡜࡜ࡶ࡟㸪ᐊෆ࡛ࡣ X ⥺ CT ᧜ᙳ㸪㖔≀⤌ᡂ㸦࣮ࣔࢻศᯒ㸧㸪⢏ᗘศᯒ㸪14C ᖺ௦ᐃ㸪⌛⸴ศᯒ࡞࡝ࢆ⾜ࡗࡓࡢ࡛㸪ࡑࢀࡽࡢ⤖ᯝ࡟ࡘ࠸࡚ሗ࿌ࡍࡿࠋ

2㸬㸬 ㄪᰝᆅ Ⅼ࠾ ࡼࡧ ㄪᰝ ᪉ἲㄪᰝᆅⅬࡣ㸪ୗ໭༙ᓥ໭➃ࡢ㛵᰿὾ࡢᮾഃ࡟఩⨨ࡍࡿࠋ㟢㢌ࡣᾏᓊ࠿ࡽ⣙ 50㹫㞳ABࢀࡓ㸪᭱⤊㛫ịᮇࡢᾏᡂẁୣ࡜ᾏᓊ⥺ࡢ㛫ࡢᶆ㧗⣙ 5m ࡢᚤ㧗ᆅ࡛࠶ࡾ㸪ࡑࡢᶆ㧗ࡣ⣙ 1.5㹫࡛࠶ࡿ㸦ᅗ-1㸧ࠋ࢖࣋ࣥࢺሁ✚≀ࡢ≉ᚩࢆ᫂ࡽ࠿࡟ࡍࡿࡓࡵ㸪ᒙ┦ほᐹ࣭グ㍕
࠾ࡼࡧヨᩱ᥇ྲྀࢆ⾜ࡗࡓࠋ᥇ྲྀࡋࡓヨᩱCࡣ㸪250mm×65mm×10mm ࡛ཌࡉ 1mm ࡢ࢔ࢡࣜࣝᐜჾ࡟ᑒධࡋ㸪 X ⥺ CT ⏬ീ᧜ᙳࢆ⾜ࡗࡓ㸬᧜ᙳࡣ㧗▱ࢥ࢔ࢭࣥࢱ࣮ࡢ X ⥺CT ࢫ࢟ࣕࢼ Aquilion PRIME Focus Edition㸦࢟ࣖࣀ࣓ࣥࢹ࢕࢝ࣝࢩࢫࢸ࣒ࢬ〇㸧ࢆ౑⏝ࡋࡓࠋ࡞࠾㸪ᐇ㉁ⓗ࡞✵㛫ศゎ⬟ࡣ⣙
1mm ࡛࠶ࡿࠋࡲࡓ㸪᥇ྲྀࡋࡓヨᩱࡢ୍㒊ࡣ㸪ᅗ-1 ㄪᰝᆅⅬࡢ఩⨨ᅗA㸸ୗ໭༙ᓥ㸪㹀㸸㛵᰿὾࿘㎶㸪㹁㸸㟢㢌఩⨨㉸㡢ἼὙίᶵ࡟ࡼࡗ࡚Ἶᡂศࢆ㝖ཤࡋࡓࡢࡕ㸪1/4mm㹼1/16mm ࡟⠠ศࡅࢆ⾜࠸㸪⣙ 200 ⢏Ꮚࢆ┠㏵࡟ᐇయ㢧ᚤ㙾ࢆ⏝࠸࡚▼ⱥ㸪ᩳ㛗▼㸪ゅ㛝▼㸪㍤▼㸪☢㕲㖔㸪▼㉁ᒾ∦࡟༊ศࡋ㸪ࡑࡢ๭ྜࢆồࡵࡓࠋ⢏ᗘศᯒࡣ࣮ࣞࢨ࣮ᅇᯒ⢏ᗘศᕸᐃ⿦⨨ SALD-3000J㸦ᓥὠ〇సᡤ〇㸧ࢆ⏝࠸࡚ 0.1㹼2000 ੇࡢศᯒ⠊ᅖ࡛⾜ࡗࡓࠋᨺᑕᛶ

*Characteristics of event deposits in Sekine-hama, Shimokita peninsula by Yuta Kimura, Rina Okada and KojiUmeda

38Ⅳ⣲ᖺ௦

ᐃࡣ᪥ᮏཎᏊຊ◊✲㛤Ⓨᶵᵓᮾ⃰ᆅ⛉Ꮫࢭࣥࢱ࣮ࡢຍ㏿ჾ㉁㔞ศᯒ⿦⨨ࢆ⏝࠸ࡓࠋ⌛⸴ࡣගᏛ㢧ᚤ㙾㸦400 㹼 1000 ಸ㸧࡛ほᐹࡋ㸪100㹼250 ಶࡢ⌛⸴໬▼ࡢ᳨ᐃ࣭ィᩘࢆ⾜ࡗࡓࠋ3㸬㸬 ᒙ┦ほ ᐹ௒ᅇ㸪ほᐹࡋࡓ㟢㢌ࡣ㸪ୖ఩ࡀ◁ΰࡌࡾࡢ᭷ᶵ㉁ࢩࣝࢺᒙ㸪ୗ఩
ࡀἾⅣࢆ୺య࡜ࡋ㸪ࡑࡇ࡟ࡣ࢖࣋
ࣥࢺሁ✚≀࡜⪃࠼ࡽࢀࡿ 8 ᒙࡢ◁ᒙࡀᣳࡲࢀ࡚࠸ࡿ㸦ᅗ-2㸧ࠋᆅ⾲࠿ࡽ῝ᗘ 0.10m ࡲ࡛ࡣᴟ⣽⢏◁ࡢ㢼ᡂᒙ࠿ࡽ࡞ࡿࠋ῝ᗘ 0.10㹼
0.32㹫ࡣ⣽㹼୰⢏◁࡛࢖࣋ࣥࢺ Hᒙ࡜࿨ྡࡋࡓࠋ῝ᗘ 0.32㹼0.38㹫
ࡣ᭷ᶵ㉁ࢩࣝࢺ࠿ࡽ࡞ࡿࠋ῝ᗘ
0.38 㹼 0.41 㹫 ࡣ Ἶ ΰ ࡌ ࡾ ⣽ ⢏ ◁㸦G ᒙ㸧㸪῝ᗘ 0.41㹼0.42m ࡣ᭷
ᶵ㉁ࢩࣝࢺᒙࢆᣳࡴࠋࡑࡢୗ఩ࡢ
῝ᗘ 0.42㹼0.56㹫ࡣ⣽㹼୰⢏◁㸦Fᒙ㸧࡛㸪ୖ᪉⣽⢏໬ࡀㄆࡵࡽࢀࡿࠋ
ࡲࡓ㸪ୗ఩ࡢἾⅣᒙ㸦῝ᗘ 0.56㹼
0.65㹫㸧࡜ࡢቃ⏺ࡣ᫂░࡞౵㣗㠃ࡀㄆࡵࡽࢀࡿࠋ
῝ᗘ 0.65㹼0.69m ࡣ⣽⢏◁㸦Eᒙ㸧㸪῝ᗘ 0.69㹼0.74m ࡣἾⅣᒙ㸪῝ᗘ 0.74㹼0.77m ࡣῐ㯤〓Ⰽࡢ⣽⢏ ⅆ ᒣ ⅊㸦D ᒙ 㸧㸪 ῝ ᗘ 0.77㹼
0.86m ࡣἾⅣ㸪῝ᗘ 0.86㹼0.90㹫ࡣἾⅣΰࡌࡾ⣽⢏◁㸦C ᒙ㸧㸪῝ᗘ
0.90㹼1.15m ࡣἾⅣ㸪῝ᗘ 1.15㹼
1.19m ࡣ⣽⢏◁㸦B ᒙ㸧㸪῝ᗘ 1.19
㹼1.32m ࡣἾⅣ࡛㸪኱ᆺࡢᮌ∦ࡀ

ᅗ-2 ࢖࣋ࣥࢺሁ✚≀㸦ᢡᑻࡢ㛗ࡉ㸦ୖୗ㸧ࡣ 75cm㸧
ձ㹼մࡣ 14C ᖺ௦ヨᩱ᥇ྲྀ఩⨨ྵࡲࢀࡿࠋ῝ᗘ 1.32㹼1.34m ࡣ⣽⢏◁㸦A ᒙ㸧࡛㸪῝ᗘ 1.34㹼1.54m ࡣἾⅣ࠿ࡽ࡞ࡿࠋ4㸬㸬 㖔≀⤌ ᡂ࣭ ⢏ᗘ ศᯒ࢖࣋ࣥࢺ A㹼C ࠾ࡼࡧ E㹼G ࡣ࡜ࡶ࡟୰㹼⣽⢏◁ࢧ࢖ࢬࡢ◁ᒙ࡛࠶ࡾ㸪㖔≀⤌ᡂ㸪⢏ᗘศᕸ࡜ࡶ࡟㸪ᾏ὾◁࡜㢮ఝࡍࡿࠋᅗ-3 ࡟ᾏ὾◁࡜࢖࣋ࣥࢺ E ࡢᐇయ㢧ᚤ㙾෗┿㸪⢏ᗘศᕸ㸪㖔≀໬Ꮫ⤌ᡂࢆ♧ࡍࠋࡇࡢ㟢㢌࡛ࡳࡽࢀࡿ◁ᒙ㸦࢖࣋ࣥࢺሁ✚≀㸧ࡣ㸪࠸ࡎࡶᾏ὾◁ࡀ㐠ᦙ࣭ሁ✚ࡋࡓࡶࡢ࡛࠶ࡾ㸪ᾏ⏤᮶ࡢ࢖࣋ࣥࢺ㸦ὠἼ㸪㧗₻➼㸧࡟ࡼࡗ࡚ᙧᡂࡉࢀࡓ࡜⪃࠼ࡽࢀࡿࠋ࡞࠾㸪39࢖࣋ࣥࢺ D ࡜ࡋࡓῐ㯤〓Ⰽࡢ⣽⢏ⅆᒣ⅊ࡣ㸪೫ග㢧ᚤ㙾ほᐹ࡟ࡼࡿ࡜ࣂࣈ࢛࣮ࣝ࢘ࣝᆺࡢⅆᒣ࢞ࣛࢫ࠿ࡽᵓᡂࡉࢀࡿࡇ࡜㸪࢚ࢪ࣮ࣜࣥ࢜ࢪࣕ࢖ࢺࢆྵࡴࡇ࡜࠿ࡽすᬺ 946 ᖺ㸦Oppenheimer etal., 2017㸧࡟㝆⅊ࡋࡓⓑ㢌ᒣ࣭Ɫᑠ∾ࢸࣇࣛ㸦B-Tm㸧࡜⪃࠼ࡽࢀࡿࠋࡲࡓ㸪࢖࣋ࣥࢺ H ࡣ㸪○ᒌ⢏Ꮚࡀ࡯࡜ࢇ࡝෇ᦶࡉࢀ࡚࠸࡞࠸ࡇ࡜㸪㍤▼ࡢྵ᭷㔞ࡀ኱ࡁ࠸ࡇ࡜࡞࡝࠿ࡽ㝣⏤᮶ࡢ࢖࣋ࣥࢺ㸦౛࠼ࡤ㸪ὥỈ㸧࡟ࡼࡿሁ✚≀ࡢྍ⬟ᛶࡀ࠶ࡿࠋ

ܱ˳᫋ࣇᦟϙჇίොჿὸ

ቩࡇЎࠋίොჿὸ

ᤸཋኵ঺ίොჿὸ

ܱ˳᫋ࣇᦟϙჇίỶἫὅἚFὸቩࡇЎࠋίỶἫὅἚFὸ

ᤸཋኵ঺ίỶἫὅἚFὸ

ᅗ-3 ᾏ὾◁㸦ୖẁ㸧࡜࢖࣋ࣥࢺ F㸦ୗẁ㸧ࡢᐇయ㢧ᚤ㙾෗┿㸪⢏ᗘศᕸ㸪㖔≀໬Ꮫ⤌ᡂ5㸬
㸬 14C ᖺ ௦ᐃ

ᅗ-2 ࡢձ㹼մࡢἾⅣࡢ 14 C ᖺ௦ࢆ⾲-1 ࡟♧ࡍࠋ࢖࣋ࣥࢺ A ࡣ

⾲-114C ᖺ௦ᐃ⤖ᯝ

3850㹼2750 ᖺ๓㡭㸪࢖࣋ࣥࢺ B ࡣ 2850㹼2100 ᖺ๓㡭㸪࢖࣋ࣥࢺ C ࡣ 2200 ᖺ๓㡭㹼すᬺ 946 ᖺ㸪࢖࣋ࣥࢺ E ࡣすᬺ 946 ᖺ๓
㹼17 ୡ⣖࡟ᾏ⏤᮶ࡢ࢖࣋ࣥࢺ࡟ࡼࡗ࡚ᙧᡂࡉࢀࡓሁ✚≀࡛࠶ࡿ࡜⪃࠼ࡽࢀࡿࠋࡲࡓ㸪࢖࣋ࣥࢺ F㹼H ࡣ㸪17 ୡ⣖௨㝆࡟ሁ✚ࡋࡓ࢖࣋ࣥࢺ࡜⪃࠼ࡽࢀࡿࠋ
6㸬㸬 ㆟ㄽ
ࡇࢀࡽࡢ⤖ᯝ࠿ࡽ㸪࢖࣋ࣥࢺ F ࠾ࡼࡧ G ࡣ㸪17 ୡ⣖௨㝆࡟ᾏ⏤᮶ࡢ࢖࣋ࣥࢺ࡟ࡼࡗ࡚ᙧᡂࡉࢀࡓሁ✚≀ࡢྍ⬟ᛶࡀ㧗࠸ࠋ௨ୗࡢ㆟ㄽ࡛ࡣ࢖࣋ࣥࢺ F ࡜ G ࢆేࡏ࡚ Em1 ࡜࿧ࡪࠋ๓㏙ࡋࡓࡼ࠺࡟㸪Em1 ࡜ୗ఩ࡢἾⅣࡢቃ⏺ࡣ᫂░࡞౵㣗㠃ࡀㄆࡵࡽࢀࡿࡇ࡜㸪Ἶ㉁ᡂศ࡟ᐩࡴⷧᒙ㸦࣐ࢵࢻࢻࣞ࢖ࣉ?㸧ࡀᣳࡲࢀࡿࠋᅗ-4 ࡟ Em1 ࡢ X ⥺ CT ⏬ീࢆ♧ࡍࠋ㟢㢌࡛ࡣࢃ࠿ࡾ࡟ࡃ࠸ࡀ X⥺ CT ෗┿࡛ࡣᖹ⾜㹼ᩳ஺ⴥ⌮ࡀㄆࡵࡽࢀࡿࡇ࡜࠿ࡽ㸪○ᒌ⢏Ꮚࡣᙉ࠸Ỉὶ࡟ࡼࡗ࡚㐠ࡤࢀࡓ40ࡢࡕ㸪ࡑࡢὶࢀࡀ೵⁫ࡋࡓࡇ࡜ࡀ♧၀ࡉࢀࡿ㸬ࠋEm1 ࠾ࡼࡧࡑࡢୗ఩ࡢἾⅣᒙࡢ⌛⸴ศᯒࡢ⤖ᯝࢆࡳࡿ࡜㸪ୗ఩
ࡢἾⅣᒙ࡟ࡣῐỈᛶࡢ⌛⸴ࡋ࠿ㄆࡵࡽࢀ࡞࠸ࡢ࡟ᑐࡋ
࡚ 㸪 Em1 ࡟ ࡣ Ỷ Ỉ ᛶ ࡢ Diploneis smithii ࡸ Diploneis
interrupta㸪Cocconeis stauroneiformis ࡞࡝ࡢᾏỈᛶ㹼ỶỈᛶ ࡢ ⌛ ⸴ ࡀ 40%⛬ ᗘ ྵ ࡲ ࢀ ࡚ ࠸ ࡿ ࠋ ≉ ࡟ 㸪 Cocconeis
stauroneiformis ࡣᾏ⏕⏕≀࡟௜╔ࡋ࡞ࡀࡽ⏕ᜥࡋ࡚࠸ࡿࡶࡢ࡛㸪ᙉ࠸ᾏὶ࡟ࡼࡗ࡚㐠ࡤࢀࡓࡇ࡜ࡣ㛫㐪࠸࡞࠸ࠋ௨ୖࡢࡇ࡜࠿ࡽ㸪௒ᅇⓎぢࡉࢀࡓ㛵᰿὾ࡢ࢖࣋ࣥࢺሁ✚≀ Em1 ࡣ㸪Tanigawa et al.㸦2014㸧ࡀሗ࿌ࡋࡓୗ໭༙ᓥᮾ

E m1㏻ᮧࡢὠἼሁ✚≀ S1 ࡜ᑐẚ࡛ࡁࡿྍ⬟ᛶࡀ࠶ࡿࠋ
ᅗ-4 Em1㸦F㹼G ᒙ㸧ࡢ X ⥺ CTᘬ⏝ᩥ ⊩㧘ΎỈᗣ༤࣭Ọ஭ ₶࣭ᒸᮧ ⪽࣭すᮧ⿱୍㸦2013㸧 ◁ୣࢆ㉺࠼࡚ἢᓊపᆅࢆ㐳ୖࡋࡓὠἼ࡟ࡼࡿሁ✚ࣔࢹࣝ㸸໭ᾏ㐨⫹᣺ᾏᓊᮾ㒊࡟ศᕸࡍࡿ 17 ୡ⣖ὠἼሁ✚≀ࡢ◊✲౛. ᆅ㉁㞧㸪119,1–16㸬
Tanigawa K., Sawai, Y., Shishikura, M., Namegaya, Y. and Matsumoto, D., 2014, Geological evidence
for an unusually large tsunami on the Pacific coast of Aomori, northern Japan. Jour. Quatern. Sci.,
29, 200–208.