㸰㸮㸯㸷ᖺ すஅᓥ࡟࠾ࡅࡿᆅ㟈࣭✵᣺ほ ኱‖㝯㞝  ࠊΏ㑓⠜ᚿ 

Seismic and Infrasound observation at Nishinoshima Island in 2019
Takao OHMINATO1* & Atsushi WATANABE11. ᮾி኱Ꮫᆅ㟈◊✲ᡤ㸦ࠛ113-0032 ᮾி㒔ᩥி༊ᘺ⏕ 1-1-1㸧
Earthquake Research Institute, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-0032, Japan.
* takao@eri.u-tokyo.ac.jp (author for correspondence)せ᪨ すஅᓥࡢⅆᒣάືࢆࣔࢽࢱࣜࣥࢢࡍࡿࡇ࡜ࢆ┠ⓗ࡜ࡋ࡚ࠊ2019 ᖺ 9 ᭶ 3 ᪥㹼4 ᪥࡟すஅᓥࡢᪧᓥ㒊ศ࡟ᆅ㟈ィ࡜✵᣺ィࢆタ⨨ࡋࡓࠋほ ⿦⨨ࡣࠊᆅ㟈ィࠊ✵᣺ィࠊࢹ࣮ࢱ࣮ࣟ࢞ࠊ⾨ᫍ㏻ಙࣔࢹ࣒ࠊኴ
㝧㟁ụࠊࣂࢵࢸ࣮ࣜ࠿ࡽ࡞ࡿࠋᆅ㟈࠾ࡼࡧ✵᣺ࢹ࣮ࢱࡣࢹ࣮ࢱ࣮࡛ࣟ࢞ࢹࢪࢱ࢖ࢬࡉࢀ࡚ෆⶶ࣓ࢹ࢕࢔࡟グ㘓ࡉࢀࡿࠋ࣮ࣟ࢞ෆ࡛ࡣᆅືࢹ࣮ࢱࡢࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝࢆィ⟬ࡋࠊᅽ⦰ࡋࡓ࠺࠼࡛⾨ᫍᅇ⥺ࢆ㏻ࡌ࡚ᮾி኱Ꮫᆅ㟈◊✲ᡤ࡟࠶ࡿࢧ࣮ࣂ࣮࡟㏦ಙࡍࡿࠋࡇࡢ௙⤌ࡳ࡟ࡼࡾࠊᖏᇦࡀ㝈ࡽࢀࡓ⾨ᫍᅇ⥺ࢆ౑⏝ࡋ࡞ࡀࡽࠊᆅ㟈άືࢆᢕᥱࡍࡿࡓࡵ࡟ᚲせ࡞ᆅືࡢ㐃⥆᝟ሗࢆᚓࡿࡇ࡜ࡀ࡛ࡁࡿࠋࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝୖ࡛ᄇⅆάືࡢ᭷↓ࢆุ᩿ࡋࠊᚲせ࡛࠶ࢀࡤᅽ⦰๓ࡢᆅ㟈࣭✵᣺Ἴᙧグ㘓ࢆ࣮ࣟ࢞࠿
ࡽ㏦ಙࡍࡿࡇ࡜ࡶྍ⬟࡛࠶ࡿࠋ ᪧᓥෆ࡟タ⨨ࡉࢀࡓほ ⿦⨨ࡣⅆᒣάື࡟㉳ᅉࡍࡿᆅືࡢࡳ࡞ࡽࡎࠊከᵝ࡞᣺ື※࠿ࡽࡢ᣺ືࢆ࡜ࡽ࠼࡚࠾ࡾᪧᓥෆࡢᵝࠎ࡞άືࢆ⌮ゎࡍࡿ࠺࠼࡛㔜せ࡞ᇶ♏ࢹ࣮ࢱࡀᚓࡽࢀࡘࡘ࠶ࡿࠋ2019 ᖺ 12 ᭶࡟ࡣすஅᓥࡢⅆᒣάືࡀ෌㛤ࡋࡓࡀࠊほ ⿦⨨ࡣⅆᒣάື࡟క࠺ᆅ㟈ࡸ✵᣺ࢆ࠸ࡕ᪩ࡃ࡜ࡽ࠼࡚࠾ࡾࠊすஅᓥࡸࡑࡢ࿘㎶࡟࠾ࡅࡿㄪᰝάືࡢᏳ඲⟶⌮࡟ࡶ㈨ࡍࡿࡇ࡜ࡀ♧ࡉࢀࡓࠋ࣮࣮࢟࣡ࢻ
 ⾨ᫍ㏻ಙࠊⅆᒣᛶᆅ㟈ࠊⅆᒣࡢࣔࢽࢱࣜࣥࢢ㸯㸬ࡣࡌࡵ࡟

− 53 − ᮏሗ࿌࡛ࡣࠕ2019 ᖺすஅᓥ⥲ྜᏛ⾡ㄪᰝ࡛ࠖᐇ᪋ࡉࢀࡓྛ✀ㄪᰝ㡯┠ࡢ࠺ࡕⅆᒣάືほ ࡢᴫせࢆ㏙࡭ࡿࠋᮏㄪᰝࡢ┠ⓗࡣᆅ㟈ཬࡧ✵᣺ࢆほ ࡍࡿࡇ࡜࡟ࡼࡾすஅᓥࡢⅆᒣάືࢆᢕᥱࡍࡿࡇ࡜࡛࠶ࡿࠋ ᑠ➟ཎㅖᓥࡢすஅᓥ࡛ࡣ 2013 ᖺ 11 ᭶࡟⁐ᒾὶฟࢆక࠺ⅆᒣάືࡀጞࡲࡾࠊ᪤Ꮡࡢすஅᓥ㸦௨ୗᪧᓥ࡜࿧ࡪ㸧ࡣ୍㒊ࢆ㝖ࡁ⁐ᒾὶ࡛ᇙࡵᑾࡃࡉࢀࡓࠋ୍㐃ࡢάືࡣ 2013 ᖺ-2015 ᖺࡢάື㸦➨ 1 ᮇ㸧ࠊ2017 ᖺࡢάື㸦➨ 2 ᮇ㸧ࠊ2018 ᖺࡢάື㸦➨ 3 ᮇ㸧࡟ศࡅࡽࢀࡿࠋ➨ 1 ᮇ࡜➨ 2 ᮇࡢ㛫ࡢᄇⅆάື೵Ṇᮇ㛫୰ࡢ 2016 ᖺ 10 ᭶࡟ᄇⅆ㛤ጞᚋึࡢୖ㝣ㄪᰝࡀ⾜ࢃࢀࠊᆅ㉁ㄪᰝ࣭ᄇฟ≀᥇ྲྀ࣭ᆅ㟈ィ࠾ࡼࡧ✵᣺ィࡢタ⨨࣭⏕≀ㄪᰝࡀᐇ᪋ࡉࢀࡓ㸦Ṋᑿ࡯࠿ࠊ2018㸪๓㔝࡯࠿ࠊ2018㸧ࠋᮏㄪᰝࡣ 2018 ᖺࡢάືᚋࡢ㟼✜࡞᫬ᮇࢆ㑅ࢇ࡛ᐇ᪋ࡋࡓ⥲ྜⓗ࡞ୖ㝣ㄪᰝ࡛࠶ࡾࠊᆅ㟈࣭✵᣺ほ ᶵჾࡢタ⨨ࡣ 2013 ᖺ࡟すஅᓥࡢ⌧ᅾࡢⅆᒣάືࡀጞࡲࡗ࡚௨᮶ 2 ᗘ┠࡜࡞ࡿࠋ 2016 ᖺ࡟タ⨨ࡋࡓᆅ㟈࣭✵᣺ィ࡟ࡼࡾᚓࡽࢀࡓ▱ぢࡣ௨ୗࡢᵝ࡟ࡲ࡜ࡵࡽࢀࡿࠋ2016 ᖺ 10 ᭶࡟タ⨨ࡋࡓᆅ㟈࣭✵᣺ほ ⿦⨨࡛ࡣタ⨨࠿ࡽ⣙༙ᖺᚋࡢ 2017 ᖺ 4 ᭶࡟ᄇⅆάືࡀ෌㛤ࡋࠊᄇⅆ㛤ጞ᫬ࡢ㔜せ࡞ࢹ࣮ࢱࡀᚓࡽࢀࡓࠋࡇࡢᄇⅆάືࡣ 4 ᭶ 17 ᪥ 11 ᫬㡭࠿ࡽప࿘Ἴࡀ༟㉺ࡍࡿ┦ఝᆅ㟈ࡢ⩌Ⓨάືࡀඛ⾜ࡋ࡚ጞࡲࡗࡓࠋ┦ఝᆅ㟈࡜ࡣ⧞ࡾ㏉ࡋ࡚Ⓨ⏕ࡍࡿἼᙧࡢⰋࡃఝࡓᆅ㟈࡛࠶ࡾࠊⅆᒣάື࡟కࡗ
࡚ࡋࡤࡋࡤほ ࡉࢀࡿࠋ⩣ 18 ᪥࡟ࡣ᣺ᖜࡢ኱ࡁ࡞ᆅ㟈ࡀⓎ⏕ࡋ┦ఝᆅ㟈ࡢ㢖ᗘࡶ㧗ࡲࡗࡓࠋ18 ᪥ 8᫬࡟ࡣᄇⅆࡢ㛤ጞࢆ♧ࡍ✵᣺ࡀⓎ⏕ࡋࠊⅆᒣᛶᚤືࡀ࡯ࡰ㐃⥆ࡋ࡚Ⓨ⏕ࡍࡿ≧ែ࡟⛣⾜ࡋࡓࠋ⯟✵ᶵ࡟ࡼࡿ┠どほ ࡟ࡼࡗ࡚ᄇⅆάືࡢ㛤ጞ࡜⁐ᒾὶฟࡀ☜ㄆࡉࢀࡓࡢࡣ 4 ᭶ 20 ᪥࡟࡞ࡗ࡚࠿ࡽ࡛࠶ࡾࠊᆅ㟈࣭✵᣺ほ ࡣࡑࢀࡼࡾࡶ᪩ࡃᄇⅆάືࡢ෌㛤ࢆᤊ࠼࡚࠸ࡓࡇ࡜࡟࡞ࡿࠋほ Ⅼࡣ 4 ᭶ 21 ᪥࡟⁐ᒾὶ࡟ᇙࡶࢀ࡚㏻ಙࡀ㏵⤯࠼ࡓࡀࠊタ⨨࠿ࡽ࡯ࡰ༙ᖺ㛫࡟Ώࡾࠊ⥅⥆ⓗ࡟すஅᓥⅆᒣࡢᆅ㟈࣭✵᣺άືࢆࣔࢽࢱࣜࣥࢢࡍࡿࡇ࡜ࡀ࡛ࡁࡓࠋࡇࡢほ ࡟㛵ࡋ࡚ࡣࠊᶵჾタ⨨ࡢヲ⣽࡟ࡘ࠸࡚ࡣΏ㑓࡯࠿㸦2017㸧ࢆࠊほ ࢹ࣮ࢱࡢゎᯒ࡟ࡘ࠸࡚ࡣṊᑿ࡯࠿㸦2018㸧ࢆࠊࡑࢀࡒࢀཧ↷ࡉࢀࡓ࠸ࠋ すஅᓥࡣ 2019 ᖺ 12 ᭶࡟ᄇⅆࡀ෌㛤ࡋࠊᮏ✏ᇳ➹᫬Ⅼࡢ 2020 ᖺ 1 ᭶᫬Ⅼ࡛ࡶάືࡀ⥅⥆ࡋ࡚࠾ࡾࠊタ⨨ࡋࡓほ ᶵჾ࡟ࡼࡾᆅ㟈࣭✵᣺グ㘓ࡀᚓࡽࢀࡘࡘ࠶ࡿࠋᮏ✏࡛ࡣ⣬㠃ࡀ㝈ࡽࢀ࡚࠸ࡿࡇ࡜࠿ࡽࠊタ⨨ᶵᮦࡢヲ⣽ࡸタ⨨᪉ἲ࡞࡝ほ ᡭἲ࡟㛵ࡍࡿグ㍕ࢆ୺࡜ࡋࠊほ ࡛ᚓࡽࢀࡓࢹ࣮ࢱࡢ⤂௓ࡣ୍㒊࡟࡜࡝ࡵࡿࠋ෌㛤ࡋࡓⅆᒣάື࡟క࠺ᆅ㟈࣭✵᣺グ㘓ࡢヲ⣽࡞ゎᯒ࡟ࡘ࠸࡚ࡣ௚ㄅ࡟ㆡࡿࠋ㸰㸬ほ 㸰㸫㸯㸬ほ ࠾ࡼࡧࢹ࣮ࢱ㏻ಙࡢᴫせ ᅗ 1 ࡟ 2019 ᖺ 9 ᭶ࡢほ ⿦⨨タ⨨఩⨨ࢆ♧ࡍࠋẚ㍑ࡢࡓࡵࠊ2016 ᖺ 10 ᭶࡟タ⨨ࡋ 2017 ᖺ 4 ᭶ࡢάື࡛ᇙἐࡋࡓᶵჾタ⨨ࡢ఩⨨ࡶ♧ࡍࠋ௒ᅇ 2019 ᖺ 9 ᭶ࡢほ ࡟࠾࠸࡚ࡶ 2016 ᖺ 10 ᭶ㄪᰝ᫬࡜࡯ࡰྠࡌᶵᮦ࡜ᡭἲ㸦Ώ㑓࡯࠿ࠊ2017㸧ࢆ⏝࠸࡚࠸ࡿࠋᆅ㟈ィࡣࣀ࢖ࢬపῶࡢࡓࡵᇙタࡍࡿᚲせࡀ࠶ࡾࠊࡑࡢࡓࡵタ⨨ሙᡤࡣᇙタ࡛ࡁࡿᅵተࡀሁ✚ࡋ࡚࠸ࡿᪧᓥ࡟㝈ࡽࢀࡿࠋ㟁ຊࡣኴ㝧㟁ụ࡛౪⤥ࡋࠊࢹ࣮
ࢱࡢ㏦ಙࡣ⾨ᫍ㏻ಙࢆ⏝࠸࡚⾜࠺ࠋᆅ㟈࣭✵᣺ࡢࢹ࣮ࢱ㔞ࡣ 1 ᪥ᙜࡓࡾ⣙ 80MB ࡟㐩ࡍࡿࡓࡵࠊ඲࡚
ࡢࢹ࣮ࢱࢆࣜ࢔ࣝࢱ࢖࣒࡛㏦ࡿࡇ࡜ࡣ㏻ಙ㈝⏝ࡸᾘ㈝㟁ຊࡢไ㝈࡟ࡼࡾ㞴ࡋ࠸ࠋࡑࡢࡓࡵࠊࢹ࣮ࢱࢆప࿘Ἴഃ࡜㧗࿘Ἴഃ࡟ศࡅ࡚ࡑࢀࡒࢀ 1 ᪥ศࡢࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝࢆసᡂࡋࠊࡑࡢᅽ⦰ࣇ࢓࢖ࣝࡢࡳࢆᮾி኱Ꮫᆅ㟈◊✲ᡤࡢࢧ࣮ࣂ࣮࡟㏦ࡿࡇ࡜࡜ࡋࡓࠋࡇࢀ࡟ࡼࡾ㏦ಙࡍࡿࢹ࣮ࢱ㔞ࡣ 1 ᪥ᙜࡓࡾ500kB ⛬ᗘ࡟ῶࡽࡍࡇ࡜ࡀ࡛ࡁࡿࠋࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝࡣẖ᪥సᡂࡋ㏦ಙࡍࡿࡢ࡛ࠊᆅ㟈࣭✵᣺άືࡢᴫせࢆ⩣᪥࡟ࡣᢕᥱࡍࡿࡇ࡜ࡀ࡛ࡁࡿࠋࡲࡓᅽ⦰๓ࡢඖࡢἼᙧࢹ࣮ࢱࢆ⾨ᫍᅇ⥺⤒⏤࡛ᅇ཰ࡍࡿࡇ࡜ࡶ࡛ࡁࡿࠋࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝୖ࡛㢧ⴭ࡞࢖࣋ࣥࢺࡀぢࡘ࠿ࡗࡓሙྜࡣᑐᛂࡍࡿඖἼᙧࢹ࣮ࢱ
− 54 −

ࢆᅇ཰ࡋ࡚㏻ᖖࡢᆅ㟈࣭✵᣺Ἴᙧゎᯒࢆ⾜࠺ࡇ࡜ࡶྍ⬟࡛࠶ࡿࠋ௨ୗࠊほ ᶵჾࡸ㏻ಙ᪉ᘧ࡟ࡘ࠸࡚
ヲࡋࡃㄝ᫂ࡍࡿࠋ
㸰㸫㸰㸬ほ ᶵᮦ
 ほ ᶵᮦࡣ  ᖺほ ࡟౑⏝ࡋࡓࡶࡢ࡜࡯ࡰྠᵝ࡛࠶ࡿࡀࠊᆅ㟈ィ࡟ࡘ࠸࡚ࡣ㐠ᦙࡸタ⨨సᴗࡢ㈇ᢸࢆపῶࡍࡿࡓࡵ๓ᅇࡼࡾࡶᑠᆺࡢᶵ✀࡟ኚ᭦ࡋࡓࠋࡲࡓࠊኴ㝧㟁ụ࡟ࡘ࠸࡚ࡣ㐠ᦙࢆᐜ᫆࡟ࡍࡿ
࡜࡜ࡶ࡟タ⨨᫬ࡢ⮬⏤ᗘࢆୖࡆࡿࡓࡵ࡟ : ࣃࢿࣝ  ᯛ࠿ࡽ : ࣃࢿࣝ  ᯛ࡟ኚ᭦ࡋࡓࠋᶵᮦ୍ぴࢆ⾲  ࡟ࠊྛᶵᮦࡢእほࢆᅗ  ࡟♧ࡍࠋすஅᓥ࡬ࡢୖ㝣ࡣ࢙࢘ࢵࢺࣛࣥࢹ࢕ࣥࢢ࡜࡞ࡿࡓࡵᶵᮦࡣࡍ
࡭࡚㜵Ỉࢣ࣮ࢫ࡟཰⣡ࡋࡓࠋࢹ࣮ࢱ࣮ࣟ࢞࡜ࣂࢵࢸ࣮ࣜࡣ୍ࡘࡢ㜵Ỉࢣ࣮ࢫ㸦࣌ࣜ࢝ࣥࢣ࣮ࢫ 3&ࠊ
/ ੉: ੉+ ੉㸧࡟ࡲ࡜ࡵࡓࠋࡲࡓࠊ⾨ᫍ㏻ಙ➃ᮎࡣタ⨨᫬࡟࢔ࣥࢸࢼ㠃ࢆ⾨ᫍ࡟ྥࡅࡿᚲせࡀ࠶ࡿࡓࡵࠊ⊂❧ࡋࡓูࡢ㜵Ỉࢣ࣮ࢫ㸦࣌ࣜ࢝ࣥࢣ࣮ࢫ 3&ࠊ / ੉: ੉+੉㸧࡟཰⣡ࡋࡓ㸦ᅗ 㸧ࠋୖ㝣ᚋࡢタ⨨సᴗࢆ▷᫬㛫࡛☜ᐇ࡟⾜࠺ࡓࡵࠊಙྕ⥺ࡸ㟁※࡞࡝ࡢ㓄⥺ࡣ඲࡚㜵Ỉࢥࢿࢡࢱ௜ࡁࡢࢣ࣮ࣈࣝ᥋⥆ࡢࡳ࡛῭ࡴࡼ࠺࡟஦๓࡟⏝ពࡋࡓࠋࢹ࣮ࢱ࣮ࣟ࢞ࡢฎ⌮⣔࡟ࡶᨵⰋࢆຍ࠼ࠊࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝࡢ⏬ീࣇ࢓࢖ࣝ㸦MSHJ ࣇ࢓࢖ࣝ㸧ࡢࡳࢆ㏦ಙࡍࡿ᪉ᘧ࠿ࡽࠊࣛࣥࢽ
ࣥࢢࢫ࣌ࢡࢺࣝࡢᩘ್ࢹ࣮ࢱࢆ㏦ಙࡋࠊ⏬ീࡣཷಙᚋ࡟ᆅ㟈◊✲ᡤࡢࢧ࣮ࣂ࣮ୖ࡛సᡂࡍࡿ᪉ᘧ࡟ኚ᭦ࡋࡓࠋࡇࢀ࡟ࡼࡾ࿘Ἴᩘ㡿ᇦ࡟࠾ࡅࡿᐃ㔞ⓗゎᯒࢆ⾜࠺ࡇ࡜ࡀྍ⬟࡟࡞ࡗ࡚࠸ࡿࠋ㸰㸫㸱㸬ࢹ࣮ࢱࡢ⵳✚࣭ฎ⌮࣭㏦ಙ
 ᮏほ ࡛⏝࠸ࡿࢹ࣮ࢱ࣮ࣟ࢞ࡣᆅ㟈Ἴᙧࡢୖୗࠊᮾすࠊ༡໭  ᡂศ࠾ࡼࡧ✵᣺ࢹ࣮ࢱ  ᡂศࡢィ FKࢆゎീᗘ ELWࠊ+] ࢧࣥࣉࣜࣥࢢ࡛グ㘓ࡍࡿࠋࢹ࣮ࢱࡣෆⶶࡍࡿ *% ࡢ PLFUR6'+& ࡜እ㒊ࡢ 66'࣓ࢹ࢕࢔࡟ಖᏑࡉࢀࡿࠋグ㘓ࣇ࢛࣮࣐ࢵࢺࡣᆅ㟈ほ ࡛ᶆ‽ⓗ࡟⏝࠸ࡽࢀ࡚࠸ࡿ :,1 ࣇ࢛࣮࣐ࢵࢺ࡛࠶ࡿࠋ ᪥ᙜࡓࡾࡢࢹ࣮ࢱ㔞ࡣᅽ⦰≧ែ࡛࠾ࡼࡑ 0% ⛬ᗘ࡟࡞ࡿࠋ௬࡟඲ࢹ࣮ࢱࢆ⾨ᫍ㏻ಙ࡛㏦
ࡿ࡜  ᪥ᙜࡓࡾࡢ㏻ಙᩱ㔠ࡣ⣙  ୓෇ࠊ ࠿᭶ศ࡛ࡣ  ୓෇௨ୖ࡟࡞ࡿࠋࡲࡓࠊ⾨ᫍᅇ⥺ࡣᖏᇦࡀ⊃ࡃ㏻ಙ㏿ᗘࡣ㐜࠸ࠋすஅᓥ࡛ࡢᐇ⦼࡛ࡣ N%V ⛬ᗘ࡜࢝ࢱࣟࢢ್ࡼࡾࡶ㐜࠸ࠋࡇࡢ㏿ᗘ࡛඲ࢹ࣮ࢱࢆ㏦ಙࡍࡿࡓࡵ࡟ࡣ 㹼 ᫬㛫⛬ᗘ᥋⥆ࡍࡿࡇ࡜ࡀᚲせ࡟࡞ࡿࡀࠊ㏻ಙ➃ᮎࡢᾘ㈝㟁ຊࡀ : ࡜኱ࡁ࠸ࡇ࡜࠿ࡽ : ࡢኴ㝧㟁ụ  ᯛ࡛ࡣᏳᐃࡋ࡚㟁ຊࢆ౪⤥࡛ࡁ࡞࠸ࠋࡇࢀࡽࡢ⌮⏤࠿ࡽ඲ࢹ࣮ࢱ
ࢆ㏦ಙࡍࡿࡇ࡜ࡣ᩿ᛕࡏࡊࡿࢆᚓ࡞࠸ࠋ ඲ࢹ࣮ࢱࢆ㏦ࡿ௦ࢃࡾ࡟  ᪥ศࡢࢹ࣮ࢱࡢ࠺ࡕᆅ㟈ィୖୗື  ᡂศ࡟ࡘ࠸࡚ࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝࢆసᡂࡋࠊࡑࢀࢆᅽ⦰ࡋࡓࣇ࢓࢖ࣝࡢࡳࢆẖ᪥㏦ಙࡍࡿࡇ࡜࡜ࡋࡓࠋࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝࡢసᡂ࡟
࠾࠸࡚ࡣ +] ࡢࣁ࢖ࣃࢫࣇ࢕ࣝࢱ࣮ࢆ᥃ࡅࡓ㧗࿘Ἴഃ࡜ +] ࡢ࣮ࣟࣃࢫࣇ࢕ࣝࢱࢆ᥃ࡅ࡚ᚓࡽࢀࡿప࿘Ἴഃ࡟ศࡅࡿࡇ࡜࡛ᗈ࠸࿘Ἴᩘᖏᇦࢆぢࡸࡍࡃ⾲♧ࡍࡿࡇ࡜ࡀ࡛ࡁࡿࠋ⾲♧ࡢ㝿ࠊ๓⪅ࡢ࿘Ἴᩘ㍈ࡣࣜࢽ࢔ࢫࢣ࣮࡛ࣝ࠶ࡾࠊᚋ⪅ࡢ࿘Ἴᩘ㍈ࡣᑐᩘࢫࢣ࣮ࣝ࡜࡞ࡿࠋἼᙧࢹ࣮ࢱࢆ㏦ಙࡍࡿ௦ࢃࡾ࡟
ࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝࡢࢹ࣮ࢱࣇ࢓࢖ࣝࡢࡳࢆ㏦ಙࡍࡿࠋ㏦ಙࣇ࢓࢖ࣝࡢࢧ࢖ࢬࡣ㧗࿘Ἴഃ࡜ప࿘Ἴ
ഃࡑࢀࡒࢀ N%㹼N% ⛬ᗘ࡛࠶ࡾ㏻ಙ㔞ࡣ᭶㛫  ୓෇௨ෆ࡛῭ࡴࠋ࡞࠾ࠊ⌧ᆅ࡟⾜ࡃࡇ࡜ࡀ࡛ࡁ
ࢀࡤእ㒊 66' ࡢ஺᥮࡟ࡼࡾ඲ࢹ࣮ࢱࡢᅇ཰ࡣᐜ࡛᫆࠶ࡿࠋ ࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝసᡂฎ⌮୰࡜ࢹ࣮ࢱ㏦ಙ᫬࡟ࡣࢹ࣮ࢱ࣮ࣟ࢞ࡢᾘ㈝㟁ຊࡀ኱ᖜ࡟ቑ࠼ࡿࠋฎ⌮୰࡟㟁ຊ୙㊊ࡀⓎ⏕ࡍࡿ࡜グ㘓࣓ࢹ࢕࢔ࢆ◚ᦆࡍࡿᜍࢀࡀ࠶ࡿࡓࡵࠊࢹ࣮ࢱฎ⌮࠾ࡼࡧ㏻ಙࡣ᪥↷− 55 −ࡀ࠶ࡾ㟁ຊ࡟వ⿱ࡀ࠶ࡿṇ༗௜㏆࡟⾜࠺ࡼ࠺タᐃࡋࡓࠋࡇࡢタᐃ࡟ࡼࡾ๓᪥ࡲ࡛ࡢ 24 ᫬㛫ศࡢࢹ࣮ࢱࡀ⩣᪥᫨㡭࡟ฎ⌮ࡉࢀ㏦ࡽࢀ࡚ࡃࡿࠋ ࢹ࣮ࢱ࣮ࣟ࢞࡟࠾ࡅࡿ⮬ືฎ⌮ࡢὶࢀࡣ௨ୗࡢᵝ࡟࡞ࡿࠋ࣮ࣟ࢞ࡣ㐃⥆ⓗ࡟ᆅ㟈࣭✵᣺ࢹ࣮ࢱࢆෆⶶ࣓ࢹ࢕࢔࡟グ㘓ࡍࡿ୍᪉ࠊẖᮅ๓᪥ศࡢࢹ࣮ࢱࢆฎ⌮ࡋࠊࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝࡢᅽ⦰ࣇ࢓࢖ࣝࢆ
సᡂࡍࡿࠋࣇ࢓࢖ࣝసᡂࡀ⤊ࢃࡿ࡜ࠊᣦᐃࡉࢀࡓ᫬㛫ᖏ࡟ᆅ㟈◊✲ᡤࡢࢧ࣮ࣂ࣮࡬ࡢ㏻ಙࢆヨࡳࡿࠋ㏻ಙࡀ☜❧࡛ࡁࡓࡽࠊືస≧ែࢆ♧ࡍࣟࢢࣇ࢓࢖ࣝ࡜ࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝࡢᅽ⦰ࣇ࢓࢖ࣝࢆ㏦ಙࡍ
ࡿࠋࡲࡓࠊࢧ࣮ࣂ࣮ഃ࡟ࢲ࣮࢘ࣥࣟࢻࡋࡓ࠸ࣇ࢓࢖ࣝࡢࣜࢫࢺࡀ⏝ពࡉࢀ࡚࠸ࡓሙྜࡣࠊࡑࡢࣜࢫࢺ
࡟ᛂࡌ࡚ࣇ࢓࢖ࣝࢆ㏦ಙࡍࡿࠋᮾி࡬ࡢ㏻ಙࡣࡸࡸ୙Ᏻᐃ࡛ࠊ9 ᭶ࡢタ⨨௨㝆ࡢᐇ⦼࡛ࡣ㏻ಙࡢᡂຌ
⋡ࡣ 6 ๭⛬ᗘ࡛࠶ࡿࠋࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝࢆぢࡿࡇ࡜࡟ࡼࡾᆅ㟈Ⓨ⏕ࡢ᭷↓ࢆ☜ㄆࡍࡿࡇ࡜ࡀ࡛ࡁ
ࡿࠋἼᙧࢹ࣮ࢱࢆᅇ཰ࡋࡓ࠸ሙྜࡣࠊᅇ཰ࡋࡓ࠸ࣇ࢓࢖ࣝࡢࣜࢫࢺࢆࢧ࣮ࣂ࣮ୖ࡟⏝ពࡋ࡚࠾ࡅࡤࠊ
ࢹ࣮ࢱ࣮ࣟ࢞࡜ࢧ࣮ࣂ࣮㛫ࡢ㏻ಙࡀ☜❧࡛ࡁࡓ࡜ࡁ࡟⮬ືⓗ࡟ࣇ࢓࢖ࣝࡀ㏦ಙࡉࢀࡿࠋ௨ୖࡢࢹ࣮ࢱ
ฎ⌮ࡢὶࢀࢆᅗ 4 ࡟♧ࡍࠋ㸰㸫㸲㸬ほ ⿦⨨ࡢタ⨨ タ⨨సᴗࡣ 2019 ᖺ 9 ᭶ 3 ᪥࡜ 4 ᪥ࡢ 2 ᪥㛫࡛⾜ࡗࡓࠋ1 ᪥┠ࡣタ⨨ሙᡤࡢ㑅ᐃࠊᆅ㟈ィᇙタࠊྛᶵჾࡢ௬タ⨨ࠊ᥋⥆ࠊືస☜ㄆࡲ࡛ࢆ⾜࠸ࠊ⩣ᮅࡲ࡛࡟ࢹ࣮ࢱࡀṇᖖ࡟㏦ࡽࢀ࡚࠸ࡿࡇ࡜ࢆ☜ㄆࡋࡓࠋ2 ᪥┠ࡣᶵჾࡢ᭱⤊ⓗ࡞ᅛᐃ࣭㣴⏕ࢆ⾜ࡗࡓࠋ⡆᫆ GPS ࡟ࡼࡿタ⨨఩⨨ࡢᗙᶆࡣ N27°14'45.55", E140r
52'23.85"࡛࠶ࡿࠋ ᆅ㟈ィࡣࠊ㏿஝ࢭ࣓ࣥࢺ࡛ᅛᐃࡋࡓୗᩜࡁࡢୖ࡟Ỉᖹ࡟⨨ࡁࠊᕢ✰ࢆ᥀ࡿ㫽㢮ࡢᙳ㡪ࢆ㑊ࡅࡿࡓࡵ࡟෇⟄࡛ᅖࡗࡓࠋᇙタ῝ᗘࡣ 45 ੉࡛࠶ࡿࠋᅗ 5 ࡟ᆅ㟈ィタ⨨సᴗࡢᵝᏊࢆ♧ࡍࠋ✵᣺ィࡣ⁐ᒾࡢ㝽㛫࡟タ⨨ࡋᒾ࡛࿘ᅖࢆᅖࡗࡓࠋ࣮ࣟ࢞ࡢධࡗࡓ㜵Ỉࢣ࣮ࢫࡣࠊ᫬้ᰯṇ⏝ࡢ GPS ࢔ࣥࢸࢼࡢࡳࢆᆅ⾲࡟ฟࡋࠊ ᗘኚ໬ࡢᙳ㡪ࢆ㑊ࡅࡿࡓࡵࢣ࣮ࢫ඲యࢆᇙタࡋࡓࠋ㏻ಙ➃ᮎࡣ࢔ࣥࢸࢼ㒊ࢆ㏻ಙ⾨ᫍࡢ᪉ྥ࡟ྥࡅࡓ࠺࠼࡛ࠊ࢔ࣥࢸࢼ㒊௨እࢆ▼࡛ᅖࡗࡓ㸦ᅗ 6㸧ࠋ࣮ࣟ࢞࡜㏻ಙ➃ᮎ⏝ࡢ㜵Ỉࢣ࣮ࢫࡣ᪥ᑕᑐ⟇ࡢࡓࡵࠊ࢔࣑ࣝ⵨╔ࢩ࣮ࢺ࡛そࡗ࡚࠶ࡿࠋᅗ 7 ࡟タ⨨ᶵჾࡢ඲ᬒࢆ♧ࡍࠋ㸱㸬ほ ࢹ࣮ࢱࡢ౛ ᮏሗ࿌᭩ᇳ➹᫬Ⅼ㸦2020 ᖺ 1 ᭶ᮎ㸧࡛ほ ࢹ࣮ࢱࡣタᐃࢫࢣࢪ࣮ࣗࣝ㏻ࡾ࡟ᅇ཰ࡉࢀ࡚࠾ࡾࠊ᪥↷୙㊊࡟ࡼࡿḞ ࡀ᫬ᢡⓎ⏕ࡋ࡚࠸ࡿⅬࢆ㝖ࡅࡤタ⨨ᶵჾࡣࡍ࡭࡚㡰ㄪ࡟✌ാ୰࡛࠶ࡿࠋࡇࡇ࡛ࡣࠊ1㸧タ⨨┤ᚋࡢほ Ἴᙧ࡜ࡑࡢ୰࡟ぢࡽࢀࡓ≉␗࡞༟㉺࿘Ἴᩘࢆᣢࡘಙྕࠊ2㸧ᾏὒ₻ộ࡟ᑐᛂࡋ࡚᣺ᖜࡀኚ໬ࡍࡿᵝᏊࠊ3㸧2019 ᖺ 12 ᭶ᄇⅆ࡟క࠺ᆅ㟈࣭✵᣺Ἴᙧࢆ⤂௓ࡍࡿࠋ
㸱㸫㸯㸬ほ 㛤ጞ᫬࡟ぢࡽࢀࡓ≉␗࡞༟㉺࿘ἼᩘࢆᣢࡘἼᙧ ࿘Ἴᩘᖏᇦタ⨨┤ᚋࡢ 9 ᭶ 3 ᪥࠿ࡽ 9 ᭶ 8 ᪥ࡲ࡛ࡢప࿘Ἴഃࡢࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝࢆᅗ 8 ࡟♧ࡍࠋᵝࠎ࡞ࢩࢢࢼࣝࡀᤊ࠼ࡽࢀ࡚࠸ࡿࠋ౛࠼ࡤࠊ0.3㸫0.5Hz ࡢ࿘Ἴᩘᖏᇦ࡛ࡣྎ㢼᥋㏆࡟ࡼࡿἼᾉ࡟
⏤᮶ࡍࡿࣀ࢖ࢬࡀ 9 ᭶ 6 ᪥࠿ࡽᚎࠎ࡟㧗ࡲࡾࠊ9 ᭶ 7 ᪥࡟ࣆ࣮ࢡࢆ㏄࠼ࡿᵝᏊࡀぢ࠼ࡿࠋ0.5㸫2Hz ௜㏆࡟ࡶྎ㢼᥋㏆࡟క࠺ࣀ࢖ࢬࡀぢ࠼ࡿࠋ9 ᭶ 5 ᪥ 1㸸03 㡭࠾ࡼࡧ 7 ᫬ྎ࡜ 10 ᫬ྎ࡟ࠊᓥእ࡛Ⓨ⏕ࡋࡓ࡜᥎ᐃࡉࢀࡿᆅ㟈ࡀᤊ࠼ࡽࢀ࡚࠸ࡿࠋ

− 56 − ⅆᒣάື࡜ࡣ␗࡞ࡿ࡜⪃࠼ࡿ⯆࿡῝࠸ಙྕࡶᤊ࠼ࡽࢀ࡚࠸ࡿࠋᅗ 9 ࡢୖᅗ࡟ 9 ᭶ 3 ᪥ࡢ㧗࿘Ἴഃ㸦0㸫30Hz㸧ࡢࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝࢆ♧ࡍࠋ᫬㛫࡟ࡼࡗ࡚ࢫ࣌ࢡࢺࣝࡢᵓ㐀ࡀኚ໬ࡍࡿࡇ࡜࠿ࡽ
A,B,C,D,E,F ࡢ 6 ࡘࡢ᫬㛫ᖏ࡟ศࡅࠊྛ᫬㛫ᖏࡢᖹᆒࢫ࣌ࢡࢺࣝࢆୗᅗ࡟♧ࡋࡓࠋA ࡣ཰㘓ࢆ㛤ጞࡋࡓ14㸸35 ࠿ࡽ 16㸸00 㡭ࡢᪧᓥୖ࡛ᵝࠎ࡞ㄪᰝࡀ⾜ࢃࢀ࡚࠸ࡿ᫬㛫ᖏ࡛࠶ࡿࠋ20Hz ௜㏆࠿ࡽ᣺ᖜࡀቑຍ
ࡋ 27Hz ௜㏆࡟ࣆ࣮ࢡࡀ࠶ࡿࠋB ࡣ 16㸸00 ࠿ࡽ 18㸸30 ࡢ᪥ἐ๓ࡢ᫬㛫ᖏ࡛ࠊ6 ࡘࡢ᫬㛫ᖏࡢ୰࡛ࡶࡗ
࡜ࡶ㟼࠿࡞᫬㛫ᖏ࡛࠶ࡿࠋC ࡜ F ࡣಙྕࣞ࣋ࣝࡀ㧗ࡃࡸࡸ㈰ࡸ࠿࡞᫬㛫ᖏ࡛࠶ࡿࡀ┠❧ࡗࡓࣆ࣮ࢡࡣ࡞࠸ࠋD ࡣ㈰ࡸ࠿࡞᫬㛫ᖏ࡛࠶ࡾᙉ࠸ಙྕࡀぢ࠼ࡿࠋᅗ࡟♧ࡉࢀ࡚࠸࡞࠸ 30Hz ࡼࡾ㧗࠸࿘Ἴഃ࡟ࣆ
࣮ࢡࡀ࠶ࡿ࡜᥎ᐃࡉࢀࡿࠋE ࡶᙉ࠸ಙྕࡀぢ࠼ࡿ᫬㛫ᖏ࡛࠶ࡾ 15㸫20Hz ௜㏆࡟ࣆ࣮ࢡࡀ࠶ࡿࠋF ࡣኪ᫂ࡅࡲ࡛ࡢࡸࡸ㈰ࡸ࠿࡞᫬㛫ᖏ࡛࠶ࡿࠋ᪥ἐ࠿ࡽᮍ᫂ࡲ࡛ࡢࡸࡸ㈰ࡸ࠿࡞᫬㛫ᖏࡣᪧᓥ࡟ᩘከࡃ⏕ᜥࡍࡿ㫽㢮ࡢάືࢆ཯ᫎࡋ࡚࠸ࡿྍ⬟ᛶࡀ࠶ࡿࡀࠊᆅ㟈グ㘓ࡢࡳ࠿ࡽಙྕ※ࢆ≉ᐃࡍࡿࡇ࡜ࡣ㞴ࡋ࠸ࠋᙉ࠸ಙྕࡢぢ࠼ࡿ D ࡜ E ࡢ᫬㛫ᖏࡣಙྕ※ࡀάⓎ࡞άືࢆ⾜ࡗ࡚࠸ࡿࡇ࡜ࢆ♧၀ࡍࡿࠋ2 ࡘࡢ࿘Ἴᩘᖏᇦ࡟ࣆ࣮ࢡࡀ࠶ࡾࠊࡑࡢ᫬㛫ᖏࡀ␗࡞ࡿࡇ࡜࠿ࡽࠊಙྕ※ࡀ᫬㛫ᖏ࡟ࡼࡗ࡚␗࡞ࡿάືࢆ⾜ࡗ࡚࠸ࡿྍ⬟ᛶࢆ♧၀ࡍࡿࠋྠᵝࡢ≉ᚩࡣ⩣ 9 ᭶ 4 ᪥࡟ࡶぢࡽࢀࡿࠋᅗ 10 ࡣ 9 ᭶ 4 ᪥ࡢࣛࣥࢽࣥࢢࢫ࣌ࢡࢺ
ࣝࢆ 6 ࡘࡢ᫬㛫ᖏ࡟ศࡅࠊྛ᫬㛫ᖏࡢᖹᆒⓗࢫ࣌ࢡࢺࣝࢆ୍⥴࡟♧ࡋࡓࡶࡢ࡛࠶ࡿࠋ9 ᭶ 3 ᪥࡜ྠᵝ࡟᪥୰ࡢ᫬㛫ᖏ A ࡜ C ࡀࡶࡗ࡜ࡶ㟼࠿࡛࠶ࡿࠋࡓࡔࡋㄪᰝ᫬㛫ᖏ࡛࠶ࡿ B ࡣே㛫ࡢάື࡟⏤᮶ࡍࡿಙྕࡀ┠❧ࡘࠋ๓᪥ࡢ 16:00 ࡲ࡛ࡢ᫬㛫ᖏ࡜ྠᵝ࡟ࠊ20Hz ௜㏆࠿ࡽ᣺ᖜࡀቑຍࡋ 27Hz ௜㏆࡟ࣆ࣮ࢡࡀぢࡽࢀࡿࠋ᪥ἐ࠿ࡽᮍ᫂ࡢ D,F ࡢ᫬㛫ᖏࡣࡸࡸ㈰ࡸ࠿࡛࠶ࡾࠊ1㸸30 ࠿ࡽ 3㸸00 ࡲ࡛ࡢ᫬㛫ᖏ࡛࠶ࡿ E ࡛ࡣᙉ࠸ಙྕࡀぢࡽࢀࡿࠋ9 ᭶ 3 ᪥ࡢ DࠊE ࡢ᫬㛫ᖏ࡜ྠᵝ࡟ 15㸫20Hz ࡜ 30Hz ௨ୖࡢ 2 ࠿ᡤ࡟ࣆ࣮ࢡࡀ࠶ࡿࠋ
 9 ᭶ 3ࠊ4 ᪥ࡢ 2 ᪥㛫ࡢグ㘓࠿ࡽᓥෆࡢᆅືࡢ≉ᚩࡣ௨ୗࡢࡼ࠺࡟ࡲ࡜ࡵࡿࡇ࡜ࡀ࡛ࡁࡿࠋ ࣭᪥ࡢฟ࠿ࡽ᪥ἐࡲ࡛ࡀ 1 ᪥ࡢ࠺ࡕ࡛ࡶࡗ࡜ࡶ㟼࠿࡛࠶ࡿࠋ ࣭᪥ἐᚋ࠿ࡽࠊ⩣᪥ࡢฟࡲ࡛ࡸࡸ㈰ࡸ࠿࡞≧ែࡀ⥆ࡃࠋ ࣭῝ኪ࡟ࠊ15㸫20Hz ࡜ 30Hz ௨ୖ࡟ᙉᗘࡢࣆ࣮ࢡࢆᣢࡘ 2 ✀㢮ࡢಙྕ※ࡢάືࡀ࠶ࡿࠋ ࣭ே㛫ࡢάື࡟⏤᮶ࡍࡿಙྕࡣ 20Hz ௜㏆࠿ࡽᙉᗘࢆቑࡋࠊ27Hz ௜㏆࡟ࣆ࣮ࢡࢆᣢࡘࠋ
ኪ㛫࡟ぢࡽࢀࡿ≉ᚩⓗ࡞᣺ືࡣ㫽㢮ࡢάື࡟⏤᮶ࡍࡿྍ⬟ᛶࡀ⪃࠼ࡽࢀࡿࡀࠊᆅ㟈グ㘓ࡢࡳ࠿ࡽಙྕࡢࢯ࣮ࢫࢆ≉ᐃࡍࡿࡇ࡜ࡣ㞴ࡋ࠸ࠋ㫽㢮ࡢ㬆ࡁኌࢆグ㘓ࡍࡿ㡢ኌ࣮ࣟ࢞ࡢグ㘓ࡸᐃⅬ࣓࢝ࣛ⏬ീ࡞࡝ࠊᆅ㟈グ㘓࠿ࡽ⊂❧ࡋࡓࢹ࣮ࢱ࡜ࡢẚ㍑ࡀᚲせ࡛࠶ࢁ࠺ࠋ㸱㸫㸰㸬ᆅື᣺ᖜࡢኚ໬࡜ᾏὒ₻ộ࡜ࡢᑐᛂ 㛗ᮇ㛫ࡢグ㘓࡟ࡣᆅື᣺ᖜࡢ࿘ᮇⓗኚ໬ࡀ᫂░࡟⌧ࢀࡿࠋࡇࢀࡣ₻ộ࡟ࡼࡿᾏỈ㠃ࡢ㧗ࡉࡢኚ໬࡟ᑐᛂࡍࡿ࡜⪃࠼ࡽࢀࡿࠋᅗ 11 ࡣ 9 ᭶ 26 ᪥࠿ࡽ 9 ᭶ 30 ᪥ࡲ࡛ࡢ 5 ᪥㛫࡜ࠊ11 ᭶ 11 ᪥࠿ࡽ 11 ᭶ 15 ᪥ࡲ࡛ࡢ 5 ᪥㛫࡟ࡘ࠸࡚ࠊᆅືࡢࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝ࡜∗ᓥ஧ぢ ࡢ₻ộࢆ୪࡭ࡓࡶࡢ࡛࠶ࡿࠋ₻ộࡣࣇ࣮ࣜࢯࣇࢺࡢ TIDEforWIN㸦http://fmie.cside7.com/㸧ࢆ⏝࠸࡚ィ⟬ࡋࡓࠋすஅᓥ࿘㎶ࡢ₻ộ࡜∗ᓥࡢ₻ộ࡟኱ࡁ࡞᫬㛫ࡎࢀࡣ↓࠸࡜⪃࠼ࡽࢀࡿࡢ࡛ࡇࡢᅗ࡛♧ࡍ⛬ᗘࡢ᫬㛫ゎീᗘ࡟࠾࠸࡚ࡣࠊ஧ぢࡢ₻ộኚ໬ࡣすஅᓥ࿘㎶ࡢ₻ộࢆⰋࡃ㏆ఝࡋ࡚࠸ࡿ࡜⪃࠼ࡽࢀࡿࠋࡇࡢᅗ࠿ࡽࠊᆅືࡢ᣺ᖜኚ໬࡜₻ộኚ໬ࡣ㠀ᖖ࡟ࡼࡃᑐᛂࡋ࡚࠸ࡿࡇ࡜ࡀࢃ࠿ࡿࠋᆅື᣺ᖜ࡜₻ộࡀྠᮇࡍࡿࡇ࡜ࡢཎᅉ࡜ࡋ࡚ࡣࠊᾏỈ㠃ࡀୖ᪼ࡍࡿ࡜Ἴᾉࡀࡼࡾᪧᓥ࡟㏆࠸఩⨨ࡲ࡛㐳ୖࡋࠊἼࡀᡴࡕ௜ࡅࡿࡇ࡜࡛ᆅືࢆບ㉳ࡍࡿ఩⨨− 57 −ࡀᪧᓥ࡟ࡼࡾ㏆࡙ࡃຠᯝ࡞࡝ࡀ⪃࠼ࡽࢀࡿࠋᓥෆ࡛ほ ࡉࢀࡿᆅືࡢኚ໬ࢆゎ㔘ࡍࡿ㝿࡟ࡣࠊ₻ộ࡟ࡼࡿຠᯝࡶ⪃៖ࡋ࡞ࡅࢀࡤ࡞ࡽ࡞࠸ࡇ࡜ࡀࢃ࠿ࡿࠋ㸱㸫㸱㸬 ᖺ  ᭶ᄇⅆ࡟క࠺ᆅ㟈࣭✵᣺Ἴᙧ 2019 ᖺ 12 ᭶ 4 ᪥࡟すஅᓥࡢⅆᒣάືࡀ෌㛤ࡋࡓࠋᅗ 12 ࡣ 12 ᭶ 4 ᪥࠿ࡽ 6 ᪥࡟࠿ࡅ࡚ࡢᆅືࠊᆅ
ືࡢࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝࠊ✵᣺ࢆ୪࡭ࡓࡶࡢ࡛࠶ࡿࠋ12 ᭶ 4 ᪥᫨㡭࠿ࡽᆅື᣺ᖜࡢቑຍࡀጞࡲࡾࠊ
12 ᭶ 5 ᪥ᮍ᫂࡟ࡣᄇⅆ࡟ᑐᛂࡍࡿ✵᣺άືࡀጞࡲࡗࡓࠋ12 ᭶ 5 ᪥᫨㐣ࡂ࡟ࡣᆅ㟈ࠊ✵᣺ࡢ୧⪅࡟኱᣺ᖜࡢಙྕࡀ⌧ࢀࠊ16 ᫬㐣ࡂ࡟≉࡟኱ࡁ࡞ಙྕࡀᤊ࠼ࡽࢀ࡚࠸ࡿࠋࡑࢀ௨㝆ࡣ኱ࡁ࡞᣺ᖜࡢᆅືࠊ✵᣺ࡀ࡯ࡰ㐃⥆ⓗ࡟⥆࠸࡚࠸ࡿࠋேᕤ⾨ᫍ࡟ࡼࡿ㉥እ⏬ീ࡟ࡼࡿ࡜ࠊ12 ᭶ 4 ᪥ࡢ 20 ᫬㡭࡟๓㥑ⓗ࡞⇕␗ᖖࡀึࡵ࡚ほ ࡉࢀࠊ12 ᭶ 5 ᪥ 15 ᫬௨㝆ࡣ⁐ᒾὶฟࢆ♧၀ࡍࡿᙉ࠸⇕␗ᖖࡀほ ࡉࢀ࡚࠸ࡿ㸦㔠Ꮚࠊ⚾ಙ㸧ࠋ2017 ᖺ 4 ᭶ࡢᄇⅆ࡛ࡣᆅ㟈グ㘓࡟࠸ࡕ᪩ࡃ␗ᖖࡀ⌧ࢀࡓࡀࠊ௒ᅇࡶᆅ㟈グ㘓࡟᭱ึ࡟ኚ໬ࡀ
⌧ࢀࡓࠋࡇࡢࡇ࡜ࡣࠊᆅ㟈ࡢࣔࢽࢱࣜࣥࢢ࡟ࡼࡾ᪩࠸ẁ㝵࡛ⅆᒣάືࡢ㛤ጞࢆᤊ࠼ࡽࢀࡿࡇ࡜ࢆ♧ࡋ࡚࠸ࡿࠋ㸲㸬ࡲ࡜ࡵ すஅᓥࡢᪧᓥ㒊࡟ᆅ㟈ィ࡜✵᣺ィࢆ෌タ⨨ࡋ⾨ᫍ㏻ಙࢆ㏻ࡌ࡚ⅆᒣάືࢆࣔࢽࢱࣜࣥࢢࡍࡿࡇ࡜ࡀྍ⬟࡟࡞ࡗࡓࠋᆅ㟈グ㘓࡟ࡣᵝࠎ࡞ᆅືࡀ᫂░࡟ᤊ࠼ࡽࢀ࡚࠾ࡾࠊࡑࡢ୰࡟ࡣᓥෆእࡢᆅ㟈ࠊᆅ㟈࣭ⅆᒣάື௨እ࡟㉳ᅉࡍࡿ࡜ᛮࢃࢀࡿᆅືࡀྵࡲࢀ࡚࠸ࡿࠋᓥෆࡢᆅ㟈ࢹ࣮ࢱࡣⅆᒣάືࡢࣔࢽࢱࣜࣥࢢ࡟࡜ࡗ࡚᭷⏝࡛࠶ࡿࡀࠊⅆᒣάື࡜ࡣ␗࡞ࡿཎᅉ࡛Ⓨ⏕ࡋ࡚࠸ࡿ࡜⪃࠼ࡽࢀࡿ≉ᚩⓗ࡞ᆅື࡟ࡘ࠸࡚ࡶࠊすஅᓥࡢᵝࠎ࡞άືࢆホ౯ࡍࡿୖ࡛ࡢᇶ♏ࢹ࣮ࢱ࡜࡞ࡾᚓࡿࠋ௒ᚋ᭦࡞ࡿࢹ࣮ࢱࡢ⵳✚࡜ヲ⣽࡞ゎᯒࡀᚲせ࡛࠶ࡿࠋ すஅᓥࡣ 2019 ᖺ 12 ᭶ 4 ᪥࡟ᄇⅆάືࢆ෌㛤ࡋࠊᮏሗ࿌᭩ᇳ➹᫬Ⅼ㸦2020 ᖺ 1 ᭶㸧࡟࠾࠸࡚ࡶάືࡀ⥅⥆ࡋ࡚࠸ࡿࠋすஅᓥࡣ௒ᚋࡶᄇⅆάືࡢάⓎ໬࡜೵Ṇࢆ⧞ࡾ㏉ࡋ࡞ࡀࡽᚎࠎ࡟⤊ᜥ࡟ྥ࠿࠺࡜⪃࠼ࡽࢀࡿࠋᮏほ ࡟࠾࠸࡚ࡣᆅ㟈ィ࡜✵᣺ィࢆᪧᓥ㒊ศ࡟タ⨨ࡍࡿࡇ࡜࡟ࡼࡾࠊⅆᒣάືࡢ᥎⛣ࢆ⥅⥆ⓗ࡟ᢕᥱࡍࡿ࡜࠸࠺┠ᶆࢆᐇ⌧࡛ࡁࡓࠋ௒ᚋࠊ⁐ᒾὶ࡟ࡼࡿほ ⿦⨨ࡢᇙἐࡸࠊᄇ▼࡟ࡼࡿኴ㝧㟁ụࡢ◚ᦆ࡞࡝ࡢ༴㝤ࡣṧࡿࡶࡢࡢࠊⅆᒣάືࡀࡇࢀ௨ୖάⓎ໬ࡋ࡞ࡅࢀࡤほ ࢆ⥅⥆࡛ࡁࡿྍ⬟ᛶࡣ༑ศ࡟࠶ࡿࠋほ ࡀ⥅⥆࡛ࡁࢀࡤࠊάືࡀ㟼✜໬ࡋࡓ㝿࡟⾜ࢃࢀࡿ࡛࠶ࢁ࠺ᑗ᮶ࡢྛ✀ㄪᰝᐇ᪋᫬࡟ⅆᒣάືࢆᢕᥱࡍࡿࡇ࡜࡛Ᏻ඲⟶⌮࡟㈨ࡍࡿࡇ࡜ࡀᮇᚅࡉࢀࡿࠋ
㸳㸬ㅰ㎡

ᮏୖ㝣ㄪᰝࡣ⎔ቃ┬ࡢࠕ௧࿴ඖᖺᗘすஅᓥ⥲ྜᏛ⾡஦ᴗࠖ࡟ࡼࡾᐇ᪋ࡋࡓࡶࡢ࡛࠶ࡿࠋᐇ᪋࡟ᙜࡓࡾ㛵ಀྛᶵ㛵࡟ከ኱࡞౽ᐅࢆᅗࡗ࡚࠸ࡓࡔ࠸ࡓࠋࡇࡇ࡟グࡋ࡚ឤㅰࢆ⏦ࡋୖࡆࡓ࠸ࠋ㸴㸬ᘬ⏝ᩥ⊩Ṋᑿ ᐇ࣭኱‖ 㝯㞝࣭๓㔝 ῝࣭⠛ཎ 㞞ᑦ࣭㤿ሙ ⪷⮳࣭Ώ㑓 ⠜ᚿ࣭ᕷཎ ⨾ᜨ࣭す⏣ ✲࣭㔠Ꮚ 㝯அ࣭Ᏻ⏣ ᩔ࣭ᮡᒸ ⿱Ꮚ࣭὾㔝 ὒ୕࣭ከ⏣ カᏊ࣭୰㔝 ಇ࣭ྜྷᮏ ඘ᏹ࣭㧗ᮌ ᮁ඘࣭㛗ᒸ ඃ㸦2018㸧 すஅᓥࡢᆅ⌫≀⌮ほ ࡜ୖ㝣ㄪᰝ. ᾏὒ⌮ᕤᏛ఍ㄅ 24(1): 45㸫56.
๓㔝 ῝࣭Ᏻ⏣ ᩔ࣭୰㔝 ಇ࣭ྜྷᮏ ඘ᏹ࣭኱‖ 㝯㞝࣭Ώ㑓 ⠜ᚿ࣭㔠Ꮚ 㝯அ࣭୰⏣ ⠇ஓ࣭Ṋᑿ ᐇ− 58 −

(2018) ᄇฟ≀࠿ࡽ᥈ࡿすஅᓥࡢ᪂ⅆᒣᓥᙧᡂࣉࣟࢭࢫ. ᾏὒ⌮ᕤᏛ఍ㄅ 24(1): 35-44.
Ώ㑓 ⠜ᚿ࣭኱‖ 㝯㞝࣭Ṋᑿ ᐇ㸦2017㸧 すஅᓥⅆᒣ࡬ࡢほ Ⅼタ⨨. ᮾி኱Ꮫᆅ㟈◊✲ᡤᢏ⾡◊✲ሗ࿌ 23: 1-9.


− 59 −

⾲ 1. ほ ࡟⏝࠸ࡓᶵᮦ୍ぴTable 1. List of the instrumentsᶵᮦᆺᘧ/〇㐀ඖࢧ࢖ࢬࠊእᙧ

ㅖඖ࡞࡝

Instruments

Model/manufacturer

physical size

Specification

ᆅ㟈ィTrillium 120 Compact PH/┤ᚄ 9.7 ੉ࠊ

Seismometer

Nanometrics

㧗ࡉ 16.7 ੉✵᣺ィSI-104/┤ᚄ 3 ੉ࠊ㛗ࡉ 10 ੉

0.1 - 1500Hz

Infrasound sensorⓑᒣᕤᴗࢹ࣮ࢱ࣮ࣟ࢞

SC-ADHIMG2/

17 ੉×15 ੉×8.4 ੉

100Hz, 22bit, AD, 2W,

Data loggerࢩࣔࣞࢵࢡࢫ♫⾨ᫍ㏻ಙ➃ᮎThuraya IP+ /Satellite data modem

Thuraya ♫ኴ㝧㟁ụ

GT20(2 ᯛ)/

Solar panelࢣ࣮࣭࢔࢖࣭࢚ࢫ♫ࣂࢵࢸ࣮ࣜ

G26EP /

BatteryEnerSys ♫120s - 150Hz

32GB
22 ੉×22 ੉

444kbps
14.4W

53.8 ੉×35 ੉

24W (×2)

17.6 ੉×8.4 ੉×13 ੉

12V, 26Ah, 10.8kg

− 60 −

ᅗ 1 2016 ᖺ 10 ᭶࡜ 2019 ᖺ 9 ᭶ࡢᆅ㟈࣭✵᣺ほ ⿦⨨ࡢタ⨨఩⨨⡆᫆ *36 ࡟ࡼࡿ௒ᅇࡢタ⨨఩⨨ࡣ 1r (r 㸬ᅜᅵᆅ⌮㝔  ᖺ  ᭶  ᪥᧜ᙳ⏬ീࢆ౑⏝ࠋ
Figure 1. Locations where seismic and infrasound sensors were installed in October 2016 and in September 2019ᅗ 2 ほ ᶵᮦࡢእほFigure 2. Instruments used for Nishinoshima observation
From top-left to bottom-right, seismometer, infrasound sensor, data-logger, satellite data modem, solar panel, andbattery..

− 61 −



ᅗ 3 㜵Ỉࢣ࣮ࢫ࡟ධࢀࡓ≧ែࡢほ ᶵᮦ
Figure 3. Data logger, battery and satellite data modem in the water-proof pelican case.

ᅗ 4 ࢹ࣮ࢱฎ⌮ࡢὶࢀ⦕ྲྀࡾ▮༳ࡣ⮬ືฎ⌮ࠊሬࡾࡘࡪࡋ▮༳ࡣᡭື࡛⾜࠺᧯సࢆ⾲ࡍ㸬
Figure 4. Flow of data acquisition and processing
Bordered arrows indicate automatic processing, and closed arrows show manual operation.

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ᅗ 5 ᆅ㟈ィࡢタ⨨ࡢᵝᏊFigure 5. How to install the seismometer.

ᅗ 6 ྛᶵჾࡢタ⨨≧ែ㸸ᆅ㟈ィࠊኴ㝧㟁ụࠊ✵᣺ィࠊ࣮ࣟ࢞࡜㏻ಙ➃ᮎFigure 6. Installed observation equipment at Nishinoshima: Seismometer (top-left), solar panels (top-right),
infrasound sensor (bottom-left), data-logger and satellite data modem (bottom-right)− 63 −

ᅗ 7 タ⨨ࡉࢀࡓᶵჾࡢ඲ᬒ
Figure 7. Overview of the installed equipment
ᅗ 8 ప࿘Ἴഃࡢࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝ㸦2019 ᖺ 9 ᭶ 3 ᪥࠿ࡽ 9 ᭶ 8 ᪥ࡲ࡛㸧ྛࣃࢿࣝ࡟࠾࠸࡚ࠊ⦪㍈ࡣᑐᩘ┠┒࡛♧ࡋࡓ࿘Ἴᩘ(0.01-10Hz)ࠊᶓ㍈ࡣ༗๓ 5 ᫬࠿ࡽ⩣᪥༗๓ 5 ᫬ࡲ࡛ࡢ᫬㛫ࠋ0.1Hz ࡼࡾప࠸ᖏᇦ࡟ࡣࢹ࣮ࢱฎ⌮ୖࡢࣀ࢖ࢬࡀ࠶ࡿࡓࡵ࣐ࢫࢡࡉࢀ࡚࠸ࡿࠋ
Figure 8. Running spectrum of seismic signals at lower-frequency band (0.01-10Hz)
From September 3 to September 8, 2019. Vertical axis shows frequency (0.01-10Hz) in logarithmic scale. Horizontal
axis shows time from 5 am on a certain day to 5 am on the next day. Lower than 0.1Hz is masked to avoid noise
originated from data processing.㻌

− 64 −ᅗ 9 ୖᅗ㸸୍᪥ศࡢ㧗࿘Ἴഃࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝ
ᶓ㍈ࡣ 9 ᭶ 3 ᪥ 5㸸00 ࠿ࡽ 4 ᪥ 5㸸00 ࡲ࡛ࡢ᫬㛫ࠊ⦪㍈ࡣ࿘Ἴᩘࠋࢫ࣌ࢡࢺࣝࡢ≉ᚩ࡟ᛂࡌ࡚
A,B,C,D,E,F ࡢ 6 ࡘࡢ᫬㛫ᖏ࡟ศࡅࡽࢀࡿࠋୗᅗ㸸6 ࡘ࡟ศࡅࡓྛ᫬㛫ᖏࡢᖹᆒⓗࢫ࣌ࢡࢺࣝࠋFigure 9. Top: Running spectrum for one day
Horizontal axis is the time from 5 am on September 3 to 5 am on the next day. Vertical axis is the frequency (0-30Hz).
It is divided into six time zones A, B, C, D, E and F according to the characteristics of the spectrum. Bottom: Averagedspectrum in each time zone in the top panel.

− 65 −ᅗ 10 ୖᅗ㸸୍᪥ศࡢ㧗࿘Ἴഃࣛࣥࢽࣥࢢࢫ࣌ࢡࢺࣝ
ᶓ㍈ࡣ 9 ᭶ 4 ᪥ 5㸸00 ࠿ࡽ 5 ᪥ 5㸸00 ࡲ࡛ࡢ᫬㛫ࠊ⦪㍈ࡣ࿘Ἴᩘࠋࢫ࣌ࢡࢺࣝࡢ≉ᚩ࡟ᛂࡌ࡚
A,B,C,D,E,F ࡢ 6 ࡘࡢ᫬㛫ᖏ࡟ศࡅࡽࢀࡿࠋୗᅗ㸸ୖᅗࡢྛ᫬㛫ᖏࡢᖹᆒⓗࢫ࣌ࢡࢺࣝࠋFigure 10. Top: Running spectrum for one day. Horizontal axis is the time from 5 am on September 4 to 5 am on thenext day
Vertical axis is the frequency (0-30Hz). It is divided into six time zones A, B, C, D, E and F according to thecharacteristics of the spectrum. Bottom: Averaged spectrum in each time zone in the top panel.

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ᅗ 11 ࿘Ἴᩘᖏᇦ 0-5Hz ࡢ᣺ᖜኚ໬࡜₻ộኚ໬ࡢᑐᛂ₻ộࡣ∗ᓥ஧ぢ ࡛ࡢ᪥ኚ໬ࠋ
Figure 11. Correlation between the seismic amplitude at 0-5Hz frequency range and the ocean tide
The shown tide is the daily change at Futami port in Chichijima.

ᅗ 12 2019 ᖺ 12 ᭶ 4 ᪥ࡢᆅ㟈ື࡜✵᣺12 ᭶ 4 ᪥᫨㡭࠿ࡽ᣺ᖜࡢቑຍࡀጞࡲࡾࠊ12 ᭶ 5 ᪥ࡢ᪩ᮅ࡟ᄇⅆ㛤ጞࢆ♧ࡍ✵᣺ࡀほ ࡉࢀࡓࠋ12 ᭶5 ᪥ࡢ 16 ᫬㐣ࡂ࡟኱᣺ᖜࡢᆅ㟈࣭✵᣺ࡀほ ࡉࢀࡓࠋFigure 12. Seismic and infrasound signal on December 4, 2019
Seismic amplitude began to increase around noon, December 4. Infrasound signal corresponding to volcanic
eruptions started early in the morning on December 5. At 16:13, December 5, large amplitude seismic and infrasoundsignals were observed.

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OGASAWARA RESEARCHSUMMARY

Seismic and Infrasound observation at Nishinoshima Island in 2019
Takao OHMINATO1* & Atsushi WATANABE1
Earthquake Research Institute, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-0032, Japan.
* takao@eri.u-tokyo.ac.jp (author for correspondence)
For the purpose of monitoring the volcanic activity at Nishinoshima volcanic island, we installed an observation
station composed of a seismometer and an infrasound sensor on the old part of Nishinoshima on September 3-4,
2019. The observation station consists of a broadband-seismometer, an infrasound microphone, a data logger, asatellite communication modem, solar panels, and a battery. The seismic and infrasound data are digitized by the datalogger and are recorded on the built-in media. The logger calculates the running spectrum of the ground motion data,compresses it, and sends it to a data server in Earthquake Research Institute via a satellite link. With this dataprocessing and data-transmission mechanism, it is possible to obtain continuous information of the ground motion
necessary for evaluating seismic activity while using a narrow satellite line. It is possible to monitor the volcanic
activity using the continuous running spectrum, and if necessary, it is also possible to transmit the original
uncompressed seismic / infrasound waveform data from the logger.
The observation station installed on the old part of Nishinoshima has detected not only ground motion caused byvolcanic activity, but also ground motion from a variety of sources, and the basic data that is important forunderstanding various activities on the island has been accumulated. The volcanic activity of Nishinoshima resumed
in December 2019. Since the observation station was able to detect earthquakes and infrasound signals associatedwith the volcanic activity earlier than any other volcano monitoring methods, it has been shown that this station would
contribute to the future safety management of research activities in and around Nishinoshima.

Key words
Satellite data transmission, Volcanic earthquakes, Volcano monitoring− 68 −