To clarify the process by which intraplate earthquakes are generated -A dense seismic observation in the northern part of the South Island in New Zealand-

• Project/Area Number: 15H05206
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 海外学術
• Research Field: Solid earth and planetary physics
• Research Institution: Kyoto University
• Principal Investigator: IIO Yoshihisa 京都大学, 防災研究所, 教授 (50159547)
• Co-Investigator(Kenkyū-buntansha): 岡田 知己 東北大学, 理学研究科, 准教授 (30281968) ; 松本 聡 九州大学, 理学研究院, 准教授 (40221593)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Project Status: Completed (Fiscal Year 2017)
• Budget Amount: ¥16,380,000 (Direct Cost: ¥12,600,000、Indirect Cost: ¥3,780,000); Fiscal Year 2017: ¥4,810,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥1,110,000); Fiscal Year 2016: ¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000); Fiscal Year 2015: ¥7,410,000 (Direct Cost: ¥5,700,000、Indirect Cost: ¥1,710,000)
• Keywords: 内陸地震 / 水 / ニュージーランド / 断層 / 観測 / ニュージーランド南島 / 地震観測

Outline of Final Research Achievements

We continued a dense seismic observation in the northern part of the South Island in New Zealand, and installed 3 new stations around the north-western end of the South Island where no seismic stations are operated. By analyzing recorded data, we obtained the results that support the hypothesis that water upwelling from subducting plates reaches to the lower crust and generates intraplate earthquakes. The Kaikoura earthquake Mw(7.8) occurred within our seismic network on December, 14th, 2016. We installed 4 new stations near the hypocenter of the main shock, and succeeded the maintenance of seismic stations to which accesses are difficult owing to road closed, and obtained valuable data. We estimated detailed hypocentral distributions and stress fields before and after the main shock.

Research Products

• [Presentation] Three-dimensional seismic velocity structure beneath the northern South Island, New Zealand from dense seismic observation (2017)
  • Author(s): T. Okada, Y. Iio, S. Matsumoto, S.Bannister, S. Ohmi, S. Horiuchi, T. Sato, T. Miura, J. Pettinga, F. Ghisetti, R. H. Sibson
  • Organizer: IAG-IASPEI 2017
  • Int'l Joint Research
• [Presentation] Regional stress field inferred from focal mechanisms obtained by dense seismic observation in the northern South Island, New Zealand (2017)
  • Author(s): T. Sato, T. Okada, Y. Iio, S. Matsumoto, S. Bannister, J. Ristau, S. Ohmi, T. Miura, J. Pettinga, F. Ghisetti, R. H. Sibson
  • Organizer: IAG-IASPEI 2017
  • Int'l Joint Research
• [Presentation] 稠密地震観測で求めた、東北沖地震後の内陸誘発地震震源域の応力場 (2017)
  • Author(s): 岡田知己・中山貴史・平原聡・堀修一郎・佐藤俊也・松澤暢・吉田圭佑・長谷川昭・2011年東北地方太平洋沖地震合同余震観測グループ
  • Organizer: 日本地震学会2017年度秋季大会
• [Presentation] ニュージーランド南島北部における2016 Mw 7.8 Kaikoura地震前後での広域応力場の推定とその変化 (2017)
  • Author(s): 佐藤将・岡田知己・飯尾能久・大見士朗・三浦勉・ 松本聡・S. Bannister・J. Ristau・J. Pettinga・F. Ghisetti・R. Sibson
  • Organizer: 日本地震学会2017年度秋季大会
• [Presentation] SEISMIC TOMOGRAPHY IN THE NORTHERN SOUTH ISLAND AND THE 2016 KAIKOURA EARTHQUAKE (2017)
  • Author(s): T. Okada, Y. Iio, S. Matsumoto, S.Bannister, S. Ohmi, S. Horiuchi, T. Sato, T. Miura, J. Pettinga, F. Ghisetti, R. H. Sibson
  • Organizer: GEOSCIENCE SOCIETY OF NEW ZEALAND ANNUAL CONFERENCE 2017
  • Int'l Joint Research
• [Presentation] SPATIO-TEMPORAL REGIONAL STRESS FIELD ASSOCIATED WITH THE MW 7.8 KAIKOURA EARTHQUAKE BY STRESS TENSOR INVERSION IN THE NORTHERN SOUTH ISLAND (2017)
  • Author(s): T. Sato, T. Okada, Y. Iio, S. Matsumoto, S. Bannister, J. Ristau, S. Ohmi, T. Miura, J. Pettinga, F. Ghisetti, R. H. Sibson
  • Organizer: GEOSCIENCE SOCIETY OF NEW ZEALAND ANNUAL CONFERENCE 2017
  • Int'l Joint Research
• [Presentation] Three-dimensional crustal seismic velocity structure in the northern part of the South Island, New Zealand (2016)
  • Author(s): Tomomi Okada, Yoshihisa Iio, Satoshi Matsumoto, Richard H. Sibson and members of the Lyell-Murchison Project
  • Organizer: Workshop on the Deep Fault Drilling Project (DFDP) - Alpine Fault
  • Place of Presentation: 高山市
  • Year and Date: 2016-07-18