[S-SS10] 地震波伝播：理論と応用

[SSS10-P04] 地震計アレイとアクロスで捉えた2015年桜島マグマ貫入にともなう地震波伝播特性の変化

*山岡 耕春¹、佐伯 晃聖¹、辻 修平¹、藤田 英輔⁴、宮町 宏樹²、渡辺 俊樹¹、國友 孝洋¹、八木原 寛²、生田 領野³、為栗 健⁵、井口 正人⁵ (1.名古屋大学環境学研究科附属地震火山研究センター、2.鹿児島大学大学院理工学研究科、3.静岡大学理学部、4.防災科学技術研究所、5.京都大学防災研究所)

キーワード：マグマ貫入、地震波速度変化

We detected a temporal change in propagation property of seismic wave using seismic array associated with a magma intrusive event on 15 August 2015 of Sakurajima volcano, Japan. We performed an array signal processing for the signal of an accurately controlled seismic source (ACROSS), that is located to the northwest of the summit, for two seismic arrays deployed by NIED. The two array, SKN and SKE, are located to the northeast and east of the summit, respectively. For the array analysis we used semblance analysis for three periods, 23 July 2015 to 8 August 2015 (Period 1), 9 August 2015 to 7:00 of 15 August 2015 (Period 2) and 9:00 of 15 August 2015 to 19 August 2015 (Period 3). In the array data large difference is observed between Period 2 and 3, although little difference is observed between Period 1 and 2. The large difference is apparently caused by the intrusive event of Sakurajima volcano on 15 August 2015. The change associated with the intrusive event does not appear in the initial arrival at SKN but appears in the later part, indicating change in the subsurface scattering nature. The scattering point can be estimated assuming single scattering using semblance data. On the other hand SKE shows scattered difference between Period 2 and 3 indicating distributing subsurface scattering points.