[S-SS10] Seismic wave propagation: Theory and Application

[SSS10-P04] Array analysis on the temporal change of seismic velocity structure detected with ACROSS signal in Sakurajima volcano, Japan.

*Koshun Yamaoka¹, Kosei Saeki¹, Shuhei Tsuji¹, Eisuke Fujita⁴, Hiroki Miyamachi², Toshiki Watanabe¹, Takahiro Kunitomo¹, Hiroshi Yakiwara², Ryoya Ikuta³, Takeshi Tameguri⁵, Masato Iguchi⁵ (1.Earthquake and Volcano Research Center, Graduate School of Environmental Studies, Nagoya University, 2.Graduate School of Science and Engineering, Kagoshima Univerisyt, 3.Faculty of Science, Shizuoka Univeristy, 4.National Institute for Earth Science and Disaster Resilience, 5.Disaster Prevension Research Institute, Kyoto University)

Keywords:magma intrusive event, seismic velocity variation

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.