JpGU-AGU Joint Meeting 2017

講演情報

[EE]Eveningポスター発表

セッション記号 S (固体地球科学) » S-SS 地震学

[S-SS04] [EE] Subduction zone dynamics from regular earthquakes through slow earthquakes to creep

2017年5月24日(水) 17:15 〜 18:30 ポスター会場 (国際展示場 7ホール)

[SSS04-P31] Shallow Slow Slip Event Off the Kii Peninsula in April 2016, Japan

*板場 智史1案浦 理2橋本 徹夫2鎌谷 紀子2勝間田 明男3 (1.産業技術総合研究所 活断層・火山研究部門、2.気象庁 地震火山部、3.気象研究所 地震津波研究部)

キーワード:SSE, Slow earthquake, Low frequency earthquake

On 1 April 2016, an earthquake (Mw=5.9, hereafter mainshock, USGS) occurred off the Kii Peninsula, Japan. The mainshock occurred around the expected focal region of the so-called Tonankai earthquake. After the mainshock, strain and pore-pressure changes caused by the slow slip event (SSE) were observed by the three borehole strainmeters of AIST. The source region of this SSE is located on the plate interface at southeast side of the mainshock. An equivalent magnitude of this SSE is Mw 6.0, and duration is about 7 days. From after just a few days from the mainshock, in and around this SSE source region, intensive activity of shallow low frequency tremor has been observed for about two weeks, it is assumed that these shallow tremor events were induced by this SSE.
In off the Kii Peninsula, VLF and Low Frequency Earthquake has been often observed, but SSE had not been observed by geodetic method. The slip deficit rate of this SSE source region is about 3 cm / year (Yokota et al., 2016), and the plate convergence rate is 5.0 to 6.5 cm / year (Heki and Miyazaki, 2001). Therefore, in addition to this case, there is a possibility that SSE frequently occurred in this region.

References
Heki, K. and S. Miyazaki, Plate Convergence and Long-Term Crustal Deformation in Central Japan,. Geophys. Res. Lett., 28, 2313-2316, 2001.
Yokota, Y., T. Ishikawa, S. Watanabe, T. Tashiro, and A. Asada, Seafloor geodetic constraints on interplate coupling of the Nankai Trough megathrust zone, Nature, 534, 374-377, doi:10.1038/nature17632, 2016.