Studies on S-wave attenuation structure in Nankai subduction zone for feature extractions of medium properties

2015 Fiscal Year Final Research Report

• Project/Area Number: 25800255
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Solid earth and planetary physics
• Research Institution: Japan Agency for Marine-Earth Science and Technology
• Principal Investigator: Takahashi Tsutomu 国立研究開発法人海洋研究開発機構, 地震津波海域観測研究開発センター, 主任研究員 (90435842)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: 地震波散乱 / 内部減衰 / 南海トラフ / マルコフ連鎖モンテカルロ法

Outline of Final Research Achievements

This study estimated the S-wave attenuation structure in Nankai subduction zone with correction terms for apparent attenuation due to multiple wave scattering. Beppu-Shimabara rift zone shows high attenuation as with other volcanic areas, but this area has a unique vertical variation of random inhomogeneity. This result suggests that temperature beneath this rift zone would be similar with other volcanic areas, but inclusions of magma or volcanic rocks would be poorer than other volcanic areas. Near the top of the subducting Philippine Sea plate, moderately high attenuation zones were imaged over the Nankai subduction zone. Some of them are coincident with non-volcanic tremor zones. We discussed possible relations among random inhomogeneity, attenuation and tremor triggering in terms of fluid oscillation, and pointed out some conditions for dynamic triggering of tremors.

Free Research Field

地震学