Estimation of shear wave velocity structure at shallow ocean bottom, by using synthetic waveforms that rigorously handles the complex structures in the vicinity of seafloor

2016 Fiscal Year Final Research Report

• Project/Area Number: 15H06904
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Single-year Grants
• Research Field: Solid earth and planetary physics
• Research Institution: Japan Agency for Marine-Earth Science and Technology
• Principal Investigator: TOH Akiko 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, 研究員 (70587344)
• Research Collaborator: CAPDEVILLE Yann Universite de Nantes
• Project Period (FY): 2015-08-28 – 2017-03-31
• Keywords: スペクトル要素法 / 広帯域海底地震計 / S波速度構造 / Neighborhood algorithm

Outline of Final Research Achievements

We aim to construct S-wave velocity structural model using records of ocean bottom seismometers for the shallow seduction zone of Nankai trough where mega-thrust earthquake occurs repeatedly. The S waveforms recorded by the ocean bottom seismometers are heavily distorted by propagating through slow layers in the vicinity of ocean bottom. In this study, we first quantitatively evaluated such distortions by constructing synthetic waveforms using spectral element method. Also we conducted feasibility tests of probabilistic full waveform inversion using Neighborhood algorithm.
During the latter half of the project period, we focused on analyses of very low frequency earthquakes that occurred in the target region in October 2015. We revealed their spatial distribution with respect the shallow subduction zone structure.

Free Research Field

地震学