Oldest Array

The first Pacific Array deployment by the Japanese group is just about to be conducted in the oldest part of the Pacific Ocean seafloor as a collaboration with Koreans. We aim to deploy two arrays to investigate the lithosphere-asthenosphere system of the oldest Pacific Plate that should record the birth processes of the Pacific plate 180 million years ago, as well as the history of its evolution.



Fig. 1. Oldest array consists of two arrays, Oldest-1 (open triangles) and Oldest-2 (solid triangles). White circles denote small-span "spiral" arrays. Oldest-1 will be deployed in 2018 (Oct. 30-Nov. 10) as an acollaboration between Japan and Korea. Oldest-2 is proposed to be deployed in 2020-2021.

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Fig. 2 Early history of the Pacific Plate (Seton et al., 2012).



Fig. 3 Oldest: the least understood part of the Pacific mantle? (e.g., Becker et al., 2014, EPSL).




Fig. 4 What to resolve (1): seismic anisotropy. The dynamics of the birth of the Pacific plate should be recorded in the lithosphere as seismic anisotropy. Input anisotropy represented by bars (3% azimuthal anisotropy whose fast directions are perpendicular to the magnetic lineations) can be recovered via seismic tomography utlizing array data (cases without and with Oldest arrays are shown; white regions indicate good illumination).