Report on DELP 1986 Cruises in the Northwestern Pacific : Part II: Oceanic Crust of the Basin

Abstract

A large scale seismic experiment was carried out in the northwestern Pacific Basin in 1986. Two long range profiles were shot using OBS's and explosives to investigate the nature of the lateral heterogeneity and anisotropy of an old oceanic lithosphere. An airgun array was also used as a controlled seismic source. Three airgun profiles were shot in order to obtain a detailed crustal structure of normal ocean type and to constrain the deeper structure obtained from the long range profiles. A seismic wavespeed model for both P and S waves is presented. The model seems adequate to represent the crust sampled over 700km distance. The model is in good areement with the model previously obtained near DSDP Hole 581C. However, our data do not substantiate the presence of LVZ in the lower crust.1986年北西太平洋海盆において大規模地震探査実験が行なわれた. 2本の長距離測線から,火薬とOBSを用いて古い海洋リソスフィアの水平不均質と異方性を調べるためである.エアガンアレーも制御震源として用いた.標準海洋地殻を詳しく求めるためおよび,大規模構造の深部の解像度をあげるため3本のエアガン測線データも得た