Active source seismic studies across/along across-arc seamount chains in Izu-Bonin arc –Cruise report of KR0601 and KR0605–

Abstract

In order to investigate formation processes of the across-arc sea mount chains in the Izu-Bonin arc, we have carried out two active source seismic cruises by using JAMSTEC R/V Kairei in 2006. The wide-angle seismic data were acquired across the across-arc seamount chains (Nishi-shichito ridge) in KR0605 and along the across-arc seamount chain (Minami-Iojima ridge) in KR0601. In addition to those two wide-angle profiles, multichannel seismic data were also acquired along two profiles which are parallel to the strike of the across arc seamount chains. The wide-angle seismic data indicate thinning of crust toward the south across the Nishi-shichito ridge, and relatively flat and thin crust beneath the Minami-Ioujima ridge. The multichannel data show that the basement of the Shikoku basin can be traced beneath the western flank of the across-arc seamount chain. This suggest that a boundary between the Shikoku basin crust and the Oligocene Izu arc may be situated around the eastern end of the across-arc seamount chains.