| Summary: | application/pdf 富山トラフ以東の日本海東縁の大陸斜面と陸上の瑞穂摺曲帯よりなる日本海東縁変動帯は北米・ユーラシア両プレート間の1～2Ma前以降の収束(力学)境界域であるという考えが説明される.日本海盆東縁と富山トラフ内に点在する凹地を連ねた地帯は沈み込みを示唆する構造を伴うので新生の海溝である可能性がある. Along the eastern Japan Sea there lies a zone of active contractional deformation as seen in higher seismicity, young submarine tectonic relief and deformed Quaternary strata. The zone comprises the coastal regions and continental slopes of Northeast Japan. The recently proposed idea that this east Japan Sea deformation zone represents a nascent convergent zone since 1～2Ma by between North American and Eurasian plates is reviewed. It seems highly possible that the six isolated topographic depressions and associated minor shallow valleys on the eastern edge of the deep basin floor of the Japan Sea constitute a surface manifestation of the nascent trench where the young lithosphere of the Japan Sea has just started to subduct westwards beneath northeast Japan. This supposed convergent plate boundary extends northwards and connects somehow to the mid-Arctic ridge and southwards through Fossa Magna, a colliding sector, to Suruga Bay forming another triple junction near Volcano Fuji where the three convergent boundaries between Eurasian, North American and Philippine Sea plates meet. departmental bulletin paper
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