Bending-Related Topographic Structures of the Subducting Plate in the Northwestern Pacific Ocean - Accretionary Prisms and Convergent Margin Tectonics in the Northwest Pacific Basin - page 31

145°00'E 145°30'E 146°00'E 146°30'E

38°00'N 38°00'N

1000 nT

37°30'N 37°30'N

37°00'N 37°00'N

36°30'N 36°30'N

36°00'N 36°00'N

145°00'E 145°30'E 146°00'E 146°30'E

Fig. 22 Along-track magnetic anomaly profiles east of the Joban Seamounts. Conventions are
identical to Fig. 21

reveals a discontinuity of lineations between M15 and M12 east of the Kashima
Fracture Zone (Fig. 22 ). The discontinuity can be traced northeastward to lineation
M11. The offsets of the magnetic anomaly lineations have a trend different from
fracture zones in this study area. This evidence implies that the discontinuity is due
to a northeastward propagating spreading ridge.
Nakanishi et al. ( 1989 ) identified lineations from M11 to M3 between the
Kashima Fracture Zone and the Izu-Ogasawara Trench, which have a strike a little
different from those east of the Kashima Fracture Zone. The detailed examination
of magnetic anomalies in the study area could not confirm their identification in
spite of the increase of cruise data. Magnetic lineations younger than M7 were
missed in this area.