Magnetic Anomaly Characteristics in the Middle Okinawa Trough

Itis shown from the magnetic anomaly data thatthe shelf depression zone is characteristic of de- creasing negative magnetic anomalies,and the shelf edge folded belt is characteristic of jump- increasing positive anomalies;the Okinawa Trough area shows 2 types of magnetic anomalies,its west slop area is characteristic of gentle negative magnetic anomalies,and its through area is characteristic of increasing magnetic anomalies with high frequency fluctuation.The Ryukyu Island arc area is characteristic of gently decreasing negative magnetic anomalies,butthe island arc area near the Okinawa Trough is characteristic of high frequency increasing positive magnetic anomalies.The magnetic anomalies in these tectonic belts show significantly banded distributions,the magnetic anomalies in the southern survey area( near2 7°40′ N,1 2 7°0 0′ E) show obviously banded feature and are well consistent with the bottom topography,which indicates thatthe middle Okinawa Trough has entered a spreading stage.