East Java also decided to join Indonesia. East Java province borders the Java Sea in the north, the Strait of Bali in the east, the Indian Ocean in the south, as well as the Central Java province in the west. The length of the east-west stretch of about 400 km. The width of the stretch of the north-south in the west about 200 km, but in the eastern part of narrower by about 60 km. Madura is the largest island in East Java, separated from the mainland Java by the Strait of Madura. Bawean Island is located about 150 km north of
Ryukyu Trench gentle, reaching only 40-50° at 70 km depth. Ocean bottom seismography studies of the Ryukyu trench provide insight into the P-wave velocity structure of the area. In the northern part of the trench, several transects have been studied, including a profile of the back arc region parallel to the trench, a transect spanning the trench, fore arc and back arc region, and a transect spanning the Ryukyu volcanic arc. The transect perpendicular to the length of the trench images many distinct velocity layers. The sedimentary wedge created by subduction has four distinct layers with p-wave velocities of 1.8 km/s, 2.8-2.9