Sumatra Trench Sumatra Trench The Sumatra Trench belongs to the Sunda Trench or Java Trench. The Sunda subduction zone (called also: the Sumatra-Andaman subduction zone) is located in the east part of Indian Ocean, and is about 300 km from the southwest coast of Sumatra and Java islands. It extends over 5000 km long, starting from Burma in the northwest and ending at Sumba Island in the southeast. The Java trench was generated by the oblique subduction of the Indo-Australian Plate into the Sunda plate at a rate of 61mm/y (in the south) and 51mm/y (in the north). The oceanic crust being
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