The Sagami Trough also Sagami Trench, Sagami Megathrust, or Sagami Subduction Zone is a 340-kilometre (210 mi) long trough, which is the surface expression of the convergent plate boundary where the Philippine Sea plate is being subducted under the Okhotsk microplate. It stretches from the Boso triple junction in the east, where it meets the Japan Trench, to Sagami Bay in the west, where it meets the Nankai Trough. It runs north of the Izu Islands chain and the Izu–Bonin–Mariana Arc (IBM).