The yellow line is the Suruga Trough, part of the longer Nankai Trough in red.
The Suruga Trough (駿河トラフ, Suruga Torafu) is a trough that lies off the coast of Suruga Bay in Japan, forming part of the Nankai Trough, the latter being responsible the source of many large earthquakes in Japan's history. Both mark the boundary of the Philippine Sea Platesubducting under the Amurian Plate.
