Earthquakes on the eastern margins of Asia (Japan, Kuril Islands, Philippines) are primarily caused by the subduction of the Pacific Plate beneath the Asian (Eurasian) Plate. As the heavy oceanic Pacific Plate sinks into the mantle, it creates a massive trench and builds intense pressure, which is released through frequent, high-magnitude earthquakes and volcanic activity. ANSWER: (C) Subduction of the Pacific Plate beneath the Asian Plate