摘要：The convergent plate boundaries known as the subduction zone is the location where the cold, hydrate, and old oceanic plate subduct under the hot, dry, and young continental plate. The top of the oceanic plate, i.e. the oceanic crust usually is less than 6 km thick carries the hydrate material to the hot continental mantle, which is commonly an indication of the occurrence of the deep earthquake. From the recent studies, the deep regional earthquake body wave signal that occurred at the subduction zone was found dispersed and or shown as a waveguide. Thus, by examining these signals, we could further estimate the body wave characteristics at the subduction zone. A narrow bandpass signal and the maximum of Hilbert transform envelope are being used to estimate the delay time of the dominant frequency energy at the Southern Ryukyus subduction zone. It was found that the Southern Ryukyus has a larger delay with the dominant frequency at 2 Hz, thus, the signal travel within the oceanic crust where it acts as a low-velocity layer compared to the surrounding continental and oceanic mantle, inversely it is known as a high-quality material (preserve the high-frequency energy).
