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Triplicated P waveforms related to the 410-km discontinuity from five intermediate-depth earthquakes in the central Philippines are clearly recorded by the Chinese Digital Seismic Network, but some branches of the S-wave triplications are obscure. Matching the observed P-wave triplications with synthetics through a grid-search technique, we obtain the best-fit 1D P-wave velocity model near the 410-km discontinuity beneath the northeastern South China Sea. In such a model, a low-velocity layer (LVL) is found to reside atop the mantle transition zone, and it is characterized by a thickness of 92.5 +/- 11.5 km and a P-wave velocity decrement of 1.5% +/- 0.1% compared with the IASP91 model. The relatively thick and weak LVL is possibly a response of a small amount of remnant hydrous partial melts after plume-like upwelling.