Discontinuities such as onlap, toplap and downlap terminations, are important key structures in seismic stratigraphy. These patterns characterize the Plio-Pleistocene Kakegawa Group in Shizuoka, the middle Pleistocene Kasamori Formation in Chiba, and the Plio-Pleistocene Uonuma Group in Niigata. The patterns within these successions can be detected by tracing intercalated pyroclastic layers (tephra beds), which provide the same information as the synchronous reflection lines in seismic data. These patterns, therefore, allow the stratigraphic sequence to be divided into forearc and backarc basin-fill successions. The depositional sequences of the Kakegawa and Uonuma groups are third-order, ranging from ca. 2.6 Ma to 1.0 Ma. The Kasamori Formation has high-frequency sequences dating from 0.60 Ma to 0.45 Ma. All these sequences are believed to have been produced by glacio-eustatic sea-level changes.