On 8 October 2023 (UTC), unique earthquakes occurred in the Izu-Ogasawara Arc, Japan, in which the P- and S-phases were barely visible and only the T-phases were evident, followed by tsunamis that reached islands in the Izu-Ogasawara Arc and a wide area of the Pacific coast of southwest Japan. Our estimated T-phase source area coincides with the Sofu Seamount, which was previously unrecognized as an active submarine volcano. A bathymetric survey of the seamount conducted 1 month after the event revealed characteristics of the seamount with a caldera and a central cone. Compared to the bathymetry in 1987, the topography in the caldera had changed significantly such as a crater forming in the central cone. This seamount is likely to be an active volcano. The topographic changes on the caldera-sized scale that occurred at the caldera can be explained as a source of the October tsunami.

中文翻译：

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位于日本 2023 年 10 月地震和海啸源区的捫生海山海底火山


2023 年 10 月 8 日（UTC），日本伊豆小笠原弧发生了独特的地震，其中 P 期和 S 期几乎不可见，只有 T 期很明显，随后海啸到达了伊豆小笠原弧的岛屿和日本西南部太平洋沿岸的广大地区。我们估计的 T 期源区与捣腐海山重合，捣腐海山以前不被认为是活的海底火山。事件发生 1 个月后对海山进行的测深调查揭示了具有破火山口和中央圆锥体的海山特征。与 1987 年的测深相比，破火山口的地形发生了显着变化，例如在中央圆锥体中形成陨石坑。这座海山很可能是一座活火山。在火山口发生的破火山口大小尺度的地形变化可以解释为 10 月海啸的来源。