Data obtained from the Shinjima Seismic observation well

Table S1. Refractive index values of orthopyroxene and volcanic glass from the Shinjima Seismic Observation Well and the values reported for key tephras in the inner area of Kagoshima Bay.

Table S2. XRF analyses of the pumice and lithic clasts of the Susaki Pumice, Shinjima Pumice, and unnamed tephras from the drill cores of the Shinjima Seismic Observation Well.

Table S3. Diatom fossils identified in the drill cores of the Shinjima Seismic Observation Well.

Table S4. Accumulation rates of post-caldera sediment in the Shinjima Seismic Observation Well.

Fig. S1. History of stratigraphic division of the sedimentary succession exposed on Shinjima Island .

Fig. S2. Photographs showing the mode of occurrence of Facies PLT. Inverse grading of pumice lapilli is likely a diagnostic feature of subaqueous eruption-fed density current deposits. The main part of the facies is overlain in part by normally graded ash and laminated fine ash, suggesting a transition to volcaniclastic turbidites by the ingestion of ambient water during the flowage.

Fig. S3. Photographs showing the mode of occurrence of Facies GPLT.

Fig. S4. Photomicrographs showing the mode of occurrence of pumice and dense rock clasts in drill cores of Facies GPLT collected at depths of 318–319 m in the Shinjima Seismic Observation Well.