Bandai volcano is one of active volcanoes in the southern part of the NE Japan. The Japan Metrological Agency made a new 100.6-m-deep borehole (JMA-V19) within the 1888 collapse crater of this volcano in 2009. I analyzed bulk chemical compositions of the core samples. This core consists of three units as follows: the Ura-Bandai-Kogen core lower unit (UBL; 100.6 to 72.8m in depth), the Ura-Bandai-Kogen core middle unit (UBM; 72.8 to 20.3m in depth) and the 1888 debris avalanche deposit (20.3 to 3.5m in depth), in ascending order. UBL is made up of andesite to dacite pyroclastic flow and debris flow deposits, showing a distal volcanic fan facies. UBM is composed of a basal basaltic andesite lava flow and overlying andesite lava flows, showing a proximal volcanic cone facies. Geochemical features of UBL are well reconciled with the calc-alkalic rocks corresponding to the medium-K series of Nekoma volcano, which is older than Bandai volcano. On the other hand, UBM is made up of unique tholeiitic rocks, although the superficial products of Bandai volcano (Akahani-Kushigamine, Kobandai and Obandai edifices) consist solery of calc-alkalic andesite. UBM is regarded as concealed initial products of Bandai volcano. ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd ratios for the basal basaltic andesite in UBM are 0.70406 and 0.51282, respectively. These values are further depleted than those of the younger edifices of Bandai volcanoes and other frontal volcanoes in the southern part of NE Japan, and manifest the beginning of Bandai volcano. Trace element variations of the subsequent tholeiitic andesite samples in UBM show that the tholeiitic andesite was not derived from the initial basaltic andesite, but was generated by a partial melting of a crustal material. Such geochemical change presumably implies temperature-increasing processes caused by intrusion of depleted melt from the mantle into the lower crust.

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Shallow seismic reflection structure down to 2km b.s. 1. in Sakurajima Volcano is presented with an application of Pseudo-Reflection profiling. Data used in this study are obtained through a controlled source seismic experiment, the 2008 Sakurajima project. Two final profiles are obtained after the processing for the lines NS and EW. Prominent reflective horizons can be recognized in shallow part of the both profiles. Complicated pattern of the reflection horizons is correlated as a cross section of piled-up lava flows. Thicknesses of the historical lava flows are recognized and some unknown lava flows are also detected in both profiles. However, less reflective zone appear in 100 to 800m b.s. 1. in the profile. The less reflective zone is inferred as pyroclastic materials from underwater eruptions because the zone corresponds to the low resistive layer in the resistivity profile. These results can be contributed to discuss evolution history and explosion mechanisms.

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