JMA reported an increase in the amplitude of volcanic tremor at Asosan on 14 April, increasing the possibility of an eruption at Nakadake Crater.
The Alert Level was raised to 2 (on a scale of 1-5).
Tremor amplitude further increased on 15 April.
A very small eruption was recorded at 1828 on 16 April, producing a plume that rose 200 m above the crater rim and drifted NW.
Source: Japan Meteorological Agency (JMA)