水準測量によって測定された桜島火山の地盤上下変動 --2014年11月測量の結果--

Abstract

We conducted the precise leveling survey in Sakurajima volcano in November 2014, in order to evaluate the vertical ground deformation associated with the recent eruptive activity. The measured survey data are compared with those of the previous survey, resulting in the relative vertical displacements during the period from November 2013 to November 2014. The results show that no remarkable vertical displacements are seen at bench marks around the northern part of Sakurajima, where the ground uplifts have been observed since around 1993. It is suggested that the magma storage at the magma reservoir beneath Aira caldera is less progressing. The resultant displacements also indicate the ground subsidence near the central part of this volcano, reflecting the deflation of the magma reservoir located beneath Minamidake (or Showa) crater, caused by the recent increase of the volume of ejected magma associated with the eruptive activity at Showa crater.