水準測量によって測定された桜島火山周辺域の地盤上下変動 -2012年11月および12月測量の結果-

Abstract

We conducted the precise leveling survey in and around Sakurajima volcano in November and December 2012. The survey data measured in Sakurajima are compared with those of the previous survey, resulting in the relative vertical displacements during the period from November 2011 to November-December 2012. The resultant displacements indicate the ground uplift at bench marks around the northern part of Sakurajima. From the analysis based on a spherical source model, the inflation source is located at 9.6 km depth beneath the center of Aira caldera. The relative vertical displacements around the western coast of Kagoshima Bay calculated during the period from November 2009 (the previous survey) to November 2012 also show the ground uplift near the center of Aira caldera. These results suggest that the magma storage at the magma reservoir beneath Aira caldera is progressing in spite of the recent increase of the volume of ejected magma associated with the eruptive activity at Showa crater.