Permalink : http://hdl.handle.net/2115/44478

JaLCDOI : 10.14943/gbhu.73.239

Many dyke intrusion events have repeatedly occurred at Izu-Tobu Volcanoes since 1978．In order to evaluate volcanic activity of Izu-Tobu Volcanoes and to forecast the volcanic eruption，we investigate relationship between the amount of intrusive magma estimated from dyke parameters obtained by previous studies and the amount of volumetric strain change observed at Higashi-Izu．As a result，we find that there is an obvious correlation between the volume of dyke intrusions and the maximum amount of volumetric strain changes in 24 hours． In addition，we notice that large magma intrusion causes a remarkable seismic activity more than expected from the amount of volumetric strain changes． We propose a new technique for estimating the volume of dyke intrusion by using volumetric strain data observed at Higashi-Izu and introduce a new alert criteria based on the potential of volcanic eruption at Izu-Tobu Volcanoes．If our alert criteria is introduced，it is possible that volcanic warning is issued in an earlier stage of dyke intrusion event compared with the past．