Permalink : http://hdl.handle.net/2115/38165

JaLCDOI : 10.14943/gbhu.72.363

We investigated a stress field around the magma chamber beneath Unzen Volcano, Kyushu, Japan, which erupted from 1990 until 1995, by using a stress-tensor inversion method. We used P wave polarity data of seismograms by earthquakes occurred during 1985-1999 for analysis. Our result clearly indicated that there were no changes in stress field during the period except for during 1986-1988. This suggested that the magma intrusion into shallower depths did not affect the stress field in this region. Clear change in stress field was observed during 1986-1988. This might be explained by applying the meshtexture crack model proposed by Hill (1977).