5:15 PM - 6:30 PM
[SVC47-P10] Temporal change of SO2 discharge at Asama volcano
Keywords:Asama volcano, SO2, seismic waveform, volcanic fume
A positive correlation between frequency of BL-type volcanic earthquake and SO2 discharge is confirmed during the 2015 eruption period; that between volcanic fume index and SO2 discharge is in a similar way. The similar correlations are recognized during the eruption periods in 2008 and 2009. On the other hand, we can’t make certain of correlations between frequencies of BL-type event and volcanic fume indexes during the eruption periods in 2003 and 2004; we frequently observed increments of SO2 emission without increase of BL-type earthquakes and volcanic fumes. (fig.1) A very long-period pulse, hereafter we call it VLP, is an impulsive motion with a dominant period longer than 5 seconds accompanied by a tilt change, which is excited by a sudden gas emission (Maeda and Takeo, 2012). Weak correlations are confirmed between the frequencies of VLP and BL-type event, and between the frequency of VLP and SO2 discharge. However, there are several examples of large amount of SO2 emission with a few occurrence of VLP. During non-eruption periods, the daily SO2 discharge rate could not exceed 2000 ton/day even though the increment of BL-type activity.
The increment of SO2 emission seems to be plausible data indicating a volcanic eruption potential, and the positive correlations among SO2 emission, volcanic fume, and daily frequency of volcanic event are confirmed during the 2008, 2009, and 2015 eruption periods. However, there are some observations that SO2 emission represented weak correlations with the frequencies of BL-type event and with the volcanic fume indexes even though the eruption periods (2003 and 2004). The gas emission system seems to fluctuate along the volcanic activity.