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[SVC28-15] Temporal variation of b value of volcanic earthquakes associated with the 2008-2011 Shinmoe-dake eruption
Keywords:b value, volcanic earthquake, volcanic eruption
The latest eruptive activity of Shinmoe-dake started on August 22, 2008 after 16 years dormancy. Subsequently, it erupted on March 30, April 17, May 27, June 27 and 28, and July 5 and 10, 2010. In 2011, the eruption started on January 19 and was followed by sub-Plinian eruption on 27 January. Eruptive activity gradually ceased since February 2 and moved to Vulcanian activities. It erupted in October 2017 and in March 2018. Eruptions continued until June 27. In this study, we investigate the change in b value for the seismic activity from just before the 2008 eruption to the 2011 eruption and estimate the temporal change in the properties of the region just below the summit crater.
Seismic activity around Shinmoe-dake is low before the 22 August eruption, where a seismic swarm continued since 3 days before the eruption. After the eruption, seismic activity became low, but the activity became higher again in December 2009 and continued until the January 2011 eruption. The figure shows the frequency-magnitude distribution of the earthquakes. The horizontal axis indicates the magnitudes (M) of earthquakes and the vertical axis is the cumulative number of earthquakes larger than M. Solid diamonds represent the seismic swarm before the 2008 eruption. Solid squares represent the seismic activity from just after the eruption to December 2008. Solid triangles show the seismic activity from January 2009 to just before the 2011 eruption. We applied the Gutenberg-Richter’s relation to the data to find b values for each period. The result is as follows: 2.0 just before the 2008 eruption, 0.9 after the eruption until December 2008 and 0.6 after that. This indicates that the volcanic activity field just below the summit crater is significantly different in nature from just before the 2008 eruption and after that. This indicates that the volcanic activity field just below the summit crater is significantly different in nature from just before the 2008 eruption and after that. For example, this difference can be interpreted as the activity to create a passage for volcanic fluid occurred immediately before the eruption, and then the activity occurred in the situation where the passage already existed.
Seismic activity around Shinmoe-dake is low before the 22 August eruption, where a seismic swarm continued since 3 days before the eruption. After the eruption, seismic activity became low, but the activity became higher again in December 2009 and continued until the January 2011 eruption. The figure shows the frequency-magnitude distribution of the earthquakes. The horizontal axis indicates the magnitudes (M) of earthquakes and the vertical axis is the cumulative number of earthquakes larger than M. Solid diamonds represent the seismic swarm before the 2008 eruption. Solid squares represent the seismic activity from just after the eruption to December 2008. Solid triangles show the seismic activity from January 2009 to just before the 2011 eruption. We applied the Gutenberg-Richter’s relation to the data to find b values for each period. The result is as follows: 2.0 just before the 2008 eruption, 0.9 after the eruption until December 2008 and 0.6 after that. This indicates that the volcanic activity field just below the summit crater is significantly different in nature from just before the 2008 eruption and after that. This indicates that the volcanic activity field just below the summit crater is significantly different in nature from just before the 2008 eruption and after that. For example, this difference can be interpreted as the activity to create a passage for volcanic fluid occurred immediately before the eruption, and then the activity occurred in the situation where the passage already existed.