Earthquake Characteristics before Eruptions of Japan’s Ontake Volcano in 2007 and 2014

Abstract:

Recent two phreatic eruptions occurred at Japan’s Ontake volcano on September 27, 2014 and in late March 2007. In this presentation, we analyze and compare seismicity and earthquake characteristics before eruptions of 2007 and 2014 and investigate possible precursory information of the two eruptions. We detect earthquakes associated with Japan’s Ontake eruptions in 2007 and 2014 using the match-and-locate (M&L) method. 37 times more events than the Japan Meteorological Agency (JMA) catalog and 30 times more events than the JMA catalog are detected during eruptions of 2007 and 2014, respectively. The detected earthquakes are further classified into three different types based on their spectrum characteristics: long-period (LP) events, LP-associated events and volcano-tectonic (VT) earthquakes. Both LP and LP-associated events are observed in two eruptions. We suggest that the observed intense seismicity before the two eruptions indicates the rewaking of Ontake volcano and might be used to predict its impending eruption in long-term, the temporal persistence and spatial concentration of LP and LP-associated events may be used to predict the eventual eruption location of Ontake volcano, and the maximum magnitude of the LP events may be used as an indicator of its eruption magnitude.