Dual Infrasound Sources from a Vulcanian Eruption of Sakurajima Volcano Inferred from Cross-Array Observation

Abstract

The study of volcano infrasound is becoming increasingly popular (Johnson and Ripepe, 2011; Fee and Matoza, 2013) with analysis of the recorded signals contributing to our understanding of eruption dynamics and enhancing capabilities in remote monitoring of volcanoes. Multiple studies have determined the source locations of the infrasound from volcanic eruptions. For example, Ripepe and Marchetti (2002) analyzed infrasound records for events occurring at Stromboli volcano. The authors successfully located different active vents in the craters to a horizontal resolution within a few tens of meters. Additionally, Jones and Johnson (2011) identified a migrating source of infrasound on the surface of the 200 m radius Santiaguito dome. Further from the vent region, infrasound signals are also generated by volcanic jet flow throughout the plume (Matoza et al. , 2009; Fee et al. , 2010). In these cases, large‐scale turbulent interactions within the volcanic plume are likely to be the source of infrasound waves. For these signals, the infrasound spectrum has a shape similar to that of man‐made turbulent jet noise (Tam et al. , 1996; Matoza et al. , 2009). It is plausible that infrasound waves recorded during volcanic eruptions are a composite signal generated by both processes at the vent/crater and within the eruption cloud itself. However, the source of infrasound is seldom constrained with sufficient spatial resolution to discriminate between signals at the vent or in the volcanic cloud. Determination of detailed infrasound source position and/or its time evolution during an eruption is a key research aim. In this paper, we investigate the locations of infrasound sources and reflections during vulcanian eruptions of Sakurajima volcano in Japan. Cyclic vulcanian eruptions and continuous open‐vent degassing characterize the recent activity of the Showa crater of Sakurajima volcano, which has been ongoing since June 2006 (Iguchi et al. , 2013). Total numbers of …