- © 2014 by the Seismological Society of America
Online Material: Figures showing normalized onset peak pressure and energy across the Sakurajima network.
Great diversity has been observed in volcanic infrasound signals worldwide, reflecting rich variability in their physical source mechanisms. Infrasound waveforms, estimated signal powers, and frequency contents vary dramatically across a large spectrum of physical eruptive styles (e.g., Johnson and Ripepe, 2011; Fee and Matoza, 2013; Garces et al., 2013). The observed infrasound signals and eruptive styles span, but do not fall neatly into, the idealized terms such as Hawaiian, Strombolian, Vulcanian, sub‐Plinian, and Plinian (e.g., Walker, 1973; Fee and Matoza, 2013). In physical volcanology, the description and classification of explosive eruption styles are traditionally based on metrics of the thickness, areal extent, and grain size distributions of eruptive products (Walker, 1973). However, eruptive products represent time‐integrated end results of the fragmentation, ejection, and dispersal processes, and the idealized terms do not adequately capture the observed diversity in explosion styles. Infrasound data, which represent a geophysical recording of the explosion process, show promise for better characterizing, quantifying, and classifying the many varied mechanisms and styles of explosive eruptions (e.g., Johnson, 2007; Sahetapy‐Engel et al., 2008; Marchetti et al., 2009; Lopez et al., 2013).
Previous conceptual understanding of acoustic signals from explosive eruptions has tended to focus on two end‐member signal durations: (1) discrete explosion (blast) waves with relatively simple waveforms lasting from several to tens of seconds (e.g., Firstov and Kravchenko, 1996; Ripepe and Marchetti, 2002; Johnson, 2003; Marchetti et al., 2009, 2013) and (2) sustained, broadband, infrasonic tremor signals lasting from minutes to hours (e.g., Vergniolle and Caplan‐Auerbach, 2006; Matoza et al., 2009; Fee, Steffke, …