Seismic and infrasonic eruption tremors and their relation to magma discharge rate: A case study for sub‐Plinian events in the 2011 eruption of Shinmoe‐dake, Japan

Abstract

AbstractMagma discharge rate is one of the most important parameters in quantifying volcanic activity. Many previous works have attempted to connect observations of seismic and infrasonic eruption tremors with magma discharge rate. Power law scaling relations with different power indices have been proposed based on various data sets and models. The 2011 eruption of Shinmoe‐dake, Japan, provides an excellent data set with which to investigate these relationships for a sustained explosive eruption sequence. Magma discharge rates are well constrained by geodetic, geologic, and remote sensing methods. Seismic and infrasonic data were recorded close to the vent. Moreover, contributions to ground shaking from infrasound can be distinguished from seismic signals in the seismometer records. As a result, linear power law relationships are found to fit all pairs of variables (seismic eruption tremor power, infrasonic eruption tremor power, and magma discharge rate) in the quasi‐stable or slowly growing stages of the sub‐Plinian events. Similar relations have been reported for other eruptions but only between seismic eruption tremors and magma discharge rate or between seismic and infrasonic eruption tremors. Existing models do not fully explain the observed relationships. The possibility is proposed that Plinian‐type eruptions generate both seismic and infrasonic eruption tremors by successive explosions at the fragmentation surface in the conduit; these linear relationships can therefore be observed only under conditions where flow and fragmentation in the conduit are stable.