Japan Geoscience Union Meeting 2019

Presentation information

[J] Poster

S (Solid Earth Sciences ) » S-VC Volcanology

[S-VC38] Active Volcanism

Mon. May 27, 2019 10:45 AM - 12:15 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Yuta Maeda(Nagoya University), Takahiro Miwa(National research institute for earth science and disaster prevention), Takeshi Nishimura(Department of Geophysics, Graduate School of Science, Tohoku University)

[SVC38-P33] Relationship between duration of eruption tremor and eruption volume

*Azusa Mori1, Hiroyuki Kumagai1 (1.Nagoya University Environmental Studies)

We studied the high-frequency seismic signals of eruption tremors during recent eruptions at various volcanoes and quantified their seismic source amplitudes (As) and cumulative source amplitudes (Is) in the 5–10 Hz based on the assumption of isotropic S-wave radiation. As and Is correspond to the maximum and the cumulative value of amplitudes at the source during eruption tremor. We previously found that the power law relations between As and Is holds for eruption tremors. We also found the proportional relation between eruption rate and As for eruption tremors by comparing seismic and geodetic data during sub-Plinian eruptions at Kirishima. In this study, we further investigated time variations of eruption tremors and found the scaling relation between duration of eruption tremor and eruption volume.

We calculated the envelope width (p) using the estimated values of As and Is and investigated the relation between p and Is. p is defined as Is/As and can be used as a parameter of duration (T) of a seismic envelope waveform (Kumagai et al., JGR, 2018). We found that p is proportional to 0.4 power of Is. We also found that envelope waveforms of eruption tremors in 5–10 Hz have the following features; the amplitudes of envelope waveforms gradually increase, remain roughly constant during a certain period, and gradually decrease to the noise level. Moreover, p tends to increase with As. These envelope waveforms can be approximated as trapezoids, where As and T correspond to their height and lower base, respectively. We found that the ratios of upper to lower bases for these envelope waveforms are roughly constant. In this case, the proportionality between p and T holds. Based on the relation between eruption rate and As, eruption volume (V) is proportional to Is. Therefore, the relation between p and Is as shown above indicates that T is proportional to 0.4 power of V. We found that this proportional relation is consistent with the estimates of T and V for various Plinian eruptions compiled by Mastin et al. (JVGR, 2009). This indicates that the scaling relation between duration of eruption tremor and eruption volume in Plinian eruptions holds over a wide range of eruption size.