Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

S (Solid Earth Sciences) » S-VC Volcanology

[S-VC41] Active Volcanism

Mon. May 21, 2018 3:30 PM - 5:00 PM Convention Hall A (CH-A) (2F International Conference Hall, Makuhari Messe)

convener:Yuta Maeda(Nagoya University), Takahiro Miwa(National research institute for earth science and disaster prevention), Yosuke Aoki(東京大学地震研究所, 共同), Takeshi Nishimura(Department of Geophysics, Graduate School of Science, Tohoku University), Takahiro Ohkura(Aso Volcanological Laboratory, Institute for Geothermal Sciences, Graduate School of Science, Kyoto University), Satoshi Okumura(Division of Earth and Planetary Materials Science, Department of Earth Science, Graduate School of Science, Tohoku University), Tomofumi Kozono(Department of Geophysics, Graduate School of Science, Tohoku University), Chairperson:Ohkura Takahiro, Yokoo Akihiko

4:00 PM - 4:15 PM

[SVC41-09] Observations of diverse long-period tremors at Aso Volcano, Japan

Jieming Niu1, *Teh-Ru Alex Song1 (1.Seismological Laboratory, Department of Earth Sciences, University College London)

Keywords:Aso volcano, diverse Long-period tremor (DLPT), DLPT catalog, Strombolian eruptions

Long-period tremors (LPTs) are frequently observed and documented at Aso volcano since the pioneering work by Sassa (1935). Previous efforts (e.g., Kaneshima et al., 1996; Kawakatsu et al., 2000) have characterized LPTs as repetitive and isolated events, with a resonance period of ~15 seconds and a duration of several tens of seconds. Since the initial waveform polarity of LPTs is typically negative, depressurization or/and degassing is commonly invoked as the triggering mechanism. However, it is also documented that, occasionally, especially during phreatic eruptions, the initial waveform polarity of LPTs is positive, suggesting a triggering mechanism linked to magmatic heating and vaporization in the hydrothermal reservoir. Since these diverse LPTs (DLPTs) have not been systematically investigated, especially during the active period, we attempt to characterise how DLPTs of different waveform shape, polarity, or/and resonance frequency vary between 2011 and 2016, during which Aso volcano became very active with frequent phreatic eruptions, intermittent Strombolian eruptions as well as occasional phreatomagmatic eruptions.

To explore DLPTs at Aso volcano, we carry out systematic analysis of continuous data at V-net and Japan Meterogeolgical Agency (JMA) volcanic seismic network. After visually inspect LPT waveform across the networks, we devise a two-stage process to construct a catalog for DLPTs. Using the LPT waveform as a template, the first stage involves continuous wavelet transformation to search for LPTs with spectra features comparable to that of the template. Through waveform cross-correlation and stacking, we identify at least 2 types of LPTs with identical waveform shapes but opposite polarities. In the second stage, we use these identified LPTs as templates and apply match filter algorithm to conduct an extensive search.

In this presentation, we will present the DLPTs catalog, consist of ~ 200,000 events between 2011 and 2016. We will focus on similarities and differences among DLPTs and how their activities change over the 6 year period. In the subsequent presentation, Song and Niu (2018, this meeting) will detail how the DLPTs may provide a clue to possible deformation in the deep conduit or/and magma chamber.