S-wave modeling of the Showa-Shinzan lava dome in Usu Volcano, Northern Japan, from seismic observations

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1093/gji/ggac111. This is version 2 of this Preprint.

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Authors

Akiko Takeo, Kiwamu Nishida, Hiroshi Aoyama, Motoko Ishise, Takeru Kai, Ryo Kurihara, Takuto Maeda, Yuta Mizutani, Yuki Nakashima, Shogo Nagahara, Xiaowen Wang, Lingling Ye, Takeshi Akuhara , Yosuke Aoki

Abstract

To obtain an internal S-wave velocity structure, we conducted a passive seismic campaign with 21 1-Hz seismometers on and around the Showa-Shinzan lava dome, which emerged during the 1943–1945 eruption of Usu Volcano, Japan. Before the campaign, we calibrated seismometers and found slight phase-response differences between seismometers of less than 1–2 degrees. After the campaign, we extracted seismic wavefield by taking cross-correlations of vertical-component ambient noise records between seismic sites. We developed a new method to measure phase velocities of the Rayleigh wave automatically by assuming layered structure and finally obtained one-dimensional S-wave velocity models in summit, roof and base regions. The obtained S-wave velocity right beneath the intruded lava dome is higher than that in surrounding areas by a few tens of percent down to a few hundred meters below sea level, indicating narrow but deep existence of the root of the lava dome. The obtained S-wave velocity at depths shallower than ~50 m inside the lava dome in the summit area was ~1 km/s, significantly lower than that predicted from the density of ~2.3 x 10^3 kg/m estimated in previous muon-radiography studies and a conventional scaling, indicating the effect of cracking in the lava dome.

DOI

https://doi.org/10.31223/X5GW5M

Subjects

Geophysics and Seismology, Tectonics and Structure, Volcanology

Keywords

Seismology, volcanology, Seismic interferometry

Dates

Published: 2022-02-09 01:36

Last Updated: 2022-03-22 10:40

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License

CC BY Attribution 4.0 International

Additional Metadata

Data Availability (Reason not available):
Cross-correlation functions taken from the obtained seismic data are uploaded at the Zenodo repository (doi:10.5281/zenodo.4313960).