研究者詳細 - 前田　裕太

論文 - 前田　裕太

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A numerical model for precursory time sequences of the phreatic eruptions of Mt. Ontake, central Japan 査読有り

Yuta Maeda

Earth, Planets and Space 76 巻頁： 63 2024年5月

Solidified magma reservoir derived from active source seismic experiments in the Aira caldera, southern Kyushu, Japan 査読有り

Hiroki Miyamachi, Hiroshi Yakiwara, Reiji Kobayashi, Shuichiro Hirano, Takeshi Kubo, Masakazu Souda, Kenyu Sakao, Naohiro Unno, Takeshi Matsushima, Kazunari Uchida, Rintaro Miyamachi, Kenshin Isoda, Yoshiko Teguri, Yoshinosuke Kamiya, Agnis Triahadini, Hiroshi Shimizu, Hiroshi Katao, Takuo Shibutani, Takeshi Tameguri, Yusuke Yamashita, Tsutomu Miura, Jun Nakagawa, Itaru Yoneda, Shinya Kato, Kosei Takishita, Kazuho Nakai, Yuta Maeda, Toshiki Watanabe, Shinichiro Horikawa, Kenjiro Matsushiro, Takashi Okuda, Shuhei Tsuji, Naoki Sogawa, Daima Hasegawa, Kazuo Nakahigashi, Eiji Kurashimo, Tomoaki Yamada, Hideji Abe, Miwako Ando, Shinichi Tanaka, Satoshi Ikezawa, Takaya Iwasaki, Masanao Shinohara, Toshinori Sato, Mare Yamamoto, Ryosuke Azuma, Satoshi Hirahara, Takashi Nakayama, Syuichi Suzuki, Shuhei Otomo, Ryota Hino, Tomoki Tsutsui, Yusuke Inoue, Ryuichi Takei, Yuya Tada, Hiroaki Takahashi, Yoshio Murai, Hiroshi Aoyama, Mako Ohzono, Takahiro Shiina, Masamitsu Takada, Masayoshi Ichiyanagi, Teruhiro Yamaguchi, Natsuki Ono, Kazuma Saito, Chihiro Ito, Yuuki Susukida, Tatsuya Nakagaki, Yasuhisa Tanaka, Yasuhiko Akinaga

Earth, Planets and Space 75 巻頁： 166 2023年10月

Seismic structure and its implication on the hydrothermal system beneath Mt. Ontake, central Japan 査読有り

Yuta Maeda, Toshiki Watanabe

Earth, Planets and Space 75 巻頁： 115 2023年7月

A systematic survey for precursory tilt changes at all monitored eruptions in Japan 査読有り

Yuta Maeda

Journal of Volcanology and Geothermal Research 439 巻頁： 107831 2023年6月

Waveform inversion of the ultra-long-period seismic event associated with ground tilt motion during an eruption of Mount Kusatsu–Shirane, Japan, on January 23, 2018 査読有り

Ryohei Takahashi, Yuta Maeda, Toshiki Watanabe

Earth, Planets and Space 74 巻頁： 85 2022年6月

Estimating errors in autocorrelation functions for reliable investigations of reflection profiles 査読有り

Yuta Maeda, Toshiki Watanabe

Earth, Planets and Space 74 巻頁： 48 2022年3月

Machine learning based detection of volcano seismicity using the spatial pattern of amplitudes 査読有り

Yuta Maeda, Yoshiko Yamanaka, Takeo Ito, Shinichiro Horikawa

Geophysical Journal International 225 巻 ( 1 ) 頁： 416 - 444 2020年12月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

We propose a new algorithm, focusing on spatial amplitude patterns, to automatically detect volcano seismic events from continuous waveforms. Candidate seismic events are detected based on signal-to-noise ratios. The algorithm then utilizes supervised machine learning to classify the existing candidate events into true and false categories. The input learning data are the ratios of the number of time samples with amplitudes greater than the background noise level at 1 s intervals (large amplitude ratios) given at every station site, and a manual classification table in which `true'' or `false'' flags are assigned to candidate events. A two-step approach is implemented in our procedure. First, using the large amplitude ratios at all stations, a neural network model representing a continuous spatial distribution of large amplitude probabilities is investigated at 1 s intervals. Second, several features are extracted from these spatial distributions, and a relation between the features and classification to true and false events is learned by a support vector machine. This two-step approach is essential to account for temporal loss of data, or station installation, movement, or removal. We evaluated the algorithm using data from Mt. Ontake, Japan, during the first ten days of a dense observation trial in the summit region (November 1–10, 2017). Results showed a classification accuracy of more than 97 per cent.

DOI： 10.1093/gji/ggaa593

その他リンク： https://nagoya.repo.nii.ac.jp/records/2001674

Scattering and attenuation characteristics at volcanoes inferred from envelope widths of natural and active seismic sources 査読有り国際共著

Hiroyuki Kumagai, Roberto Torres, Yuta Maeda

Journal of Geophysical Research: Solid Earth 125 巻 ( 11 ) 頁： e2020JB020249 2020年11月

Empirical formula for the quality factors of crack resonances and its application to the estimation of source properties of long-period seismic events at active volcanoes 査読有り国際共著

Kimiko Taguchi, Hiroyuki Kumagai, Yuta Maeda, Roberto Torres

Geophysical Journal International 224 巻 ( 3 ) 頁： 2131-2148 2020年10月

2016年熊本地震合同地震観測データ ──地震学的解析の基礎的資料として── 査読有り

志藤あずさ, 光岡郁穂, 松本聡, 松島健, 相澤広記, 清水洋, 内田和也, 神薗めぐみ, 手操佳子, 中元真美, 宮町凛太郎, 一柳昌義, 大園真子, 岡田和見, 勝俣啓, 高田真秀, 高橋浩晃, 谷岡勇郎, 山口照寛, 小菅正裕, 東龍介, 内田直希, 江本賢太郎, 太田雄策, 岡田知己, 海田俊輝, 小園誠史, 鈴木秀市, 高木涼太, 出町知嗣, 中原恒, 中山貴史, 平原聡, 松澤暢, 三浦哲, 山本希, 今西和俊, 内出崇彦, 吉見雅行, 青井真, 浅野陽一, 上野友岳, 藤田英輔, 阿部英二, 飯高隆, 岩崎貴哉, 加藤愛太郎, 蔵下英司, 酒井慎一, 椎名高裕, 芹澤正人, 田中伸一, 中川茂樹, 平田直, 増田正孝, 宮川幸治, 八木健夫, 渡邉篤志, 後藤和彦, 伊藤武男, 奥田隆, 寺川寿子, 堀川信一郎, 前田裕太, 松廣健二郎, 山中佳子, 渡辺俊樹, 飯尾能久, 片尾浩, 加納靖之, 津田寛大, 三浦勉, 村本智也, 山下裕亮, 大久保慎人, 山品匡史, 大倉敬宏, 中尾茂, 平野舟一郎, 宮町宏樹, 八木原寛

地震 73 巻頁： 149 - 157 2020年10月

Amplitude source location method with depth-dependent scattering and attenuation structures: Application at Nevado del Ruiz volcano, Colombia 査読有り国際共著

Hiroyuki Kumagai John Makario Londoño Yuta Maeda Alvaro Esteban Acevedo Rivas

Journal of Geophysical Research: Solid Earth 124 巻 ( 11 ) 頁： 11585-11600 2019年12月

Comparison of high- and low-frequency signal sources for very-long-period seismic events at Asama volcano, Japan 査読有り

Yuta Maeda, Minoru Takeo, Ryunosuke Kazahaya

Geophysical Journal International 217 巻 ( 1 ) 頁： 389 - 404 2019年1月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Very-long-period (VLP) seismic events at Asama volcano in central Japan are characterized by a transient signal of 10-20 s duration. Associated with the transient motion, a high-frequency (HF) oscillation within the 5-10 Hz band is observed. We investigated the location and size of the oscillation source in the HF band (HF source) using an amplitude source location method and compared our results with those for the VLP band (VLP source) deduced in our previous waveform inversion study. We analysed 1437 VLP events recorded during an intense observation campaign during 2008-2009, and additional 571 events surrounding an eruptive activity in 2015 (including a VLP event that immediately preceded an eruption). The HF source locations of most events were deeper than the VLP source locations by ~150 m, although there was almost no time lag between the signals. This suggests a strong connection between the two sources, with one source immediately responding to the other. The eruptive VLP event had an HF source location close to normal VLP events but had a greater event size. We surmise that the HF signal is caused by an inflow of volcanic gas from depth into a semi-vertical crack-like cavity (as imaged in our previous waveform inversion study), and the VLP signal is caused by resultant inflation of the same cavity. The centroid of inflation (VLP source) is near the roof of the cavity, where gas accumulates, whereas the HF oscillation is emitted more intensely from lower and narrower portions of the cavity. This results in source depth differences between the two signal bands. In this model, the inflation rate of the cavity is controlled by the volume flux of the gas inflow, producing similar temporal variations between the VLP and HF signals. According to this model, the eruptive VLP is associated with a greater amount of gas inflow and accumulation, which likely played a key role in the eruption.

DOI： 10.1093/gji/ggz021

その他リンク： https://nagoya.repo.nii.ac.jp/records/28498

Envelope widths of volcano-seismic events and seismic scattering characteristics beneath volcanoes 査読有り国際共著

Hiroyuki Kumagai, John Makario Londoño, Yuta Maeda, Cristian Mauricio López Velez, Rudy Lacson Jr

Journal of Geophysical Research: Solid Earth 123 巻 ( 11 ) 頁： 9764 - 9777 2018年10月

Source properties and triggering processes of long-period events beneath volcanoes inferred from an analytical formula for crack resonance frequencies 査読有り国際共著

Kimiko Taguchi,Hiroyuki Kumagai,Yuta Maeda,Roberto Torres

Journal of Geophysical Research: Solid Earth 123 巻頁： 7550 - 7565 2018年8月

Seismic velocity structure in the source region of the 2016 Kumamoto earthquake sequence, Japan 査読有り

Azusa Shito, Satoshi Matsumoto, Hiroshi Shimizu, Takahiro Ohkura, Hiroaki Takahashi, Shinichi Sakai, Tomomi Okada, Hiroki Miyamachi, Masahiro Kosuga, Yuta Maeda, Masayuki Yoshimi, Youichi Asano, Makoto Okubo

Geophysical Research Letters 44 巻頁： 7766 - 7772 2017年8月

Depth-dependent rupture mode along the Ecuador-Colombia subduction zone 査読有り国際共著

Masahiro Yoshimoto, Hiroyuki Kumagai, Wilson Acero, Gabriela Ponce, Freddy Vásconez, Santiago Arrais, Mario Ruiz, Alexandra Alvarado, Patricia Pedraza García, Viviana Dionicio, Orlando Chamorro, Yuta Maeda, Masaru Nakano

Geophysical Research Letters 44 巻 ( 5 ) 頁： 2203 - 2210 2017年3月

Modeling the dynamics of a phreatic eruption based on a tilt observation: Barrier breakage leading to the 2014 eruption of Mount Ontake, Japan 査読有り

Yuta Maeda, Aitaro Kato, Yoshiko Yamanaka

Journal of Geophysical Research: Solid Earth 122 巻 ( 2 ) 頁： 1007 - 1024 2017年3月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Although phreatic eruptions are common volcanic phenomena that sometimes result in significant disasters, their dynamics are poorly understood. In this study, we address the dynamics of the phreatic eruption of Mount Ontake, Japan, in 2014 based on analyses of a tilt change observed immediately (450 s) before the eruption onset. We conducted two sets of analysis: a waveform inversion and a modified phase-space analysis. Our waveform inversion of the tilt signal points to a vertical tensile crack at a depth of 1100 m. Our modified phase-space analysis suggests that the tilt change was at first a linear function in time that then switched to exponential growth. We constructed simple analytical models to explain these temporal functions. The linear function was explained by the boiling of underground water controlled by a constant heat supply from a greater depth. The exponential function was explained by the decompression-induced boiling of water and the upward Darcy flow of the water vapor through a permeable region of small cracks that were newly created in response to ongoing boiling. We interpret that this region was intact prior to the start of the tilt change, and thus, it has acted as a permeability barrier for the upward migration of fluids; it was a breakage of this barrier that led to the eruption.

DOI： 10.1002/2016JB013739

その他リンク： https://nagoya.repo.nii.ac.jp/records/24369

A generalized equation for the resonance frequencies of a fluid-filled crack 査読有り

Yuta Maeda, Hiroyuki Kumagai

Geophysical Journal International 209 巻 ( 1 ) 頁： 192 - 201 2017年1月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

Although a model of the resonance of a rectangular fluid-filled crack (crack model) is one of the most frequently used source models of long-period seismic events at volcanoes, there has been no analytical solution for the resonance frequencies. We previously proposed an empirical expression for the resonance frequencies as a mathematical function of the crack length, aperture, and properties of the fluid and the surrounding elastic medium. However, the expression contained an empirical constant that had to be investigated numerically for each crack aspect ratio and oscillation mode, a requirement that prevented widespread use of the expression. In the present study, we examined the theoretical basis for the expression. We assumed that the ratio of the crack wall displacement to the fluid pressure near each crack edge varied as the square root of the distance from the edge. Using this assumption, we showed theoretically that the previously proposed empirical analytical expression was a good approximation (difference <=2 per cent) to another more complete expression. This theoretical expression is a closed form of a mathematical function of the crack model parameters and oscillation mode number; there are no empirical constants to be determined numerically. The expression thus enabled us to analytically compute the resonance frequencies for arbitrary rectangular cracks, and the results were in good agreement (difference <=5 per cent) with numerical solutions. Resonance frequencies of cracks can be very easily predicted using this expression. This predictive ability may enhance our quantitative understanding of the processes that generate long-period events at volcanoes.

DOI： 10.1093/gji/ggx019

その他リンク： https://nagoya.repo.nii.ac.jp/records/24370

火山性地震の波形解析に基づく流体移動と噴火過程の研究招待有り査読有り

前田裕太

火山 61 巻 ( 2 ) 頁： 459-464 2016年6月

Monitoring eruption activity using temporal stress changes at Mount Ontake volcano 査読有り

Toshiko Terakawa, Aitaro Kato, Yoshiko Yamanaka, Yuta Maeda, Shinichiro Horikawa, Kenjiro Matsuhiro, Takashi Okuda

Nature Communications 7 巻頁： 10797 2016年2月

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