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Solidified magma reservoir derived from active source seismic experiments in the Aira caldera, southern Kyushu, Japan
Earth, Planets and Space ( IF 3.0 ) Pub Date : 2023-10-18 , DOI: 10.1186/s40623-023-01919-z
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

The Aira caldera, located in southern Kyushu, Japan, originally formed 100 ka, and its current shape reflects the more recent 30 ka caldera-forming eruptions (hereafter, called the AT eruptions). This study aimed to delineate the detailed two-dimensional (2D) seismic velocity structure of the Aira caldera down to approximately 15 km, by means of the travel-time tomography analysis of the seismic profile across the caldera acquired in 2017 and 2018. A substantial structural difference in thickness in the subsurface low-velocity areas in the Aira caldera between the eastern and western sides, suggest that the Aira caldera comprises at least two calderas, identified as the AT and Wakamiko calderas. The most interesting feature of the caldera structure is the existence of a substantial high-velocity zone (HVZ) with a velocity of more than 6.8 km/s at depths of about 6–11 km beneath the central area of the AT caldera. Because no high ratio of P- to S-wave velocity zones in the depth range were detected from the previous three-dimensional velocity model beneath the AT caldera region, we infer that the HVZ is not an active magma reservoir but comprises a solidified and cool remnant. In addition, a poorly resolved low-velocity zone around 15 km in depth suggests the existence of a deep active magma reservoir. By superimposing the distribution of the known pressure sources derived from the observed ground inflation and the volcanic earthquake distribution onto the 2D velocity model, the magma transportation path in the crust was imaged. This image suggested that the HVZ plays an important role in magma transportation in the upper crust. Moreover, we estimated that the AT magma reservoir in the 30 ka Aira caldera-forming eruptions has the total volume of 490 km3 DRE and is distributed in a depth range of 4–11 km.

Graphical Abstract



中文翻译:

日本九州南部姫良火山口主动震源地震实验得出的凝固岩浆储层

位于日本九州南部的姫良火山口最初形成于100 ka,其目前的形状反映了最近30 ka火山口形成的喷发(以下称为AT喷发)。本研究旨在通过对 2017 年和 2018 年获取的整个破火山口地震剖面的走时层析成像分析,描绘出约 15 公里范围内的艾拉破火山口的详细二维 (2D) 地震速度结构。姶良破火山口东西两侧地下低速区的厚度结构差异表明,姶良破火山口至少包含两个破火山口,分别是AT破火山口和若美子破火山口。破火山口结构最有趣的特征是在 AT 破火山口中心区域下方约 6-11 公里的深度存在一个速度超过 6.8 公里/秒的大量高速区 (HVZ)。由于之前的三维速度模型在AT破火山口区域下方没有检测到该深度范围内纵横波速度比例较高的区域,因此我们推断HVZ不是一个活跃的岩浆库,而是由一个凝固的冷岩浆库组成。剩。此外,深度约15公里处分辨率较差的低速带表明存在深层活动岩浆库。通过将观测到的地面膨胀和火山地震分布得出的已知压力源的分布叠加到二维速度模型上,对地壳中的岩浆输送路径进行了成像。该图像表明 HVZ 在上地壳岩浆输送中发挥着重要作用。此外,我们估计30 ka Aira破火山口喷发中的AT岩浆库总体积为490 km 3 DRE,分布深度为4~11 km。

图形概要

更新日期:2023-10-19
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