Scholarlink

<p>Eruption models developed using the waveform inversion method for explosion earthquakes differ across studies, and a unified model has not been established. Here, Vulcanian eruption processes of the Sakurajima volcano, Japan, were clarified using seismic waveform inversion analysis in the long- and very-long period bands for two specific events: one with a clear preceding infrasound phase (July 17, 2022) and the other with almost no preceding infrasound phase (July 24, 2022). The waveform inversion analysis used the layered velocity structure obtained from artificial seismic experiments and the detailed topography of the Sakurajima edifice. In both events, the single-force component, in addition to the moment tensor, was a necessary parameter for explaining the eruption process. The source location of the explosion earthquake on July 17 was 480&#xa0;m below sea level (1140&#xa0;m below the crater), while that of the explosion earthquake on July 24 was 440&#xa0;m above sea level (220&#xa0;m below the crater). In the former event, the magma reached supersaturation at depth by the time of the explosion. Magma ascent and bubble growth appeared as the expansion and contraction of the crack in the volcanic conduit beneath the crater. In addition, as the magma rose, vertical drag and reaction forces were exerted on the conduit. In the latter event, magma supersaturation remained shallow within the conduit. Following rapid magma ejection from the shallow part of the conduit and the expulsion of volcanic bombs, the vesiculation level of magma in the conduit decreased, resulting in gradual ash ejection. The preceding phase of infrasound was seen in the July 17 event but not in the July 24 event; the presence or absence of the preceding phase did not seem to determine the strength of the lava plug since there were six events between the two events, and the rate of SO<sub>2</sub> emission during that period showed an increasing trend. Overall, these findings highlight the necessity of considering the single-force component and the moment tensor to explain the eruption process. This study also provides insights into the source locations of explosion earthquakes, as well as the dynamics of magma ascent and bubble growth.</p> Graphical Abstract <p></p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Source process of Vulcanian explosion earthquakes at Sakurajima volcano, Japan, derived from seismic waveform inversion analysis in the very-long and long period bands and infrasound signals

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2025年9月30日

查看全文
  • Ryohei Takahashi,
  • Haruhisa Nakamichi

摘要

Eruption models developed using the waveform inversion method for explosion earthquakes differ across studies, and a unified model has not been established. Here, Vulcanian eruption processes of the Sakurajima volcano, Japan, were clarified using seismic waveform inversion analysis in the long- and very-long period bands for two specific events: one with a clear preceding infrasound phase (July 17, 2022) and the other with almost no preceding infrasound phase (July 24, 2022). The waveform inversion analysis used the layered velocity structure obtained from artificial seismic experiments and the detailed topography of the Sakurajima edifice. In both events, the single-force component, in addition to the moment tensor, was a necessary parameter for explaining the eruption process. The source location of the explosion earthquake on July 17 was 480 m below sea level (1140 m below the crater), while that of the explosion earthquake on July 24 was 440 m above sea level (220 m below the crater). In the former event, the magma reached supersaturation at depth by the time of the explosion. Magma ascent and bubble growth appeared as the expansion and contraction of the crack in the volcanic conduit beneath the crater. In addition, as the magma rose, vertical drag and reaction forces were exerted on the conduit. In the latter event, magma supersaturation remained shallow within the conduit. Following rapid magma ejection from the shallow part of the conduit and the expulsion of volcanic bombs, the vesiculation level of magma in the conduit decreased, resulting in gradual ash ejection. The preceding phase of infrasound was seen in the July 17 event but not in the July 24 event; the presence or absence of the preceding phase did not seem to determine the strength of the lava plug since there were six events between the two events, and the rate of SO2 emission during that period showed an increasing trend. Overall, these findings highlight the necessity of considering the single-force component and the moment tensor to explain the eruption process. This study also provides insights into the source locations of explosion earthquakes, as well as the dynamics of magma ascent and bubble growth.

Graphical Abstract