S-wave modelling of the Showa-Shinzan lava dome in Usu Volcano, Northern Japan, from seismic observations
S-wave modelling of the Showa-Shinzan lava dome in Usu Volcano, Northern Japan, from seismic observations
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DOI：
10.1093/gji/ggac111
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发表时间：
2022-05-19
影响因子：
2.8
通讯作者：
Aoki，Yosuke
中科院分区：
文献类型：
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作者：
Takeo，Akiko;Nishida，Kiwamu;Aoki，Yosuke
为了获得内部 S 波速度结构，我们在昭和新山熔岩穹顶及其周围使用 21 个 1 Hz 地震仪进行了被动地震活动，该熔岩穹顶在 1943 年至 1945 年日本有珠火山喷发期间出现。在活动之前，我们校准了地震仪，发现地震仪之间存在小于 1-2° 的轻微相位响应差异。活动结束后，我们通过地震站点之间垂直分量环境噪声记录的互相关来提取地震波场。我们开发了一种假设层状结构自动测量瑞利波相速度的新方法，最终获得了顶区、顶区和底区的1-DS波速模型。所获得的侵入熔岩穹丘正下方的横波速度比周围地区高出百分之几十，直到海平面以下数百米，这表明熔岩穹丘根部存在狭窄但深的存在。在顶峰区域熔岩穹顶内部浅于～50 m的深度处获得的S波速度为～1 km s−1，显着低于根据先前μ介子射线照相研究和常规标度估计的2.3 × 103kg m−3密度所预测的速度，表明熔岩穹顶破裂的影响。
To obtain an internalS-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°. 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 1-DS-wave velocity models in summit, roof and base regions. The obtainedS-wave velocity right beneath the intruded lava dome is higher than that in surrounding areas by a few tens of per cent down to a few hundred metres below sea level, indicating narrow but deep existence of the root of the lava dome. The obtainedS-wave velocity at depths shallower than ∼50 m inside the lava dome in the summit area was ∼1 km s−1, significantly lower than that predicted from the density of 2.3 × 103kg m−3estimated in previous muon-radiography studies and a conventional scaling, indicating the effect of cracking in the lava dome.