Very-long-period pulses at Asama volcano, central Japan, inferred from dense seismic observations
Very-long-period pulses at Asama volcano, central Japan, inferred from dense seismic observations
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DOI：
10.1111/j.1365-246x.2011.04938.x
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发表时间：
2011-04-01
影响因子：
2.8
通讯作者：
Takeo, Minoru
中科院分区：
文献类型：
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作者：
Maeda, Yuta;Takeo, Minoru
我们观察到地震事件组成的几个单侧速度脉冲的持续时间为5-30秒（以下称为甚长周期或VLP脉冲），使用14个宽带地震仪安装在日本浅间火山山顶附近的地区。粒子运动不指向一个单一的源位置，尽管他们的直线性，这表明一个非各向同性的源机制，以及路径效应。我们进行了矩张量反演分析，这些事件使用的绿色的功能，不仅平移运动，而且倾斜运动。最合适的震源位置位于火山口中心以北，火山口底部以下100-150米深处。弯矩-张量解的主值比可近似为5：3：2，这表明裂纹和圆柱体的组合，裂纹的走向和倾角均接近70 °，圆柱体的对称轴相对于垂直方向倾斜近30 °。力矩张量的时间历程表明，在源区域的初始突然增压和随后的逐渐降压。我们试图模拟VLP脉冲在浅间火山考虑流入和流出的气体在源腔，在另一个更深的水库沸腾补偿。
We observed seismic events consisting of several one-sided velocity pulses with durations of 5-30 s (hereafter called very-long-period or VLP pulses) using up to 14 broad-band seismometers installed near the summit area of Asama volcano, Japan. Particle motions do not point to a single source location despite their rectilinearities, suggesting a non-isotropic source mechanism, together with path effect. We conducted moment-tensor inversion analyses for these events using the Green's functions of not only translational motions but also of tilt motions. The best-fitting source locations are located north of the crater centre, at depths of 100-150 m below the crater bottom. The principal value ratios of moment-tensor solutions can be approximated as 5: 3: 2, which is indicative of a combination of a tensile crack and a cylinder, with the strike and dip angle of the crack both being nearly 70 degrees, and symmetry axis of the cylinder being inclined by nearly 30 degrees from the vertical. The time histories of moment-tensors are indicative of an initial sudden pressurization and subsequent gradual depressurization at the source region. We sought to model VLP pulses at Asama volcano by considering the inflow and outflow of gas at the source cavity, compensated by boiling in another deeper reservoir.