Infrasonic tremor wavefield of the Pu`u `Ō`ō crater complex and lava tube system, Hawaii, in April 2007
Infrasonic tremor wavefield of the Pu`u `Ō`ō crater complex and lava tube system, Hawaii, in April 2007
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2007 年 4 月夏威夷 Pu`u `Ō`ō 火山口复合体和熔岩管系统的次声震波场
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发表时间：
2010
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通讯作者：
M. Garcés
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作者：
R. Matoza;D. Fee;M. Garcés
[1]在夏威夷夏威夷基拉韦厄火山的普乌奥火山口复合体，长期喷发的火山活动产生了持续的次声震颤，这种震颤几乎连续记录了数月至数年。先前的研究表明，这种次声震颤波场可以在>10 km的范围内记录。然而，这种震颤相对于环境噪声水平的低信号功率导致在该范围内对信号可检测性的显著传播效应。在2007年4月，我们补充了一个宽带次声阵列在12.5公里的Pu`u ``ō（MENE）与一个类似的阵列在12.4公里的源（KIPU）。额外的近距离数据能够进一步评估对流层传播效应，并为研究火山源过程提供更高的信噪比。次声震颤源似乎由至少两个独立的物理过程组成。我们认为，气泡云振荡在火山口复杂的岩浆管道下翻滚可能会产生一个宽带分量的震颤。由于岩浆-空气界面的异常透明性，起源于浅岩浆管道中的低频声可以有效地将次声辐射到大气中。我们进一步提出，更尖锐的尖峰音调与复杂的时间演变可能会导致振荡的相互作用的低速气体射流与固体喷口边界的过程类似的孔音或哨声喷嘴。次声震颤到达KIPU时的中位方位角为0.67 °。来自火山口复合体南部（中位方位角为77°）延伸的熔岩管系统的额外次声信号和可听声音与新熔岩管天窗处的湍流脱气活动相吻合。我们的观察表明，声学研究可能有助于理解持久的连续脱气和不稳定的流动动力学在基拉韦厄火山。
[1] Long-lived effusive volcanism at the Pu`u `Ō`ō crater complex, Kilauea Volcano, Hawaii produces persistent infrasonic tremor that has been recorded almost continuously for months to years. Previous studies showed that this infrasonic tremor wavefield can be recorded at a range of >10 km. However, the low signal power of this tremor relative to ambient noise levels results in significant propagation effects on signal detectability at this range. In April 2007, we supplemented a broadband infrasound array at ∼12.5 km from Pu`u `Ō`ō (MENE) with a similar array at ∼2.4 km from the source (KIPU). The additional closer-range data enable further evaluation of tropospheric propagation effects and provide higher signal-to-noise ratios for studying volcanic source processes. The infrasonic tremor source appears to consist of at least two separate physical processes. We suggest that bubble cloud oscillation in a roiling magma conduit beneath the crater complex may produce a broadband component of the tremor. Low-frequency sound sourced in a shallow magma conduit may radiate infrasound efficiently into the atmosphere due to the anomalous transparency of the magma-air interface. We further propose that more sharply peaked tones with complex temporal evolution may result from oscillatory interactions of a low-velocity gas jet with solid vent boundaries in a process analogous to the hole tone or whistler nozzle. The infrasonic tremor arrives with a median azimuth of ∼67° at KIPU. Additional infrasonic signals and audible sounds originating from the extended lava tube system to the south of the crater complex (median azimuth ∼77°) coincided with turbulent degassing activity at a new lava tube skylight. Our observations indicate that acoustic studies may aid in understanding persistent continuous degassing and unsteady flow dynamics at Kilauea Volcano.