Infrasound Array Analysis of Debris Flow Activity and Implication for Early Warning
Infrasound Array Analysis of Debris Flow Activity and Implication for Early Warning
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DOI：
10.1029/2018jf004785
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发表时间：
2019-02-01
影响因子：
3.9
通讯作者：
Price, C.
中科院分区：
文献类型：
--
作者：
Marchetti, E.;Walter, F.;Price, C.
泥石流是一种严重的自然灾害，已开展研究，调查其触发机制，并确定和评价预警系统。我们提出了一个地震声学分析的泥石流活动在伊尔格拉本，瑞士，次声数据收集的小孔径阵列。事件被记录为持续时间长的紧急信号，地震和次声振幅与流量流量成比例。频谱内容是稳定的，地震波在8Hz处达到峰值，次声波在5Hz处达到峰值，这表明两个独立的弹性能量辐射过程，最有可能的是地震波的推移质输运和次声波的自由表面处的波。虽然次声信号的幅度和频率含量都在处理范围内，但大部分信号在阵列元件之间没有显示出任何相关性。我们认为，这是一个后果的贡献多个源的次声作用与可变的振幅和相位沿着表面的泥石流。在Illgraben，相干次声只记录从固定的来源，对应于检查坝内的通道。在这里，次声辐射增加，水坝成为主要的能源来源。这使得可以从远程和安全的位置使用次声阵列明确地识别伊尔格拉本泥石流的发生，其时间与基于通道内传感器的预警系统相似。泥石流是高山环境中的一种严重自然灾害，目前正在进行研究，以调查触发机制，并确定和评估预警系统。我们提出了一个地震声学分析的泥石流活动在Illgraben，瑞士，次声数据收集的第一次与次声传感器阵列部署在一个安全的位置外的通道。这个地震声学实验提供了有趣的限制能量在地面和大气中的相互辐射的流动。此外，次声天线的使用允许第一次仔细分析次声辐射的机制，我们将其建模为具有可变相位的扩展能量源。此外，该阵列能够探测到泥石流穿过水坝或地形台阶时的情况，即使这发生在很远的距离（> 2公里），尽管从记录地点看不到。对于Illgraben的具体情况，这使得可以明确地识别泥石流的发生，其时间与基于通道内传感器的预警系统相似。这清楚地表明，次声阵列可用作泥石流活动的新预警系统。
Debris flows constitute a severe natural hazard and studies are performed to investigate triggering mechanisms and to identify and evaluate early warning systems. We present a seismoacoustic analysis of debris flow activity at Illgraben, Switzerland, with infrasound data collected with a small aperture array. Events are recorded as emergent signals of long duration, with seismic and infrasound amplitudes scaling with the flow discharge. The spectral content is stable and peaking at 8Hz for the seismic and at 5Hz for the infrasound that suggests two separate processes of elastic energy radiation, most likely bed-load transport for the seismic and waves at the free surface for the infrasound. Although amplitude and frequency content of the infrasound signal are well within the processing limits, most of the signal is not showing any correlation among the array elements. We suggest that this is a consequence of the contribution of multiple sources of infrasound acting with variable amplitude and phase along the surface of the debris flow. At Illgraben, coherent infrasound is recorded only from fixed sources, corresponding to check dams within the channel. Here infrasound radiation is increased and the dams turn into predominant sources of energy. This allows to unambiguously identify the occurrence of debris flow at Illgraben with the infrasound array, from a remote and safe position and with a timing that is similar to the early warning system based on in-channel sensors. This clearly shows how infrasound arrays could be used as an efficient early warning systems.Plain Language Summary Debris flows constitute a severe natural hazard in alpine environments, and studies are currently performed to investigate triggering mechanisms and to identify and evaluate early warning systems. We present a seismoacoustic analysis of debris flow activity at Illgraben, Switzerland, with infrasound data collected for the first time with an array of infrasound sensors deployed outside the channel in a safe position. This seimoacoustic experiment is providing interesting constraints on the mutual radiation of energy in the ground and in the atmosphere by the flow. Moreover, the use of the infrasound antenna allowed for the first time to carefully analyze the mechanism of infrasound radiation that we model as an extended source of energy with variable phase. Moreover, the array is able to detect the debris flow when it crosses dams or topography steps, even if this occurs at large distance (>2km) and despite not being visible from the recording site. For the specific case of Illgraben, this allows to unambiguously identifying the occurrence of debris flow with a timing that is similar to the early warning system based on in-channel sensors. This clearly shows how infrasound arrays could be used as new early warning systems for debris flow activity.