Imaging preeruptive and coeruptive structural and mechanical changes of a volcano with ambient seismic noise
Imaging preeruptive and coeruptive structural and mechanical changes of a volcano with ambient seismic noise
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DOI：
10.1002/2013jb010399
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发表时间：
2013-12
期刊：
影响因子：
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通讯作者：
A. Obermann;T. Planès;É. Larose;Michel Campillo
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文献类型：
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作者：
A. Obermann;T. Planès;É. Larose;Michel Campillo
预测火山爆发的位置对于火山地区的风险管理至关重要。定位与潜在喷发相关的地下结构变化也是更好地了解火山动态的一个关键问题。利用波动物理学的最新成果，我们开发了一种成像程序，该程序基于多重散射波对非均匀介质中微弱变化的敏感性。该过程允许定位所研究介质的机械和散射特性的变化。我们研究环境地震噪声从19个宽带站在活火山皮通德拉Fournaise留尼汪岛，记录从2010年6月至12月。在此期间，在两个不同的地点发生了两次火山爆发。我们计算的噪声互相关，并研究两种类型的变化尾波：视速度的变化有关的介质的弹性性质的变化;和，波形退相干与散射的变化，从而地质结构。我们观察到，这两个参数的时间变化提供了潜在的火山爆发的前兆在皮通德拉Fournaise。根据火山喷发前和喷发时两个参数的变化所确定的位置与实际喷发活动情况吻合较好。这些数据表明，环境噪声相关性的尾波包含确定性的信息在一个活火山的喷发过程的位置。我们的分析提供了一个原始的和显着的限制，即将举行的火山爆发的本地化。
Forecasting the location of an eruption is of primary importance for risk management in volcanic regions. Locating the underground structural changes associated with a potential eruption is also a key issue to better understand the dynamics at work in a volcano. Using recent results in wave physics, we develop an imaging procedure that is based on the sensitivity of multiply scattered waves to weak changes in heterogeneous media. This procedure allows to locate changes in both mechanical and scattering properties of the studied medium. We study ambient seismic noise from 19 broadband stations at the active volcano Piton de la Fournaise on Reunion Island, recorded from June to December 2010. During this period, two volcanic eruptions occurred at two different locations. We calculate the noise cross correlations and study two types of changes in the coda: apparent velocity variations related to changes in the elastic properties of the medium; and, waveform decoherence associated with variations in the scattering, and thus the geological structures. We observe that the temporal variations of both of these parameters provide potential precursors of volcanic eruptions at Piton de la Fournaise. The locations determined from the preeruptive and coeruptive changes in both parameters are in good agreement with the actual eruptive activities. These data demonstrate that the coda of ambient noise correlations contains deterministic information on the locations of the eruptive processes in an active volcano. Our analysis offers an original and significant constraint for the localization of forthcoming volcanic eruptions.