Seismic scattering and attenuation at volcanoes, thought to be strongest on the Earth, can be used to map volcanic feeding systems. We systematically analyzed high‐frequency (5–10 Hz) seismograms of volcano‐tectonic earthquakes at Galeras volcano (Colombia) and active sources at Kirishima, Unzen, Bandai, and Iwate volcanoes (Japan) to investigate their scattering and attenuation characteristics. The envelope widths estimated from these seismograms were compared with those calculated by Monte Carlo envelope simulations for 1D layered models parameterized by the scattering mean free path and the quality factor of medium attenuation for S waves. Our results indicated a surficial, highly heterogeneous, and attenuative layer up to around 1 km thickness at all studied volcanoes. The strongest heterogeneities at volcanoes thus exist in a thin surface layer, likely comprising unconsolidated and/or highly fractured materials. Using the space‐weighting function for diffusive wavefields, we mapped the residuals between observed envelope widths and those calculated with our estimated 1D models at Kirishima, Unzen, Bandai, and Iwate. These maps showed spatial distributions of the envelope‐width residuals were unique to each volcano and correlated with P wave velocity tomographic images. Areas of positive residuals correspond to low‐velocity anomalies and thus to heterogeneous, strongly scattering rocks, whereas areas of negative residuals correspond to high‐velocity anomalies and thus less heterogeneous volcanic or basement rocks. Our results demonstrate that envelope widths can improve the characterization of scattering and attenuation structures beneath volcanoes.

中文翻译：

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从天然和主动地震震源的包络线宽度推断火山的散射和衰减特性

火山中的地震散射和衰减（据认为是地球上最强的）可以用来绘制火山的馈电系统图。我们系统地分析了Galeras火山（哥伦比亚）和Kirishima，Unzen，Bandai和Iwate火山（日本）的火山构造地震的高频（5-10 Hz）地震图，以研究其散射和衰减特征。从这些地震图估计的包络宽度与通过蒙特卡洛包络模拟计算的一维分层模型所计算的包络宽度相比较，该参数由散射平均自由程和S介质衰减的品质因数参数化波浪。我们的研究结果表明，在所有研究过的火山中，表层的高度非均质性和衰减性层厚约1 km。因此，火山中最强的非均质性存在于薄的表层中，可能包含未固结和/或高度破裂的物质。使用弥散波场的空间加权函数，我们将观测到的包络线宽度与我们在雾岛，云仙，万代和岩手县的估计一维模型计算出的残差之间作图。这些图显示了每个火山唯一的包膜宽度残差的空间分布，并且与P相关。波速断层图像。正残差区域对应于低速异常，因此对应于非均质强散射岩石，而负残差区域对应于高速异常，因此对应于非均质火山岩或基底岩。我们的结果表明，包络线宽度可以改善火山下方散射和衰减结构的特征。