Journal of Geophysical Research: Solid Earth On corner frequencies, attenuation, and low-frequency earthquakes Slow Slip Phenomena and Plate Boundary Processes
Journal of Geophysical Research: Solid Earth On corner frequencies, attenuation, and low-frequency earthquakes Slow Slip Phenomena and Plate Boundary Processes
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地球物理研究杂志：固体地球关于角频率、衰减和低频地震慢滑现象和板块边界过程
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通讯作者：
A. Evangelou
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作者：
G. Papathanasiou;M. Papandreou;A. Galanos;E. Kortianou;E. Tsepis;V. Kalfakakou;A. Evangelou
我们最近提出，低频地震（lfe）几乎恒定的持续时间（以及构造震动的频带限制）表现出与常规地震根本不同的瞬间持续时间尺度，并且最容易解释为在大致恒定尺寸的岩石上破裂。在这项工作中，我们通过衰减采用定性论证来反对潜在偏差。在这里，我们通过一种分析来更定量地研究衰减的作用，这种分析避免了特定源（例如，Brune）模型的规范，并依赖于粒子速度谱最大值作为表观角频率的定义。通过分析，将饱和频率正式定义为视角频率趋于无穷大时的极限值。饱和频率，一个等价于fmax的形式，可以用来设置路径平均质量因子Q的边界。我们将这些关系应用于温哥华岛下的深部地壳和岩内地震，以估计大块地壳衰减参数，这些参数随后用于校正我们早期工作中报道的lfe的表观角频率测量。由于大块地壳结构引起的衰减偏差很小，对该研究的主要结论的影响可以忽略不计。然而，对海洋玄武岩衰减的实验室和地震折射测量的回顾以及高P - S LFE角频率比的证据表明，伴随高孔隙流体压力的强烈、高度局部化、近源衰减可能会通过高频耗尽导致LFE的带限性质。
We have recently suggested that the nearly constant duration of low-frequency earthquakes (LFEs) (and, equivalently, the band limitation of tectonic tremor) manifests a moment-duration scaling that is fundamentally different from regular earthquakes and is most easily explained as rupture on asperities of roughly constant dimension. In that work, we employed qualitative arguments against potential bias by attenuation. Here we examine the role of attenuation more quantitatively through an analysis that avoids specification of particular source (e.g., Brune) models and relies on the particle velocity spectral maximum as the definition of apparent corner frequency. The analysis leads to the formal definition of a saturation frequency as the limiting value of apparent corner frequency as the true corner frequency tends infinity. The saturation frequency, a formal equivalent to f max , can be used to set bounds on path-averaged quality factor Q . We apply these relations to deep crustal and intraslab earthquakes beneath Vancouver Island to estimate bulk crustal attenuation parameters that are subsequently used to correct apparent corner frequency measurements of LFEs reported in our earlier work. The attenuation bias due to bulk crustal structure is shown to be small, with negligible effect on the principal conclusions of that study. However, a review of laboratory and seismic refraction measurements of attenuation in oceanic basalts and evidence for high P -to- S LFE corner frequency ratios raises the possibility that strong, highly localized, near-source attenuation accompanying high pore-fluid pressures could cause the bandlimited nature of LFEs through the depletion of high frequencies.