Resolving Differences in the Rupture Properties of M5 Earthquakes in California Using Bayesian Source Spectral Analysis
Resolving Differences in the Rupture Properties of M5 Earthquakes in California Using Bayesian Source Spectral Analysis
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DOI：
10.1029/2021jb023526
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发表时间：
2022-03
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影响因子：
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通讯作者：
D. Trugman
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作者：
D. Trugman
地震波形的频谱可以为破裂过程提供重要的见解，但对这些频谱的分析和解释很少是简单的。在这里，我们开发了一个贝叶斯框架，该框架包含光谱分析的固有数据和建模不确定性，以推断关键源属性。该方法使用谱比方法来校正观测到的附近地震的 S 波谱的路径和场地衰减。然后的目标是求解序列中每次地震的三个震源参数（地震矩、角频率和高频衰减率）的联合后验概率分布，以及具有良好方位站覆盖的选定目标事件的破裂方向性测量。虽然计算量很大，但该技术提供了对参数权衡和不确定性的定量理解，并允许通过先验分布对所有源参数施加物理约束，从而在数据有限时指导反演。我们通过详细分析南加州 14 个不同的 M5 级目标事件的源属性来演示该方法，这些事件跨越了广泛的构造体系和断层系统。这些突出的地震虽然规模相当，但其震源特性和方向性表现出明显的多样性，具有清晰的空间模式、深度依赖的趋势以及对单边方向性的偏好。这些连贯的空间变化源特性表明，构造环境、震源深度或断层带特征的区域差异可能会驱动破裂过程的变化，这对于我们理解地震物理及其与灾害的关系具有重要意义。
The spectra of earthquake waveforms can provide important insight into rupture processes, but the analysis and interpretation of these spectra is rarely straightforward. Here we develop a Bayesian framework that embraces the inherent data and modeling uncertainties of spectral analysis to infer key source properties. The method uses a spectral ratio approach to correct the observed S‐wave spectra of nearby earthquakes for path and site attenuation. The objective then is to solve for a joint posterior probability distribution of three source parameters—seismic moment, corner frequency, and high‐frequency falloff rate—for each earthquake in the sequence, as well as a measure of rupture directivity for select target events with good azimuthal station coverage. While computationally intensive, this technique provides a quantitative understanding of parameter tradeoffs and uncertainties and allows one to impose physical constraints through prior distributions on all source parameters, which guide the inversion when data is limited. We demonstrate the method by analyzing in detail the source properties of 14 different target events of magnitude M5 in southern California that span a wide range of tectonic regimes and fault systems. These prominent earthquakes, while comparable in size, exhibit marked diversity in their source properties and directivity, with clear spatial patterns, depth‐dependent trends, and a preference for unilateral directivity. These coherent spatial variations source properties suggest that regional differences in tectonic setting, hypocentral depth or fault zone characteristics may drive variability in rupture processes, with important implications for our understanding of earthquake physics and its relation to hazard.