Investigating Spectral Estimates of Stress Drop for Small to Moderate Earthquakes With Heterogeneous Slip Distribution: Examples From the 2016–2017 Amatrice Earthquake Sequence
Investigating Spectral Estimates of Stress Drop for Small to Moderate Earthquakes With Heterogeneous Slip Distribution: Examples From the 2016–2017 Amatrice Earthquake Sequence
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DOI：
10.1029/2022jb025022
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发表时间：
2023-05
期刊：
影响因子：
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通讯作者：
G. Calderoni;R. Abercrombie
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文献类型：
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作者：
G. Calderoni;R. Abercrombie
谱应力降的估计是理解控制地震破裂和高频地面运动的因素的基础，但已知包括大的、约束不佳的不确定性。我们利用2016-2017年意大利亚平宁地区的地震序列（最大的地震发生在诺尔恰，Mw 6.3）来调查这些不确定性及其原因。在阿马特里切（Mw 6.0）和维索（Mw 5.9）附近类似大小的事件可以更好地进行约束相对分析。我们计算了30个较大事件的S波源谱、角频率和谱应力降。我们比较了经验方法和模型方法来分离源光谱和计算源参数；我们还将我们的结果与已发表的研究结果进行了比较。随机和系统的研究间差异都大于任何单个研究报告的标准误差。在不同的研究中，报告的压力下降的依赖程度各不相同，广义反演的依赖程度最大，而基于个体事件的方法的依赖程度最小。事件间应力降的相对谱估计更为一致；所有方法估计的阿马特里切地震的应力降都高于同等规模的维索地震。相比之下，这两次地震的有限断层反演发现，Visso地震具有较大的高滑动集中区域，而Amatrice地震具有多个低滑动子事件。阿马特里切地震的频谱比维索地震的频谱包含更多的高频能量。这一比较表明，高频谱应力降的一致测量表明更高的高频地震动，但可能对应更大的破裂复杂性，而不是更高的应力降。
Estimates of spectral stress drop are fundamental to understanding the factors controlling earthquake rupture and high frequency ground motion, but are known to include large, poorly‐constrained uncertainties. We use earthquakes from the 2016–2017 sequence in the Italian Appenines (largest event at Norcia, Mw 6.3) to investigate these uncertainties and their causes. The similarly‐sized events near Amatrice (Mw 6.0) and Visso (Mw 5.9) enable better constrained relative analysis. We calculate S wave source spectra, corner frequencies, and spectral stress drop for 30 of the larger events. We compare both empirical and modeling approaches to isolate the source spectra and calculate source parameters; we also compare our results with those from published studies. Both random and systematic inter‐study variations are larger than the standard errors reported by any individual study. The reported magnitude dependence of stress drop varies between studies, being largest for generalized inversions and smallest for more individual event based approaches. The relative spectral estimates of inter‐event stress drop are more consistent; all approaches estimated higher stress drop in the Amatrice earthquake than the similar‐sized Visso earthquake. In contrast, finite fault inversions of these two earthquakes found that the Visso earthquake had the larger region of concentrated, higher slip, whereas the Amatrice earthquake had multiple, lower slip, subevents. The Amatrice spectra contain more high frequency energy than those of the Visso earthquake. This comparison suggests that consistent measurement of a higher spectral stress drop indicates greater high‐frequency ground motion but may correspond to greater rupture complexity rather than higher stress drop.