Improved Estimation of Glacial-Earthquake Size Through New Modeling of the Seismic Source
Improved Estimation of Glacial-Earthquake Size Through New Modeling of the Seismic Source
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通过地震源的新模型改进冰川地震规模的估计
DOI：
10.1029/2021jf006384
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Olsen K
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作者：
Olsen K
格陵兰冰川每年发生的亿吨级冰山崩解事件的数量正在增加，这是格陵兰冰盖加速质量损失的更大趋势的一部分。虽然大型冰解事件的视觉观察是罕见的，但这些冰解事件所产生的160次冰川地震目前每年都被区域和全球地震台站记录下来。冰山大小和MCSF之间的经验关系，是冰川地震大小的一种概括性衡量标准，最近由Olsen和Nettles（2019）证明，https://doi.org/10.1029/2019JF005054。然而，MCSF是已知的是在模拟地震源的选择敏感。我们结合了对地震源的限制，从实验室研究的产犊和测试多个源的时间函数，使用合成和观察到的冰川地震波形。我们发现，一个简单的，固定的时间函数的形状通知实验室结果大大提高了地震规模的估计。使用我们首选的源模型的实验中，估计力值与真实力值的平均比值为1.03，而以前研究中使用的模型的平均比值为0.3。我们发现，从波形建模中估计的最大力值对模型选择的依赖程度远远低于MCSF，因此更倾向于将最大力作为冰川地震规模的度量。使用合成和真实的数据，我们确认了最大力和冰山质量之间的相关性。我们的结果支持在地震观测值和控制冰川崩解的物理参数之间建立有用的缩放关系的可能性。
The number of gigaton‐sized iceberg‐calving events occurring annually at Greenland glaciers is increasing, part of a larger trend of accelerating mass loss from the Greenland Ice Sheet. Though visual observation of large calving events is rare, ∼60 glacial earthquakes generated by these calving events are currently recorded each year by regional and global seismic stations. An empirical relationship between iceberg size andMCSF, a summary measure of glacial‐earthquake size, was recently demonstrated by Olsen and Nettles (2019), https://doi.org/10.1029/2019JF005054. However,MCSFis known to be sensitive to choices made in modeling the seismic source. We incorporate constraints on the seismic source from laboratory studies of calving and test multiple source time functions using synthetic and observed glacial‐earthquake waveforms. We find that a simple, fixed time function with a shape informed by laboratory results greatly improves estimates of earthquake size. The average ratio of estimated to true peak force values is 1.03 for experiments using our preferred source model, compared with an average of 0.3 for models used in previous studies. We find that maximum‐force values estimated from waveform modeling depend far less on model choices than doesMCSF, and therefore prefer maximum force as a measure of glacial‐earthquake size. Using both synthetic and real data, we confirm a correlation between maximum force and iceberg mass. Our results support the possibility of developing useful scaling relationships between seismic observables and physical parameters controlling glacier calving.