Robust Estimation of Rupture Properties at Propagating Front of Laboratory Earthquakes
Robust Estimation of Rupture Properties at Propagating Front of Laboratory Earthquakes
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实验室地震传播前沿破裂特性的鲁棒估计
DOI：
10.1029/2018jb016797
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
and F. Yamashita
中科院分区：
文献类型：
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作者：
Xu;S.;E. Fukuyama;and F. Yamashita
地震破裂沿断层界面的传播取决于控制摩擦定律。尽管基于实验室测量提出了各种摩擦定律，但这些测量在多大程度上捕获了真实的断裂特性仍然存在不确定性。通过将实验室地震与数值模拟破裂进行比较，我们发现破裂前沿内部的某些特性可能并不总是能够在现实世界中直接测量，因为破裂前沿区域尺寸缩小（洛伦兹收缩）导致分辨率缺乏。相反，我们提出了一种间接方法，通过使用数值合成同时拟合破裂前沿的轨迹和详细的应变波形形状，来稳健地估计实验室地震的破裂特性。在当前数据分辨率下，基于弱滑摩擦模型，我们的方法除了对断裂能的常规约束之外，还可以提供对弱滑距离的上限约束。这种新方法对 26 次实验室地震的应用表明，破裂特性（方向性、传播速度、断裂能和摩擦强度）可能会随着地震周期而波动。事后检查进一步表明，我们的直接测量很大程度上反映了破裂前沿之外的变形特征。由于其他研究中可能存在关于破裂前沿内部直接测量的可行性的相同问题，因此我们的工作对先前推导的摩擦定律的准确性提出了质疑，解决了校准测量位置和分辨率的需要，并提供了一种检查估计破裂特性的自洽性的方法。
Earthquake rupture propagation along a fault interface depends on the governing friction law. Although a variety of friction laws have been proposed based on measurements made in the lab, uncertainty remains regarding to what extent those measurements capture the true rupture properties. By comparing laboratory earthquakes with numerically simulated ruptures, we find that certain properties inside the rupture front may not always be accessible to direct measurements in the real world, due to a lack of resolution caused by the shrinking size of rupture front zone (Lorentz contraction). Instead, we propose an indirect method to robustly estimate rupture properties of laboratory earthquakes, by simultaneously fitting both the trajectory of rupture front and the detailed strain waveform shape using numerical synthetics. Under the current data resolution and on the basis of a slip‐weakening friction model, our method can provide upper bound constraints on slip‐weakening distance, in addition to regular constraints on fracture energy. Application of this new method to 26 laboratory earthquakes shows that rupture properties (directivity, propagation speed, fracture energy, and frictional strength) can fluctuate over earthquake cycles. Post hoc examination further suggests that our direct measurements largely reflect the deformation features outside the rupture front. As the same issue on the feasibility of direct measurements inside the rupture front may exist in other studies, our work questions the accuracy of previously derived friction laws, addresses the need for calibrating measurement location and resolution, and provides a means for examining the self‐consistency of estimated rupture properties.