Effects of complicated 3‐D rupture geometries on earthquake ground motion and their implications: a numerical study
Effects of complicated 3‐D rupture geometries on earthquake ground motion and their implications: a numerical study
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复杂 3D 破裂几何形状对地震地面运动的影响及其含义：数值研究
DOI：
10.1111/j.1365-246x.2007.03627.x
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发表时间：
2008
影响因子：
2.8
通讯作者：
F. Gallovič
中科院分区：
文献类型：
--
作者：
M. Käser;F. Gallovič
摘要我们提出了一个数值研究的几何复杂的3-D破裂对近源地面运动的影响。在大多数运动学和动力学破裂模拟研究或地震矩张量和滑动反演中，都作出了完全平面断层的强烈假设。然而，从地质现场研究中得知，真实的断层迹线不是平面的，而是以相对较强的偏转、弯曲和其他不规则性为特征。在本文中，我们，调查的影响，这种非平面地震破裂地面运动模拟相比，其等效的平面。为了这个目的，我们应用高度精确的间断Galerkin方法，该方法能够通过一组不必与网格顶点重合的双偶点源来结合复杂的非平面破裂表面的几何形状。我们生成一组运动学破裂模型，其特征在于随机空间偏转与各种相关长度和均方根值。然后，这些偏转确定相关的空间走向和倾向的变化。我们发现，偏转破裂模型具有相同的地震矩张量作为完美的平面，但是，减少标量矩，我们纠正。在我们的建模方法的声音验证后，我们提出了在破裂附近计算的合成速度地震图的偏转的影响。我们观察到，这些几何不规则性不仅会导致高频效应，而且会在整个频带内强烈影响合成物。最后，我们详细讨论了我们的观察结果，并得出结论，正确纳入的几何性质，如当地的走向和倾角变化的破裂面是一个重要的问题。我们还讨论了一些地震学领域，如强震模拟或地震矩张量和滑动反演，这些结果可能会产生重大后果的可能影响。
SUMMARY We present a numerical study of the effects of geometrically complicated 3-D ruptures on near-source ground motions. In most of the kinematic and dynamic rupture modelling studies or seismic moment tensor and slip inversions the strong assumption of a perfectly planar fault is made. However, it is known from geological field studies that real fault traces are not planar but characterized by relatively strong deflections, bends and other irregularities. In this paper we, investigate the effects of such non-planar earthquake ruptures on ground motion modelling in comparison to their equivalent planar ones. For this purpose we apply the highly accurate Discontinuous Galerkin method that is capable of incorporating the geometry of complicated non-planar rupture surfaces by a set of double couple point sources that do not have to coincide with the mesh vertices. We generate a set of kinematic rupture models characterized by random spatial deflections with various correlation lengths and root mean square values. These deflections then determine the associated spatial strike and dip variations. We find that the deflected rupture models have the same seismic moment tensor as the perfectly planar one, however, with a reduced scalar moment, which we correct for. After a sound validation of our modelling approach, we present the effects of the deflections on synthetic velocity seismograms computed in the vicinity of the rupture. We observe that these geometrical irregularities do not just lead to high frequency effects but can strongly affect the synthetics in the whole frequency band. Finally, we discuss our observations in detail and conclude that the correct incorporation of the geometrical properties such as local strike and dip variations of the rupture surface is an important issue. We also discuss possible implications for some seismological fields, such as strong-motion simulations or seismic moment tensor and slip inversions, where these results might have significant consequences.