Ten-second Love-wave propagation and strong ground motions
Ten-second Love-wave propagation and strong ground motions
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DOI：
10.1029/98jb00613
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发表时间：
1998-09
期刊：
影响因子：
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通讯作者：
Chau-Huei Chen;T. Teng;Y. Gung
中科院分区：
文献类型：
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作者：
Chau-Huei Chen;T. Teng;Y. Gung
本文应用高斯波束面波方法，研究了台湾地区地壳非均匀性明显的区域，特别是震中距大于几个震源深度的区域，短周期（10 s）面波的产生和传播，其中高频近场运动被极大地衰减并且表面波被充分地发展。通过扰动源模型以及地壳模型在迭代反演过程中，我们已经取得了一个很好的适合最近的强震观测记录在台湾东澳地震（1994年6月5日，ML = 6.0）。这使我们能够（1）从最近的层析成像结果得到的初始模型中获得台湾的三维地壳模型，更重要的是，（2）解释历史大地震强度图中报告的强震分布模式，并预测台湾未来大地震的长周期强震分布模式。通过改进的三维结构，我们可以更好地了解短周期面波传播，因为它们被地壳横向非均匀性所修改。聚焦和散焦被清楚地展示。特别值得注意的是中央山脉，一个巨大的第三纪变质体形成台湾的脊梁，似乎是传播表面波的"发散透镜"，而台湾西南部的大型沉积盆地似乎是波前的焦点。由于横向不均匀性传播的面波场的计算失真正确地反映了观测。
Applying the surface-wave Gaussian beam method to a three-dimensional (3-D) structure of Taiwan, we have studied the generation and propagation of short-period (10-s) surface waves in a region of pronounced crustal heterogeneity, especially in a region defined to be at an epicentral distance larger than a few focal depths away, where high-frequency near-field motions are largely attenuated and surface waves are adequately developed. By perturbing the source model as well as the crustal model in an iterative inversion process, we have achieved an excellent fit to the recent strong-motion observations recorded during the Tung-Ao earthquake (June 5, 1994, ML = 6.0) in Taiwan. This allows us to (1) obtain a refined 3-D crustal model of Taiwan from an initial model that was derived from recent tomographic results and, more important, (2) explain the distribution patterns of the strong shaking reported in terms of intensity maps for historical large earthquakes, and predict the long-period strong-motion distribution patterns for future large earthquakes in Taiwan. With an improved 3-D structure, we have gained better insight into short-period surface-wave propagations as they are modified by crustal lateral heterogeneity. Focusing and defocusing are clearly demonstrated. Of particular interest is the Central Mountain Range, a massive Tertiary metamorphic body forming the backbone of Taiwan, that seems to serve as a “divergent lens” for the propagating surface waves, whereas the large sedimentary basin in southwestern Taiwan seems to focus the wavefronts instead. The computed distortions of the propagating surface-wave field due to lateral heterogeneity are correctly reflected by the observations.