Two-dimensional resonances in Alpine valleys identified from ambient vibration wavefields
Two-dimensional resonances in Alpine valleys identified from ambient vibration wavefields
复制标题
从环境振动波场识别高山山谷中的二维共振
DOI：
10.1111/j.1365-246x.2006.02935.x
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发表时间：
2006
影响因子：
2.8
通讯作者：
D. Giardini
中科院分区：
文献类型：
--
作者：
D. Roten;D. Fäh;C. Cornou;D. Giardini
摘要 尽管数值模拟长期以来一直显示二维共振在沉积物填充山谷场地效应估计中的重要性，但当前的危害评估技术通常不考虑这种现象。我们提出了一种通过分析密集阵列上同时记录的环境噪声来识别典型高山山谷共振行为的方法。使用当前 3D 数值模拟技术获得的合成环境噪声进一步评估了该方法的适用性。利用参考站法从实测数据中识别出基模SV以及SH基模和第一高模的谐振频率，验证了前人的研究结果。从观察到的和合成的噪声中获得的频谱幅度和相位行为的模式与二维共振的预期特性密切相关。频率波数技术的应用表明，噪声波场以低频（0.25 至 0.50 Hz）的驻波为主。不同的二维共振模式在水平与垂直光谱比中产生突出的峰值，这不能用一维共振来解释。我们得出的结论是，在垂直于谷轴的线性阵列上同时测量的环境噪声记录可用于识别充满沉积物的山谷中的共振模式。
SUMMARY Although numerical simulations have for long shown the importance of 2-D resonances in site effect estimations of sediment-filled valleys, this phenomenon is usually not taken into account by current hazard assessment techniques. We present an approach to identify the resonance behaviour of a typical Alpine valley by analysis of ambient noise recorded simultaneously on a dense array. The applicability of the method is evaluated further using synthetic ambient noise acquired with current 3-D numerical simulation techniques. Resonance frequencies of the fundamental mode SV and the fundamental and first higher mode of SH are identified from measured data with the reference station method, verifying results of previous studies. Patterns of spectral amplitude and phase behaviour obtained from observed and synthetic noise correlate well with properties expected for 2-D resonance. Application of a frequencywavenumber technique shows that the noise wavefield is dominated by standing waves at low frequencies (0.25 to 0.50 Hz). The different 2-D resonance modes are creating prominent peaks in horizontal-to-vertical spectral ratios, which can not be interpreted in terms of 1-D resonance. We conclude that ambient noise records measured simultaneously on a linear array perpendicular to the valley axis may be used for identification of resonance modes in sediment-filled valleys.