Rapid directivity detection by azimuthal amplitude spectra inversion
Rapid directivity detection by azimuthal amplitude spectra inversion
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DOI：
10.1007/s10950-010-9217-4
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发表时间：
2011-01-01
影响因子：
1.6
通讯作者：
Dahm, Torsten
中科院分区：
文献类型：
--
作者：
Cesca, Simone;Heimann, Sebastian;Dahm, Torsten
早期检测破裂方向性的存在对于正确估计与地震发生相关的地面运动和风险起着重要作用。我们在这里提出了一种快速检测破裂方向性的简单方法，该方法还可用于区分断层和辅助平面，并首次估计重要的运动源参数，例如破裂长度和破裂时间。我们的方法基于纵波地震图振幅谱的反演，以推导出每个台站的视在持续时间，并对其方位角行为进行连续建模。假设空间点源近似建立合成波形，并且空间点源的有限视在持续时间根据破裂方向性来解释。由于点源的合成地震图的计算速度非常快，因此一旦推导出震源机制，就可以在几秒钟内检测到方向性的存在。该方法首先使用线源和平面源的合成数据集进行测试，然后成功应用于希腊伯罗奔尼撒半岛最近发生的 6.2-6.8 级浅层地震。该方法适合自动化应用，并且可用于改进运动波形建模方法。
An early detection of the presence of rupture directivity plays a major role in the correct estimation of ground motions and risks associated to the earthquake occurrence. We present here a simple method for a fast detection of rupture directivity, which may be additionally used to discriminate fault and auxiliary planes and have first estimations of important kinematic source parameters, such as rupture length and rupture time. Our method is based on the inversion of amplitude spectra from P-wave seismograms to derive the apparent duration at each station and on the successive modelling of its azimuthal behaviour. Synthetic waveforms are built assuming a spatial point source approximation, and the finite apparent duration of the spatial point source is interpreted in terms of rupture directivity. Since synthetic seismograms for a point source are calculated very quickly, the presence of directivity may be detected within few seconds, once a focal mechanism has been derived. The method is here first tested using synthetic datasets, both for linear and planar sources, and then successfully applied to recent Mw 6.2-6.8 shallow earthquakes in Peloponnese, Greece. The method is suitable for automated application and may be used to improve kinematic waveform modelling approaches.