Back‐Projection Imaging of a Tsunami Excitation Area With Ocean‐Bottom Pressure Gauge Array Data
Back‐Projection Imaging of a Tsunami Excitation Area With Ocean‐Bottom Pressure Gauge Array Data
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利用海底压力计阵列数据对海啸激发区进行反投影成像
DOI：
10.1029/2022jc018480
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Yomogida Kiyoshi
中科院分区：
文献类型：
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作者：
Mizutani Ayumu;Yomogida Kiyoshi
反投影方法由于其简单和低计算成本而被应用于地震学中的许多地震，并且它可以在没有任何特定先验信息的情况下估计复杂的断层破裂过程。在这项研究中，我们将反投影方法应用于使用海底压力计阵列观察到的海啸记录，并证明它是一种强大的新工具，而不是熟悉的波形反演。所获得的反投影图像与先前波形反演估计的初始海啸高度分布一致，其空间分辨率似乎更好。我们的结果表明，2016年福岛外地震的断层大小约为一半，与标准地震的标度律不同。目前的海啸反投影分析也可以估计早期海啸传播的特征。此外，估计的图像似乎是可靠的，即使在起源时间后30分钟，因此反投影分析将有助于早期检测海啸源的位置和空间范围。在目前的情况下，分析中可用的台站数量受到日本海沟附近高速区折射引起的海啸传播衍射的影响。换句话说，震源离海岸越远，可供分析的台站就越多。由于大多数海啸地震发生在俯冲轴或其外部隆起区域附近，因此反投影分析应该对大多数海啸地震的震源估计有效。
A back‐projection method has been applied to many earthquakes in seismology due to its simple and low computational cost, and it can estimate complex fault rupture processes without any specific a priori information. In this study, we applied the back‐projection method to the tsunami records observed using an ocean‐bottom pressure gauge array and demonstrated it to be a powerful new tool other than the familiar waveform inversion. The obtained back‐projection image was consistent with the initial tsunami height distributions estimated by previous waveform inversions, and its spatial resolution appeared to be even better. Our result suggests that the fault size of the 2016 Off‐Fukushima earthquake was about half, different from the scaling law of standard earthquakes. The present tsunami back‐projection analysis can also estimate the feature of early tsunami propagations. In addition, the estimated image seems to be reliable even 30 min after the origin time, so the back‐projection analysis will be useful in an early detection of the location and spatial extent of a tsunami source. In the present case, the number of available stations in the analysis was found to be affected by the diffraction of tsunami propagation caused by the refraction by a high velocity zone near the Japan Trench. In other words, the further the source is from the coast, the more stations to be analyzed are available. Since most tsunami‐generating earthquakes occur near the subduction axis or its outer‐rise region, the back‐projection analysis should be effective for source estimation of the majority of tsunami‐generating earthquakes.