Smooth and rapid slip near the Japan Trench during the 2011 Tohoku-oki earthquake revealed by a hybrid back-projection method
Smooth and rapid slip near the Japan Trench during the 2011 Tohoku-oki earthquake revealed by a hybrid back-projection method
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DOI：
10.1016/j.epsl.2012.08.018
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发表时间：
2012-11
影响因子：
5.3
通讯作者：
Y. Yagi;A. Nakao;A. Kasahara
中科院分区：
文献类型：
--
作者：
Y. Yagi;A. Nakao;A. Kasahara
我们开发了一种新的反投影方法，该方法使用超声波P波形将直接P相位与震源附近结构面的反射相位进行积分，并使用该方法估计2011年东北冲地震的地震能量释放的时空分布。我们将观测波形与相应的绿色函数的归一化互相关投影到震源区，以获得地震能量释放的高分辨率图像。将该方法应用于2011年日本东北冲地震的P波波形数据，得到了低频和高频两个频段的地震能量释放时空分布。我们表明，在倾角方向上辐射的能量是强烈的频率依赖性。主要的高频地震辐射区域仅从震源向下延伸，而主要的低频地震辐射区域从震源向下和向上传播。当我们只使用低频数据集时，我们在日本海沟附近的最大滑动区域检测到大量地震能量的释放，该区域也是巨大海啸的震源区域。这个大的地震能量释放的时间对应于日本海沟附近的平滑和快速滑动的插曲，并反映了输入波形数据集的频带上获得的地震能量分布的强烈依赖性。平滑而快速的滑动可能是2011年东北冲地震震源区几乎所有累积弹性应变释放的触发因素。
We developed a new back-projection method that uses teleseismic P-waveforms to integrate the direct P-phase with reflected phases from structural discontinuities near the source and used it to estimate the spatiotemporal distribution of the seismic energy release of the 2011 Tohoku-oki earthquake. We projected a normalized cross-correlation of observed waveforms with corresponding Green's functions onto the seismic source region to obtain a high-resolution image of the seismic energy release. Applying this method to teleseismic P-waveform data of the 2011 Tohoku-oki earthquake, we obtained spatiotemporal distributions of seismic energy release for two frequency bands, a low-frequency dataset and a high-frequency dataset. We showed that the energy radiated in the dip direction was strongly frequency dependent. The area of major high-frequency seismic radiation extended only downdip from the hypocenter, whereas the area of major low-frequency seismic radiation propagated both downdip and updip from the hypocenter. We detected a large release of seismic energy near the Japan Trench in the area of maximum slip, which was also the source area of the gigantic tsunami, when we used only the low-frequency dataset. The timing of this large seismic energy release corresponded to an episode of smooth and rapid slip near the Japan Trench, and reflects the strong dependence of the seismic energy distribution obtained on the frequency band of the input waveform dataset. The episode of smooth and rapid slip may have been the trigger for a release of roughly all of the accumulated elastic strain in the seismic source region of the 2011 Tohoku-oki earthquake.