Near-surface weakening in Japan after the 2011 Tohoku-Oki earthquake
Near-surface weakening in Japan after the 2011 Tohoku-Oki earthquake
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DOI：
10.1029/2011gl048800
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发表时间：
2011-09-02
影响因子：
5.2
通讯作者：
Snieder, R.
中科院分区：
文献类型：
--
作者：
Nakata, N.;Snieder, R.
2011年3月11日发生的9.0级地震是日本近代史上最大的地震之一。覆盖日本大部分地区的强震监测网KiK-net记录了主震前后地震活动引起的地面运动。通过反褶积的地震所产生的波形，记录在地面和在一个钻孔在KiK-净站FKSH 18，我们检测到剪切波速度的减少在上100米的约10%，和随后的愈合，随时间的推移而变化的曲线。利用2011年1月1日至2011年5月26日期间发生的300多次地震的所有可用钻孔和地面记录，我们观察到日本东北部发生东北冲地震后，上部几百米处的剪切波速度降低了约5%。速度降低的区域约为1,200公里宽，比先前报告的其他较大地震后速度降低的研究要宽得多。剪切波速度的降低表明，剪切模量和剪切强度在日本的大部分地区都有所降低。引文：Nakata，N.，和R. Snieder（2011），2011年东北冲地震后日本近地表弱化，地球物理学。保留信函：38，L17302，doi：10.1029/2011GL048800。
The magnitude (M-W) 9.0 Tohoku-Oki earthquake on 11 March 2011 was one of the largest in recent history. Ground motion caused by the seismicity around the time of the main shock was recorded by KiK-net, the strong-motion network that covers most of Japan. By deconvolving waveforms generated by earthquakes that are recorded at the surface and in a borehole at KiK-net station FKSH18, we detect a reduction of shear-wave velocity in the upper 100 m of about 10%, and a subsequent healing that varies logarithmically with time. Using all available borehole and surface records of more than 300 earthquakes that occurred between 1 January 2011 and 26 May 2011, we observe a reduction in the shear-wave velocity of about 5% in the upper few hundred meters after the Tohoku-Oki earthquake throughout northeastern Japan. The area of the velocity reduction is about 1,200 km wide, which is much wider than earlier studies reporting velocity reductions following other larger earthquakes. The reduction of the shear-wave velocity is an indication that the shear modulus, and hence the shear strength, is reduced over a large part of Japan. Citation: Nakata, N., and R. Snieder (2011), Near-surface weakening in Japan after the 2011 Tohoku-Oki earthquake, Geophys. Res. Lett., 38, L17302, doi:10.1029/2011GL048800.