Many types of slow earthquakes have been discovered at subduction zones around the world. However, the physical process of these slow earthquakes is not well understood. To monitor offshore slow earthquakes, a marine seismic and geodetic experiment was conducted at the Hikurangi subduction margin from May 2014 to June 2015. During this experiment, a large slow slip event (Mw 6.8) occurred directly beneath the ocean bottom seismometer (OBS) network. In this study, S-wave splitting and polarization analysis methods, which have been previously used on onshore data to investigate tremor and anisotropy, are applied to continuous OBS waveform data to identify tremors that are too small to detect by the envelope cross correlation method. Continuous tremor activity with stable polarization directions is detected at the end of the 2014 slow slip event and continued for about 2 weeks. The tremors are generated around a southwest bend in the slow slip contours and at the landward edge of a subducted seamount. Our findings corroborate a previous interpretation, based on burst-type repeating earthquakes and intermittent tremor, that localized slow slip and tremor around the seamount was triggered by fluid migration following the large plate boundary slow slip event and indicate tremor occurred continuously rather than as isolated and sporadic individual events.

中文翻译：

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新西兰近海 Hikurangi 俯冲边缘 2014 年大型慢滑事件后具有稳定极化方向的持续震颤活动

在世界各地的俯冲带发现了许多类型的慢地震。然而，这些慢地震的物理过程尚不清楚。为监测近海慢地震，2014 年 5 月至 2015 年 6 月在 Hikurangi 俯冲边缘进行了海洋地震和大地测量实验。在该实验期间，在海底地震仪 (OBS) 网络正下方发生了大型慢滑事件 (Mw 6.8) . 在本研究中，将先前用于陆上数据研究震颤和各向异性的 S 波分裂和极化分析方法应用于连续 OBS 波形数据，以识别太小而无法通过包络互相关法检测的震颤。在2014年慢滑事件结束时检测到具有稳定极化方向的连续震颤活动，并持续了约2周。地震发生在缓慢滑动等值线的西南弯附近和俯冲海山的陆地边缘。我们的研究结果证实了先前基于爆发型重复地震和间歇性震颤的解释，即海山周围的局部慢滑和震颤是由大板块边界慢滑事件后的流体迁移触发的，并表明震颤是连续发生的，而不是孤立的和零星的个别事件。