Earthquake nucleation and fault slip complexity in the lower crust of central Alaska
Earthquake nucleation and fault slip complexity in the lower crust of central Alaska
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DOI：
10.1038/s41561-018-0144-2
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发表时间：
2018-06
影响因子：
18.3
通讯作者：
C. Tape;S. Holtkamp;V. Silwal;J. Hawthorne;Y. Kaneko;J. Ampuero;C. Ji;N. Ruppert;Kyle Smith;M. West
中科院分区：
文献类型：
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作者：
C. Tape;S. Holtkamp;V. Silwal;J. Hawthorne;Y. Kaneko;J. Ampuero;C. Ji;N. Ruppert;Kyle Smith;M. West
地震是在很大程度上未知的条件下开始的。在实验室模拟实验和连续介质模型中，地震从缓慢滑动、成长成核向快速滑动破裂转变。在自然界中，地震通常是突然开始的，没有证据表明有成核过程。在这里，我们报告了阿拉斯加中部走滑断裂带扩大地震成核和极低频率地震(VLFE)的证据，这种现象以前只在俯冲带环境中报道过。2016年，VLFE转变为3.7级地震，并在此之前发生了长达12小时的加速前震序列。利用部署在震中30 公里范围内的12个地震台，我们识别出了22 S成核期间明显的高频和低频波的重合辐射。通过一个从扩展的慢滑移前沿附近辐射高频波的模型，定量地预测了成核信号的幂函数时间增长。这些观测揭示了阿拉斯加中部走滑断裂系统孕震带底部附近滑动过程的连续性和复杂性。
Earthquakes start under conditions that are largely unknown. In laboratory analogue experiments and continuum models, earthquakes transition from slow-slipping, growing nucleation to fast-slipping rupture. In nature, earthquakes generally start abruptly, with no evidence for a nucleation process. Here we report evidence from a strike-slip fault zone in central Alaska of extended earthquake nucleation and of very-low-frequency earthquakes (VLFEs), a phenomenon previously reported only in subduction zone environments. In 2016, a VLFE transitioned into an earthquake of magnitude 3.7 and was preceded by a 12-hour-long accelerating foreshock sequence. Benefiting from 12 seismic stations deployed within 30 km of the epicentre, we identify coincident radiation of distinct high-frequency and low-frequency waves during 22 s of nucleation. The power-law temporal growth of the nucleation signal is quantitatively predicted by a model in which high-frequency waves are radiated from the vicinity of an expanding slow slip front. The observations reveal the continuity and complexity of slip processes near the bottom of the seismogenic zone of a strike-slip fault system in central Alaska.