Tidal Modulation and Tectonic Implications of Tremors in Taiwan
Tidal Modulation and Tectonic Implications of Tremors in Taiwan
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DOI：
10.1029/2018jb015663
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发表时间：
2018-07
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影响因子：
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通讯作者：
Kate Huihsuan Chen;H. Tai;S. Ide;T. Byrne;C. Johnson
中科院分区：
文献类型：
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作者：
Kate Huihsuan Chen;H. Tai;S. Ide;T. Byrne;C. Johnson
我们提出了在欧亚大陆地壳与菲律宾海板块碰撞形成碰撞造山带的大陆俯冲带6年的震颤观测结果。2007年至2012年期间，共发现和定位了1893次持续时间在60秒至2216秒之间的震颤事件。对震颤时间的频谱分析揭示了几个与半年、半日和日成分相关的尖锐峰值，表明强烈的潮汐和季节调制。当潮汐应力和应力率与地震活动比较时，我们发现地震事件的超额次数百分比随剪应力和拉应力的振幅而增加，而不随剪应力率而增加。在3.5 kPa时，当剪应力最大时，超出的百分比平均值达到150%。这种与潮汐切应力的高度相关性与潮汐记录的观测结果一致，其中76-82%的地震发生在东海岸验潮站高于中位水位的位置。在空间上，在碰撞造山带南部，欧亚大陆地壳在此发生了俯冲、变质和叠瓦作用，在深度15 ~ 45 km处形成了一个陡峭的、东南倾斜的椭球状构造。我们为震颤带提出了一个弱断层模型，该模型代表了地壳深处脆韧性剪切带的开始或重新激活，并协调了先前不同研究中提出的陡倾和缓倾断层几何形状。
We present results from 6 years of tremor observations in a continental subduction zone where the continental crust of Eurasia is colliding with the Philippine Sea Plate, forming a collisional orogen. During 2007–2012, 1,893 tremor events with durations ranging from 60 to 2,216 s were identified and located. Spectral analysis of the tremor times reveals several sharp peaks that correlate with the semi annual, semidiurnal, and diurnal constituents, indicating a strong tidal and seasonal modulation. When the tidal stresses and stressing rates are compared with tremor activities, we find that the percent excess number of events increases with amplitude of shear stress and tensile stress but not with shear stressing rate. The percent excess reaches a mean value of 150% for highest shear stress at 3.5 kPa. Such high correlation with tidal shear stress is consistent with the observation from tidal records, where 76–82% of tremors occurred at higher than the median water level at tide gauge stations on the east coast. Spatially, the ambient tremors appear to form a steep, southeast dipping ellipsoidal structure at depths of 15 to 45 km in the southern part of the collisional orogen where the continental crust of Eurasia has been subducted, metamorphosed, and imbricated. We propose a weak fault model for the tremor zone that represents the initiation or reactivation of a brittle‐ductile shear zone deep in the crust and reconciles both the steeply dipping and gently dipping fault geometries proposed previously from different studies.