Seismic structure of subducted oceanic crust near the slow-earthquake source region in the southern Ryukyu arc
Seismic structure of subducted oceanic crust near the slow-earthquake source region in the southern Ryukyu arc
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琉球弧南部慢震震源区附近俯冲洋壳的地震结构
DOI：
10.1186/1880-5981-66-96
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
M. Nakamura
中科院分区：
文献类型：
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作者：
M. Nakamura
通过地震层析成像和接收函数分析，研究了琉球岛弧南部地区的板片结构与每两年重复一次的慢滑移事件发生之间的关系。为了计算接收函数，选取了212次6.0级以上的远震地震，并使用两台短周期地震仪和一台宽带地震仪观测了远震波形。假设接收器函数中的每个后期相位都是在深度处从 P 转换为 S 的波，则使用参考速度模型将时域接收器函数沿每个射线路径转换为深度域。由日本气象厅 (JMA) 手动选择的 P 波和 S 波到达时间用于地震层析成像分析。总共使用了 2002 年 1 月至 2014 年 3 月期间的 6,750 次地震。结果表明，板片地震群分布在板块界面以下约10公里处。这表明板片地震发生在板片内大洋莫霍面附近的洋壳下部。此外，慢滑移事件的断层与板块界面相对应。结果还表明，低Vp和高Vp/Vs区域分布在与慢滑事件相关的断层下方的俯冲洋壳内。这些结构与东海地区的结构相似，这表明琉球岛弧南部的热条件与发生慢滑移事件的热板区的情况相似。
Seismic tomography and receiver function analysis were carried out to investigate the relation between the slab structure in the southern Ryukyu arc region and the occurrence of slow-slip events that repeat biannually. For calculation of the receiver function, 212 teleseismic earthquakes with magnitudes larger than 6.0 were selected, and teleseismic waveforms were observed using two short-period seismometers and one broadband seismometer. Assuming that each later phase in a receiver function was a wave converted from P to S at depth, the time-domain receiver function was transformed into depth domain along each ray path using a reference velocity model. P- and S-wave arrival times, selected manually by the Japan Meteorological Agency (JMA), were used for the analysis of seismic tomography. In all, 6,750 earthquakes from January 2002 to March 2014 were used. The results showed that a cluster of slab earthquakes is distributed about 10 km below the plate interface. This suggests that the slab earthquakes occur in the lower part of the oceanic crust near the oceanic Moho within the slab. Moreover, the fault of the slow-slip events corresponds with the plate interface. The results also showed that a low Vp and high Vp/Vs area is distributed within the subducted oceanic crust underlying the fault associated with the slow-slip events. These structures are similar to those in the Tokai district, which suggests that the thermal condition of the southern Ryukyu arc is similar to the case of a hot-slab area where slow-slip events occur.