Small-scale heterogeneities in the oceanic lithosphere inferred from guided waves
Small-scale heterogeneities in the oceanic lithosphere inferred from guided waves
复制标题
从导波推断海洋岩石圈的小尺度异质性
DOI：
10.1002/grl.50330
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
and A. Ito
中科院分区：
文献类型：
--
作者：
Shito;A.;D. Suetsugu;T. Furumura;H. Sugioka;and A. Ito
我们分析了日本下方俯冲板片中发生的深源地震的地震波形，这些地震波形是由安装在西北太平洋海底的宽带海底地震仪（BBOBS）记录的。数据显示波形具有低频直接 P 起始，随后是大振幅、高频、长持续时间的 Po 和 So 波。通过对BBOBS记录的分析和地震波传播的数值有限差分法模拟，我们阐明了这种导波的产生和传播过程。我们证明了低频直接 P 波和 S 波在软流圈中传播，随后的高频、长持续时间 Po 和 So 波是由 P 波和 S 波的多次前向散射产生的。散射的发生是由于海洋岩石圈俯冲部分和水平部分的横向拉长不均匀性，视速度（Vp= 8.1 km/s，Vs= 4.6 km/s）接近海洋岩石圈的速度。
We analyze seismic waveforms from deep‐focus earthquakes occurring in the subducting slab beneath Japan, recorded by broadband ocean bottom seismometers (BBOBSs) installed on the northwestern Pacific Ocean seafloor. The data reveal waveforms with a low‐frequency direct P onset, followed by large‐amplitude, high‐frequency, long‐duration Po and So waves. From the analysis of the BBOBS records and a numerical finite‐difference method simulation of seismic wave propagation, we elucidate the generation and propagation processes of such guided waves. We demonstrate that the low‐frequency direct P and S waves propagate in the asthenosphere and that the following high‐frequency, long‐duration Po and So waves are developed by multiple forward scattering of P and S waves. The scattering occurs due to laterally elongated heterogeneities in both the subducting and horizontal parts of the oceanic lithosphere, with the apparent velocities (Vp= 8.1 km/s, Vs= 4.6 km/s) being close to the velocities of oceanic lithosphere.