Inversion of Longer‐Period OBS Waveforms for P Structures in the Oceanic Lithosphere and Asthenosphere
Inversion of Longer‐Period OBS Waveforms for P Structures in the Oceanic Lithosphere and Asthenosphere
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大洋岩石圈和软流圈 P 结构长周期 OBS 波形反演
DOI：
10.1029/2019jb018810
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Utada Hisashi
中科院分区：
文献类型：
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作者：
Takeuchi Nozomu;Kawakatsu Hitoshi;Shiobara Hajime;Isse Takehi;Sugioka Hiroko;Ito Aki;Utada Hisashi
我们对部署在西北太平洋的宽带海底地震仪 (BBOBS) 记录的 P 波形进行了波形反演。因此，揭示了以前的表面波或接收函数分析未能很好解决的海洋上地幔速度的深度剖面。我们考虑了岩石圈中的方位各向异性，这使得方差减少从 34% 显着提高到 44%。由此产生的 P 模型在岩石圈和软流圈中分别表现出较高和较低的速度。发现速度对比度是先前模型中观察到的速度对比度的第二/三分之一；然而，获得的模型似乎与源附近的 VS 结构有一些权衡。我们将我们的 P 模型与之前使用 BBOBS 获得的 S 模型进行比较，并获得了 VP/VS 模型。由此产生的 VP/VS 模型有两个显着特征。首先，岩石圈的特点是 VP/VS 值随深度快速增加，这意味着化学分层。其次，岩石圈-软流圈边界（LAB）附近的 VP/VS 值大于考虑非谐效应预测的任何主要上地幔矿物的合成值，这表明滞弹性或熔融的影响。
We performed waveform inversion of thePwaveforms recorded by our BroadBand Ocean Bottom Seismometers (BBOBSs) deployed in the Northwestern Pacific. Consequently, the depth profile of thePvelocity of the oceanic upper mantle, which has not been well resolved by previous surface wave or receiver function analyses, was revealed. We considered the azimuthal anisotropy in the lithosphere, which significantly improved the variance reduction from 34%to 44%. The resultingPmodel exhibited higher and lower velocities in the lithosphere and asthenosphere, respectively. The velocity contrast was found to be second/third of that observed in the previousSmodels; however the obtained model appeared to have some trade‐off with theVSstructures in the vicinity of the source. We compared ourPmodel with the previousSmodel obtained using our BBOBSs and obtained theVP/VSmodel. The resultingVP/VSmodel has two notable features. First, the lithosphere is characterized by a rapid increase in theVP/VSvalues with depth, which implies chemical stratification. Second, theVP/VSvalues in the vicinity of the lithosphere‐asthenosphere boundary (LAB) are larger than the synthetic values of any major upper mantle mineral predicted by considering the anharmonic effects, which suggests the effects of anelasticity or melt.