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岩石圈软流圈边界(lithosphere-asthenosphere boundary,LAB)是上地幔内具有负速度梯度的地震间断面.开展对俯冲带区域LAB的地震学探测有助于进一步理解岩石圈与软流圈的相互作用以及与板块俯冲相关的地球动力学过程.本文收集了2002~2014年发生于伊豆-小笠原地区的3个深源地震(400~600 km)的垂向宽频带波形资料,利用线性倾斜叠加方法对波形数据进行处理后获得了相对走时-慢度域的灰度图和叠加波形图,并成功提取了s_P震相在LAB反射的前驱震相s_(LAB)P,该震相的极性与s_P相反,幅度比为0.17~0.21.基于改进的一维速度模型IASP91-IB计算获得了近源区6个s_(LAB)P震相反射点的分布.研究表明伊豆-小笠原岛弧下方LAB深度位于58~65 km,平均深度为62 km,起伏变化较小(7 km).与菲律宾海构造稳定地区研究结果相比,伊豆-小笠原岛弧地区海洋岩石圈出现了明显减薄的现象,其应与西太平洋俯冲板块在地球深部持续释放的挥发分物质导致了软流圈出现部分熔融以及弧后地幔楔内小尺度对流的强侵蚀作用密切相关.
The lithosphere-astosphere boundary (LAB) is a seismic cross-section with negative velocity gradient in the upper mantle, and the seismological exploration of LAB in the subducted zone helps to further understand the interaction between lithosphere and asthenosphere And the geodynamic processes associated with the plate subduction.This paper collects the vertical broadband waveform data of three deep-seated earthquakes (400-600 km) occurred in Izu-Ogasawara area from 2002 to 2014. By using the method of linear gradient superposition After processing the waveform data, the grayscale and superposition waveforms of relative traveltime-slowness domain are obtained, and the pre-excitation phase s_ (LAB) P of the s_P phase at the LAB reflection is successfully extracted. The polarity of the phase and In contrast, the amplitude ratio is 0.17-0.21. Based on the improved one-dimensional velocity model IASP91-IB, the distribution of the 6 s LAB particles in the near source region is obtained. The study shows that the LAB depth below the Izu-Ogasawara island arc Located between 58 km and 65 km with an average depth of 62 km and a small fluctuation (7 km) .Compared with the research results in the structural stability of the Philippine Sea, the oceanic lithosphere in the Izu-Ogasawa Island arc area shows a significant thinning, Should dive with the Western Pacific The persistent release of volatile matter from the deep Earth’s plate led to a close correlation between the partial melting of the asthenosphere and the strong erosion of small-scale convection within the mantle wedge after the arc.