伊豆-小笠原地区岩石圈软流圈边界地震学证据

发布时间：2018-04-04 15:47

本文选题：岩石圈软流圈边界　切入点：伊豆-小笠原地区　出处：《科学通报》2017年07期

【摘要】：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.
[Abstract]:Lithosphere-asthenosphere boundary lithosphere-asthenosphere boundarylab) is an interseismic section with negative velocity gradient in the upper mantle.The seismological exploration of LAB in the subduction zone is helpful to further understand the interaction between lithosphere and asthenosphere and the geodynamic processes associated with plate subduction.In this paper, the vertical broadband waveform data of three deep source earthquakes occurring in the Yidou-Ogasawara area from 2002 to 2014 are collected.After processing the waveform data by linear tilt stacking method, the grayscale and superposition waveforms in the relative travel time and slowness domain are obtained, and the precursor phase of the SSP seismic phase in LAB reflection is extracted successfully. The polarity of the phase is opposite to that of sP, and the amplitude ratio is 0.17 ~ 0.21.Based on the improved one-dimensional velocity model (IASP91-IB), the distribution of the reflection points of six s_(LAB)P phases in the near source region has been obtained.The results show that the LAB depth below the Iso-Ogasawara island arc is located at 586km, the average depth is 62km, and the fluctuation is small.Compared with the results of the study on the structural stability of the Philippine Sea, the oceanic lithosphere in the Yidou-Ogasawara Island Arc area is obviously thinned.It is closely related to the release of volatile matter from the western Pacific subduction plate in the deep part of the earth, which leads to the partial melting of the asthenosphere and the strong erosion of small scale convection in the back-arc mantle wedge.
【作者单位】：中国科学院计算地球动力学重点实验室;中国科学院大学地球科学学院;
【基金】：国家自然科学基金(41274092,41474070)资助
【分类号】：P315.2

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