【摘要】 本文首先利用甘肃数字测震台网和甘东南野外观测流动台阵记录的汤加—斐济俯冲带深震震相sP,使用倾斜叠加方法有效提取sP在近源区"410"速度间断面底界面反射的弱前驱波s410P;其次基于CRUST1.0修正的IASP91模型,通过震相sP与其前驱波s410P的到时差对比,给出了汤加—斐济俯冲带"410"速度间断面底部反射点的深度约为398.5km,抬升约11.5km,这与俯冲带与近源区"410"间断面的相互作用有关;最后得到了该区域新的地震波速度模型IASP91_Tonga.本文结果将对更好地认识该俯冲带的复杂结构、正确理解地球深部的动力学过程具有重要的参考价值.更多还原

【Abstract】 The sP seismic phase of the Tonga-Fiji subduction zone have a clear image in the Gansu Digital Seismic Network and southeastern Gansu temporary observation array.In this paper,we extracted the weak precursors s410 P by slant stack method,and the s410 P precursors are produced by deep focus earthquakes that result from near-source underside reflection off"410".We compute the depth of"410"discontinuity by using the differential travel time between sP and its precursor s410 P near Tonga-Fiji subduction zone based on the modified velocity model(IASP91_Tonga)in this zone based on CRUST1.0model.The depth of"410"discontinuity is about 398.5km,and uplifted about 11.5km,which maybe relate to the interaction of the subduction zone and the"410"discontinuity in the near-source zone.This result is of great significance to recognize the complex structure of subduction zones and objectively understand the dynamic process of the deep Earth.更多还原