通过叠加sP前驱波研究汤加-斐济俯冲区"410"速度间断面起伏

The topography of the “410” provide an important constraint for understanding geodynamics、geochemistry and mineralogy. The deep telesismic earthquakes (depth>450km) occurred in Tonga-Fiji were recorded by Gansu Digital Seismic Network and China Earthquake Networks Center. Using these seismic observation waveforms we can stack precursor s410P produced by deep focus earthquakes that result from near-source, underside reflection off “410”, and compute “410” depth using of the differential travel time between sP and its precursor s410P near Tonga-Fiji subduction zone. It is possible to get the fine topography of the “410” in the Tonga-Fiji subduction zone. On the basis of the “410” topography, we will further discuss the character of “410” and the influence of subduction slab on shape variation of “410”. This research has great scientific significance for us to recognize the complex structure of subduction zones and objective understanding the dynamic process of the deep part of the Earth.

“410”速度间断面的起伏为正确理解地球动力学、地球化学和矿物物理学提供了重要的约束。利用甘肃省数字测震台网以及中国地震台网中心（2000-2015）记录到的发生于汤加-斐济地区震源深度大于450km的深震资料，使用倾斜叠加方法对深震震相sP在近源区“410”速度间断面底界面反射的前驱波s410P做叠加，通过sP与其前驱波s410P的到时差计算汤加-斐济俯冲区410-km间断面的深度，获得410-km速度间断面的精细起伏，进一步探讨“410”速度间断面的性质及其俯冲带对其形态变化的影响。本研究的开展对于认识俯冲区的复杂结构、正确理解地球深部的动力学过程具有重要的科学意义。

“410”速度间断面的起伏为正确理解地球动力学、地球化学和矿物物理学提供了重要的约束。本项目利用了中国地震台网中心（2008-2017）记录到的发生于汤加-斐济地区震源深度大于450 km的深震资料，使用倾斜叠加方法有效提取了近源区“410”速度间断面底界面反射的前驱波s410P，通过sP与其前驱波s410P的到时差计算汤加-斐济俯冲区“410”速度间断面的深度，获得了“410”速度间断面底界面反射的37个反射点的位置，得到“410”速度间断面的精细起伏。结果表明：汤加-斐济俯冲区“410”速度间断面变化范围在415 - 435 km之间，平均深度为425 km；北部深，中部变化复杂，南部较深，并且变化较小，汤加-斐济地区的“410”速度间断面呈现出非常复杂的特征。本研究的开展对于认识俯冲区的复杂结构、正确理解地球深部的动力学过程具有重要的科学意义。