太平洋俯冲滞留板片与阿巴嘎火山关联性的地震探测研究

The genesis of Cenozoic continental basalts in Eastern China is highly debated. It has been advocated that the source of the Abaga magma in Northeast China was most likely related to the contribution of the fluids released from the stagnant Pacific slab in the mantle transition zone; however, The Daxin’anling–Taihang Gravity Lineament is the corresponding surface position corresponding to the western edge of the stagnant subducted Pacific slab revealed by seismic tomography. To investigate the spatial extent of the effect of Pacific subduction on the mantle characteristics of Eastern China, this project will install a small-aperture dense seismic array consisting of 56 broadband stations in central and eastern Inner Mongolia for one year. Combined with all available data from portable seismic array and permanent network, we are able to use receiver function method with common-conversion-point stacking technique to image the structure of the mantle transition zone. The waveform modeling of regional triplication phases and receiver function synthetic studies could further constraint the geometry of the subducting Pacific slab and its velocity perturbation. And we would have integrated observational constraints on seismic anisotropy from the splitting of shear waves, the character of P-to-S conversions, and the surface wave. These would help us to isolate anisotropy in different parts of crustal and mantle should result in tighter constraints on anisotropic geometry. Our observations of seismic anisotropy could provide relatively direct constraints on mantle dynamics because of the link between deformation and the resulting anisotropy, and improved our understanding of the crust-mantle coupling relationship and deep subduction processes beneath Northeast China. Then we are able to more definitively answer fundamental question concerning the involvement of subducted Pacific slab in the production of Northeast China basalts.

针对有迹象显示的太平洋俯冲滞留板片可能延伸到了大兴安岭–太行山重力梯度带，及重力梯度带以西中国东部面积最大的阿巴嘎火山与太平洋板块俯冲作用的争议问题，本研究将在地震资料覆盖度薄弱的内蒙古中东部，通过加密观测的宽频带流动地震探测剖面获取多方位覆盖的地震资料。充分利用固定地震台网和流动台阵多年累积的地震观测波形，通过接收函数的三维偏移成像和波形模拟研究，并结合三重震相对地幔转换带结构的有效观测约束，对太平洋俯冲滞留板片在地幔转换带的精确形态进行系统的追踪成像；通过S波、SKS波和Ps转换波来提取地壳和上地幔各向异性信息，结合地震面波各向异性结果来获取研究区深部不同层位变形的可靠信息。以直接的观测资料和客观论据，结合地球化学和地质学的研究成果，探讨研究区的壳幔流变性及太平洋板块俯冲与阿巴嘎火山活动的成因关联性，增进对俯冲过程与中国大陆构造演化的认识，为“中国区域地震学参考模型”构建提供支撑约束。

针对有迹象显示的太平洋俯冲滞留板片可能延伸到了大兴安岭–太行山重力梯度带，及重力梯度带以西中国东部面积最大的阿巴嘎火山与太平洋板块俯冲作用的争议问题，本研究计划在地震资料覆盖度薄弱的内蒙古中东部，通过加密观测的宽频带流动地震探测剖面获取多方位覆盖的地震资料。计划利用固定地震台网和流动台阵多年累积的地震观测波形，通过接收函数分析追踪太平洋俯冲滞留板片精细形态的研究工作，结合接收函数和地震各向异性等分析结果探讨太平洋俯冲对中国东北内陆火山的动力作用，增进对俯冲过程与中国大陆构造演化的认识。.本项目在全球最适宜于观测板块俯冲滞留在地幔转换带而地震资料覆盖稀疏的内蒙古中东部地区，完成了申请计划中的56个流动地震台阵延续观测一年任务，获取了多方位覆盖的地震资料，为西太平洋板块俯冲与地球深部过程及岩浆活动浅部响应等研究提供了良好的地震学约束资料。.本研究利用布设在我国东北地区的多期流动地震台以及国家固定地震台网数据，通过多种地震学研究，清晰地展现了由日本海沟至中国东北的太平洋俯冲板片整体活动图像，获得了太平洋板块俯冲滞留在我国东北地幔过渡带的俯冲界面成像结果，揭示了兴蒙造山带南部的岩石圈间断面（地壳Moho面、岩石圈–软流圈界面LAB和中岩石圈不连续面MLD）差异变化特征。结合接收函数和地震各向异性等分析结果探讨了太平洋俯冲对中国东北内陆火山的动力作用，分析认为晚新生代阿巴嘎和达里诺尔火山的活动很可能体现了正在发生的岩石圈局域改造过程，与停滞在地幔过渡带的太平洋板块俯冲前缘所触发的热物质上涌有关。研究表明太平洋俯冲滞留板片抵达大兴安岭–太行山重力梯度带附近，大兴安岭–太行山重力梯度带是太平洋板块俯冲动力影响的西边界。.本项目已在高影响因子刊物上发表9篇论文，其中SCI收录期刊论文6篇，还有1篇第一标注论文已完成小修后返回NI和SCI收录的Geophysical Research Letters期刊。