A Structural and Dynamic Model of Subduction at the Middle American Trench, Central Mexico

该项目正在通过数值实验探索俯冲带的动力学，促进俯冲带状态与其演化方式之间的概念和数量联系。动力学模型与沿中美洲海沟(MAT)的俯冲有关。MAT被用来约束依赖于时间的模型，因为自渐新世以来火山弧有明显的渐进式重新定向。有了模型，现今的地幔结构与古地理联系在一起。我们的分析研究与中美洲俯冲实验(MASE)不谋而合--这是墨西哥和美国科学家之间的一项重大国际合作。目前正在沿着从阿卡普尔科到坦皮科(穿过墨西哥城)的横贯墨西哥的横断面部署一项密集的地震实验，并为俯冲建模提供关键参数--板块几何和结构，以及地幔楔体粘度的地震代用。尽管板块年龄和俯冲速度沿板块的变化很小，但地球动力学模型的构建是由板块结构中沿走向的显著变化推动的。各种模型被用来解决一系列问题(包括，平板制度是如何开始的，上板块如何抵抗平板的变形，较年轻的板块如何具有陡峭的倾角，等等)。结构模型、瞬时地球动力学模型和依赖时间的地球动力学模型正在被整合成一个连续的套件，其中一个模型的结果正在改善另一个模型。该项目广泛利用了新建立的加州理工地球科学计算设施及其2048处理器戴尔超级计算机。一些主要模型包括以下几种。第一个是地震模型。使用接收函数、走时和衰减层析成像以及全波场模拟对地震数据进行分析，以了解地壳和板块结构以及地幔楔体的粘性结构。第二种是瞬时地球动力学模型。发现了与地震结构、热流、地形、重力和水平板的主要拉应力相一致的二维和三维粘性模型。目前正在进行确定，以确定哪些板块和地幔楔形粘性模型与这些结果一致。第三种是古地理上一致的地球动力学模型。平板俯冲的开始和墨西哥火山活动模式的时空变化正在用球面对流模型和交互式板块重建软件(GPlates)来处理。这项研究为博士后研究员弗拉德·马内亚提供了进一步发展他的研究生涯，特别是地球动力学的机会。该项目还支持对一名地球物理学研究生进行培训。这笔用于分析MASE数据的资金正在加强美国和墨西哥科学家之间的合作。

This project is advancing the conceptual and quantitative links between the state of subduction zones and the manner in which they evolve by exploring their dynamics with numerical experiments. Dynamic models are being related to subduction along the Middle America Trench (MAT). MAT is being used to constrain time-dependent models because of a clear progressive reorientation of the volcanic arc since the Oligocene. With models, present mantle structure is being linked with paleogeography. Our analysis study coincides with the Meso-American Subduction Experiment (MASE) -- a major international collaboration between Mexican and American scientists. A dense seismic experiment is currently deployed along a trans-Mexico transect from Acapulco to Tampico (through Mexico City) and provides critical parameters for subduction modeling -- the slab geometry and structure, and seismic proxies for viscosity of the mantle wedge. Construction of the geodynamic model is motivated by significant along-strike variations in slab structure despite simple variations in plate age and subduction velocity along the MAT. A variety of models are being brought to bear on a series of questions (including, how does the flat slab regime set in, how does the upper plate resist deformation by the flat slab, how can a younger plate have a steep dip, etc.). Structural, instantaneous geodynamic, and time-dependent geodynamic models are being integrated into a continuous suite in which the results of one are improving the others. This projects makes extensive use of the newly established Caltech Geosciences Computational Facility with its 2048 processor Dell Supercomputer. Some principal models include the following. The first are seismic models. Seismic data are being analyzed for crustal and slab structure and the viscosity structure of the mantle wedge using receiver functions, travel time & attenuation tomography, and full wavefield simulations. The second are instantaneous geodynamic models. Dynamic models are being found that are consistent with seismic structure, heat flow, topography, gravity and the dominate tensile stress of the horizontal slab with 2-D and 3-D viscous models. Determinations are underway to see what slab and mantle wedge viscosity models are consistent with these results. The third are paleogeographically consistent geodynamic models. The onset of flat slab subduction and the space-time changes in the pattern of Mexican volcanism are being addressed with a spherical convection model coupled to interactive plate reconstruction software (GPlates).This study is providing the opportunity for a postdoctoral researcher, Vlad Manea, to further his research career, particularly in geodynamics. The project also supports the training of one graduate student in geophysics. This funding for analysis of MASE data is enhancing collaboration between US and Mexican scientists.