Structure and Deformation of the Crust and Upper Mantle Beneath SE Tibet

西藏东南部地壳和上地幔的结构和变形

• 批准号: 0910618
• 负责人: Robert van der Hilst
• 金额: --
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0910618&HistoricalAwards=false
• 关键词: Structure; Deformation; Crust; Upper; Mantle

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The main objective of our research is to improve our understanding of the structure and deformation of Earth?s crust and lithospheric mantle beneath SE Tibet using new seismic data and methods. From a geological perspective, the region between Sichuan basin and the eastern Himalaya Syntaxis is important for two reasons. First, as the southern end of the trans-China seismic belt it is among the most seismically active regions of continental SE Asia. The devastating 12 May 2008 earthquake in western Sichuan province, which caused massive loss of human life and damage to property and nature, is a grim reminder of this fact. Second, this is a critical region for understanding the post-collision evolution and eastward expansion of the Tibetan plateau. Under an expired Continental Dynamics grant we deployed 25 broadband seismometers in SE Tibet (08/2003-09/2004). Tomographic inversion for crustal structure of the data from this array has revealed widespread low velocity (and presumably mechanically weak) zones. These zones may control deformation and seismicity in the region, but their nature, 3-D structure and interconnectivity, and importance for seismogenesis on active faults are not yet well known. In 2006 the China Earthquake Administration installed in the same region an array of 300 broadband (Güralp) sensors, and this data is available to us for the purpose of our project. The analysis of CEA data will be conducted at the Institute of Geology (CEA, Beijing). This Sino-US collaboration, which will involve a graduate student and post-doc at MIT as well as students and research staff at CEA, gives an unprecedented opportunity to study the heterogeneity and anisotropy of the lithosphere and improve our understanding of the seismo-tectonics and hazard of a densely populated region that was recently hit by a devastating earthquakeEstablishing the connection between shallow and deep structures and the relationship between regional processes and localized seismicity requires multi-scale seismic imaging of heterogeneous, anisotropic lithosphere. We can meet this challenge by building on recent advances in data analysis (ambient noise interferometry), methodology (Eikonal and finite-frequency tomography), and the availability of spectacular array data (CEA). As a logical first step we will add (short period) data from the (densely spaced) CEA array to resolve (shallow) crustal heterogeneity and (azimuthal) anisotropy (both for Rayleigh and Love waves). This will give much new insight into crust structure in relation to seismicity. To improve resolution further we will combine interferometry with full wave inversion. We take a hierarchical approach. We first consider an asymptotic method (Eikonal tomography) to create a 3D starting model for subsequent full-wave (adjoint) tomography (with 3D finite frequency kernels). SEM synthetics will be used for quantitative model evaluation and validation. The proposed combination of noise interferometry and finite frequency tomography can also be applied to data from, for instance, USArray.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。我们研究的主要目标是提高我们对地球结构和变形的理解。利用新的地震资料和方法研究了西藏东南部的地壳和岩石圈地幔。 从地质学的角度来看，四川盆地和东喜马拉雅构造结之间的区域是重要的，原因有二。 首先，作为横贯中国地震带的南端，它是东南亚大陆地震最活跃的地区之一。2008年5月12日发生在四川省西部的毁灭性地震，造成了巨大的生命损失和财产及自然破坏，这是对这一事实的严峻提醒。 第二，这是了解青藏高原碰撞后演化和向东扩张的关键区域。在一项已到期的大陆动力公司赠款下，我们在西藏东南部部署了25台宽带地震仪（08/2003-09/2004）。从这个阵列的数据的地壳结构的层析成像反演揭示了广泛的低速（和可能的机械薄弱）区。这些带可能控制该地区的变形和地震活动，但它们的性质，三维结构和相互连接，以及活动断层上的地震成因的重要性还不清楚。2006年，中国地震局在同一地区安装了300个宽带（Güralp）传感器阵列，这些数据可用于我们的项目。CEA数据的分析将在地质研究所（CEA，北京）进行。这项中美合作将涉及麻省理工学院的一名研究生和博士后以及CEA的学生和研究人员，为研究岩石圈的非均匀性和各向异性，提高我们对地震的认识提供了前所未有的机会。最近遭受毁灭性地震袭击的人口稠密地区的构造和灾害建立浅层和深层构造之间的联系以及区域过程和局部地震活动之间的联系需要对非均质、各向异性的岩石圈进行多尺度地震成像。 我们可以通过建立在数据分析（环境噪声干涉测量），方法（Eikonal和有限频率层析成像）和壮观的阵列数据（CEA）的可用性的最新进展，以满足这一挑战。 作为合乎逻辑的第一步，我们将添加（密集间隔）CEA阵列的（短周期）数据，以解决（浅）地壳非均匀性和（方位角）各向异性（瑞利波和洛夫波）。这将使人们对地壳结构与地震活动的关系有更多的新认识。为了进一步提高分辨率，我们将联合收割机干涉测量与全波反演相结合。我们采取分层的方法。我们首先考虑一个渐进的方法（Eikonal层析成像），以创建一个3D的初始模型，随后的全波（伴随）层析成像（与3D有限频率内核）。SEM合成物将用于定量模型评价和验证。 所提出的噪声干涉测量和有限频率层析成像的组合也可以应用于来自例如USAray的数据。