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.

该奖项由 2009 年美国复苏和再投资法案（公法 111-5）资助。我们研究的主要目的是利用新的方法提高我们对西藏东南部地壳和岩石圈地幔的结构和变形的理解。从地质角度来看，四川盆地和东喜马拉雅地震带之间的地区具有重要意义，其一是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人员伤亡以及财产和自然的破坏，这是一个严峻的事实。这是了解青藏高原碰撞后演化和向东扩张的关键区域。根据大陆动力学资助计划，我们在西藏东南部部署了 25 个宽带地震仪。 (08/2003-09/2004)。该阵列数据的地壳结构层析反演揭示了广泛的低速区域（可能是机械弱区域），这些区域可能控制该地区的变形和地震活动，但它们的性质3。 -D 结构和连通性以及对活动断层地震发生的重要性尚不清楚。2006 年，中国地震局在同一地区安装了 300 个宽带阵列。 （Güralp）传感器，这些数据可供我们用于我们的项目。CEA 数据的分析将在地质研究所（CEA，北京）进行，该项目将涉及一名研究生。麻省理工学院的博士后以及 CEA 的学生和研究人员，提供了前所未有的机会来研究岩石圈的非均质性和各向异性，并提高我们对人口稠密地区的地震构造和危险的理解。最近遭受了一场毁灭性的地震，建立浅层和深层结构之间的联系以及区域过程和局部地震活动之间的关系需要对非均质、各向异性岩石圈进行多尺度地震成像，我们可以通过利用数据分析（环境噪声）的最新进展来应对这一挑战。干涉测量）、方法（Eikonal 和有限频率断层扫描）以及壮观阵列数据 (CEA) 的可用性作为合乎逻辑的第一步，我们将添加来自（密集）的（短周期）数据。间隔）CEA 阵列来解决（浅层）地壳异质性和（方位角）各向异性（瑞利波和洛夫波），这将为与地震活动相关的地壳结构提供更多新的见解。为了进一步提高分辨率，我们将干涉测量与全波相结合。我们采用分层方法（Eikonal 断层扫描）来为后续全波（伴随）断层扫描创建 3D 起始模型。 SEM 合成材料将用于定量模型评估和验证，所提议的噪声干涉测量和有限频率断层扫描的组合也可以应用于来自 USArray 等的数据。