Collaborative Research: Structure and depth extent of lithospheric shear zones surrounding continental transform faults

合作研究：大陆转换断层周围岩石圈剪切带的结构和深度范围

• 批准号: 1927216
• 负责人: Thorsten Becker
• 金额: $ 30.08万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-10-01 至 2024-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1927216&HistoricalAwards=false
• 关键词: Collaborative; Research; Structure; depth; extent

At continental transform faults such as the San Andreas, one tectonic plate slides horizontally relative to its neighbor. Because such faults lie on land and often in populated areas, the resulting earthquakes dramatically impact local populations. It remains debated how plates deform beneath the shallow (~10 km), top layer where earthquakes are generated. At larger depths, underlying rocks transition from brittle to ductile deformation. But whether the shear zone underneath the fault remains narrow for tens of km, or whether deformation widens right away is not clear. These different scenarios affect how faults are loaded, and have significant implications for seismic hazard assessment. Here, the team uses existing seismic records to investigate six major continental transform faults. Deformed rocks often exhibit crystal preferred orientations, fabrics, that can be detected with seismic waves. This is because rock fabrics affect the wave velocity which then depends on the propagation direction. By analyzing the anisotropy of seismic waves passing underneath the fault zones, the researchers probe the geometry and extent of rocks deformation. They also use geodynamic modeling constrained by geological observations; for given fault geometries and deformation properties, they predict seismic anisotropy features underneath the faults. By comparing observations and predictions, the team unravels the deformation behavior of continental transform faults. The project fosters an international collaboration with Australia and Switzerland. It provides support and training to a female graduate student, and outreach toward undergraduates and K12 students - notably from group underrepresented in Sciences - and the public. The team uses data from existing deployments crossing six continental transform faults (San Andreas, North Anatolian, Denali, New Zealand Alpine, Altyn Tagh/Kunlun, and Dead Sea). It conducts full-waveform 2-D and 3-D modeling of teleseismic shear wave splitting, as well as anisotropic receiver function analysis. The goal is to image the shear zone and broader deformation field surrounding each transform fault. The selected faults represent transforms of different ages and maturity. Existing splitting observations show systematic contrasts between faults. Combining high-resolution shear zone imaging and geodynamic modeling, the researchers investigate the degree of strain localization in the lithosphere and the shear zone geometry. They also study the possible roles of mechanical anisotropy and inherited fabrics. This project is a critical step toward establishing a model for continental lithospheric transforms and better assessing the corresponding earthquake hazards.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在大陆变换断层（例如圣安德烈亚斯），一个构造板相对于邻居水平滑动。由于这些断层在陆地上，通常在人口稠密的地区，因此地震极大地影响了当地人口。它仍然在争论板如何在浅层（约10 km）下方变形，即产生地震的顶层。在较大的深度，岩石从脆性变形到延性变形。但是，是否在数十km的断层下方的剪切区保持狭窄，或者变形是否会立即扩大。这些不同的情况会影响断层的加载方式，并对地震危害评估产生重大影响。在这里，团队使用现有的地震记录来调查六个主要的大陆转换故障。变形的岩石通常表现出晶体优选的方向，织物，可以用地震波检测到。这是因为岩石织物会影响波速，然后取决于传播方向。通过分析在断层区域下方的地震波的各向异性，研究人员探测了岩石变形的几何形状和程度。他们还使用受地质观察约束的地球动力学建模；对于给定的断层几何和变形特性，它们预测断层下方的地震各向异性特征。通过比较观察和预测，团队揭开了大陆变换故障的变形行为。该项目促进了与澳大利亚和瑞士的国际合作。它为女性研究生提供了支持和培训，并向大学生和K12学生提供宣传 - 尤其是来自科学领域不足的小组和公众。 该团队使用跨越六个大陆转型故障的现有部署的数据（圣安德烈亚斯，北安纳托利亚人，丹纳利，新西兰阿尔pine，Altyn Tagh/kunlun和Deade Sea）。它对远距离抗剪切波分裂以及各向异性接收器函数分析进行全波2-D和3-D模型。目标是对每个变换故障的剪切带和更宽的变形场进行图像。选定的故障代表不同年龄和成熟度的变换。现有的分裂观测显示出故障之间的系统对比度。研究人员结合了高分辨率剪切区成像和地球动力学建模，研究了岩石圈和剪切区几何形状中应变定位的程度。他们还研究了机械各向异性和遗传织物的可能作用。该项目是建立大陆岩石圈转换模型并更好地评估相应地震危害的重要一步。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子和更广泛影响的评估评估标准来通过评估来支持的。

项目成果

Imaging the Tectonic Grain of the Northern Cordillera Orogen Using Transportable Array Receiver Functions

• DOI: 10.1785/0220200182
• 发表时间: 2020-11
• 期刊: Seismological Research Letters
• 影响因子: 3.3
• 作者: V. Schulte‐Pelkum;J. Caine;James V. Jones;T. Becker

On the Role of Rheological Memory for Convection‐Driven Plate Reorganizations

流变记忆对对流驱动板重组的作用

• DOI: 10.1029/2022gl099574
• 发表时间: 2022
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Fuchs, L.;Becker, T. W.
• 通讯作者: Becker, T. W.

Tectonic Inheritance During Plate Boundary Evolution in Southern California Constrained From Seismic Anisotropy

• DOI: 10.1029/2021gc010099
• 发表时间: 2021-08
• 期刊: Geochemistry
• 影响因子: 3.7
• 作者: V. Schulte‐Pelkum;T. Becker;W. Behr;M. Miller

Asthenospheric low-velocity zone consistent with globally prevalent partial melting

• DOI: 10.1038/s41561-022-01116-9
• 发表时间: 2023-02-06
• 期刊: NATURE GEOSCIENCE
• 影响因子: 18.3
• 作者: Hua, Junlin;Fischer, Karen M.;Hirth, Greg
• 通讯作者: Hirth, Greg

Multiscale, radially anisotropic shear wave imaging of the mantle underneath the contiguous United States through joint inversion of USArray and global data sets

通过 USArray 和全球数据集的联合反演，对美国本土下方的地幔进行多尺度、径向各向异性剪切波成像

• DOI: 10.1093/gji/ggab185
• 发表时间: 2021
• 期刊: Geophysical Journal International
• 影响因子: 2.8
• 作者: Porritt, Robert W;Becker, Thorsten W;Boschi, Lapo;Auer, Ludwig
• 通讯作者: Auer, Ludwig