An assessment of low-temperature, ductile lithospheric deformation using existing broadband seismic data from around South Island, New Zealand

使用新西兰南岛周围现有的宽带地震数据评估低温、延性岩石圈变形

• 批准号: 2316757
• 负责人: Hannah Mark
• 金额: $ 8.44万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2316757&HistoricalAwards=false
• 关键词: assessment; low; temperature; ductile; lithospheric

Plate tectonics involves rigid lithospheric plates moving over an asthenosphere which can flow on geologic time scales. However, there is new evidence that the ‘rigid’ lithosphere might be able to deform. This project will study if ductile behavior – when material flows instead of breaking – is present at the Alpine Fault in South Island, New Zealand. Results will have implications for global tectonic processes. Broader impacts include support for an early career scientist and dissemination of software related to the project.The main goal of the proposed research is to assess whether shear stress leads to low-temperature ductile deformation in the lithosphere. Seismic anisotropy, a proxy for viscous strain, will be used to test whether ductile deformation is occurring at low temperatures in the lithospheric mantle around the Alpine Fault in South Island, New Zealand. While previous studies have shown that strain associated with relative motion across the Alpine Fault is accommodated in a zone up to 200 km wide, prior anisotropy measurements from shear wave splitting and earthquake Pn have not provided sufficient spatial resolution to determine whether deformation is occurring in the lithosphere or the asthenosphere away from the plate boundary. An existing ocean bottom seismic dataset will be used to calculate receiver functions, applying recently developed techniques for removing sediment and water column reverberations, and harmonic decomposition will be used to measure azimuthal anisotropy in the lithospheric mantle on both sides of South Island. This will resolve lateral and vertical variations in seismic anisotropy around the Alpine Fault and determine where ductile deformation is occurring in the lithosphere-asthenosphere system.This project is supported by the Marine Geology and Geophysics program in the Division of Ocean Sciences and the Geophysics program in the Division of Earth Sciences.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.

板块构造涉及刚性岩石圈板，在软圈上移动，该板可以在地质时间尺度上流动。但是，有新的证据表明“刚性”岩石圈可能会变形。该项目将研究延展性行为（当物质流动而不是破裂时）存在于新西兰南岛的高山断层。结果将对全球构造过程产生影响。更广泛的影响包括对早期职业科学家的支持和与该项目相关的软件的传播。拟议的研究的主要目标是评估剪切应力是否导致岩石圈中的低温延性变形。地震各向异性是粘性菌株的代理，将用于测试在新西兰南岛高山断层周围岩石圈地幔的低温下是否发生延展性变形。虽然先前的研究表明，与跨高山断层相对运动相关的应变可容纳在宽度200公里的区域中，但剪切波分裂和地震PN的先前各向异性测量尚未提供足够的空间分辨率来确定在岩石圈还是远处源于远离板圈边界中是否发生变形。现有的海洋底部地震数据集将用于计算接收器功能，应用最近开发的技术来消除沉积物和水柱回响，并将使用谐波分解来测量南岛两侧岩石圈地幔的方位角各向异性。这将解决高山断层周围的地震各向异性的横向和垂直变化，并确定在岩石圈 - 亚特赛层系统中发生的延性畸形。通过使用基金会的智力优点和更广泛影响的评论标准进行评估。