Deformation, Fluid Generation, and Seismogenesis in a Transitional Subduction Environment, the Marlborough Region, New Zealand, Revealed with a Magnetotelluric Resistivity Transect

大地电磁电阻率断面揭示了新西兰马尔伯勒地区过渡俯冲环境中的变形、流体生成和地震成因

• 批准号: 0440050
• 负责人: Philip Wannamaker
• 金额: --
• 依托单位: University of Utah
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-01 至 2010-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0440050&HistoricalAwards=false
• 关键词: Deformation; Fluid; Generation; Seismogenesis; Transitional

Intellectual Merit of Research. - The Marlborough strike slip fault system of New Zealand clearly exemplifies the transition in plate convergence from near decoupling between upper and lower plates in true subduction (northern North Island), to essentially complete coupling between the plates with near-continuous thickening of the crust and upper mantle and no subduction (central South Island). In Marlborough, four major dextral fault zones at a low angle to the present Australian-Pacific plate convergence direction accommodate most of the component of motion parallel to the plate boundary. A magnetotelluric (MT) geophysical transect of the region is to be carried out to clarify controls on internal physical state of strike slip fault zones, and fill a gap in understanding of transpressional orogens between uncoupled and fully coupled situations. Basic questions to be addressed include: 1) How much are seismogenic faults fluidized, which may influence stress buildup?, 2) Is the fluid state of fault zones a function of cumulative displacement or degree of activity?, 3) Do major fault zones acquire their fluids locally, or from the lower crust?, 4) What are the physical conditions in the crust as major strike slip faults initiate?, 5) What enables coupling between subducting and overriding plates to develop?, 6) Is the subduction interface sharp, or is there a broad zone of diffuse deformation?, 7) If fluids help control rheology near the subduction interface, what is their origin?, and 8) Do slab dehydration reactions contribute to seismicity of the downgoing slab?Broader Impacts of the Research. - The proposal is a fully cooperative effort between the University of Utah of the United States and the Institute of Geological and Nuclear Sciences (IGNS) of New Zealand in research into an important solid earth problem. Support for a female graduate student is made available for education into state of the art geophysical instrumentation, parameters of field survey design, practical logistical matters in overseas settings, modern methods of inversion, and the relationship between electrical resistivity and physico-chemical state in the Earth. The utility of off-the-shelf commercial geophysical instrumentation for specialized solid earth studies is tested and the project raises the profile of electrical methods, an underutilized field, in solid earth science. Additional societal benefits include broader understanding of the controls on fault strength and ability to build up damaging stresses.

研究的智力价值。- 新西兰的马尔伯勒走滑断层系统清楚地证明了板块会聚从真正俯冲时上下板块之间的接近分离（北岛北方）到板块之间基本上完全耦合（地壳和上地幔接近连续增厚而没有俯冲）（南岛中部）的转变。在马尔伯勒，四个主要的右旋断裂带与现在的澳大利亚-太平洋板块会聚方向成低角度，容纳了平行于板块边界的运动分量的大部分。一个大地电磁（MT）地球物理断面的区域进行澄清内部物理状态的走滑断裂带的控制，并填补了认识的差距之间的扭压造山带的非耦合和完全耦合的情况。要解决的基本问题包括：1）发震断层的流体化程度有多大，这可能影响应力的积累？2)断层带的流体状态是累积位移的函数还是活动程度的函数？3)主要的断层带是局部地还是从下地壳获得流体？4)当主要的走滑断层开始时，地壳中的物理条件是什么？5)是什么使俯冲板块和俯冲板块之间的耦合得以发展？6)俯冲界面是尖锐的，还是有一个广泛的扩散变形区？7)如果流体有助于控制俯冲界面附近的流变学，它们的起源是什么？板块脱水反应对下行板块的地震活动性有贡献吗？研究的更广泛影响。- 该建议是美国犹他州大学和新西兰地质和核科学研究所在研究一个重要的固体地球问题方面的充分合作努力。向一名女研究生提供支助，使其学习最先进的地球物理仪器、实地勘测设计参数、海外环境中的实际后勤事项、现代反演方法以及电阻率与地球物理化学状态之间的关系。测试了用于专门固体地球研究的现成商业地球物理仪器的效用，该项目提高了固体地球科学中未充分利用的电学方法的形象。 其他的社会效益包括更广泛地理解对断层强度的控制和建立破坏性应力的能力。