SGER: Integrated Petrophysical and Seismological Investigation of Crustal Fabric and Seismic Anisotropy of a Major Crustal Suture Zone, the Cheyenne Belt, Wyoming

SGER：怀俄明州夏安带地壳结构和主要地壳缝合带地震各向异性的综合岩石物理和地震学调查

• 批准号: 0750035
• 负责人: Kevin Mahan
• 金额: --
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-15 至 2010-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0750035&HistoricalAwards=false
• 关键词: SGER; Integrated; Petrophysical; Seismological; Investigation

Detection of seismic anisotropy in deep continental crust is a powerful new tool for mapping 3-dimensional crustal fabric in a variety of tectonic settings and in both modern and ancient orogens. Recent results, using improved receiver function analysis methods, reveal detailed information about km-scale subsurface fabric geometry that promises new insight into the active and long-term dynamic history of orogenic systems. Such analysis will also undoubtedly be an important component in future EarthScope projects aimed at understanding North American lithospheric structure and evolution. However, most crustal anisotropic receiver function studies to date lack geological and laboratory ground truth. Consequently, the gap between our ability to image detailed crustal structure and to accurately interpret these observations is widening due to continued uncertainty about the details of how crustal seismic anisotropy is developed, preserved, and destroyed. While conventional knowledge is that deep crustal anisotropy is fundamentally controlled by deformation-induced crystallographically preferred orientation (CPO) of highly anisotropic mica, there are still many unanswered questions about other potentially important factors such as (i) the role of other silicate minerals and the effects of their constructive and/or destructive interference; (ii) the contribution of fabric components other than the commonly assumed single foliation, such as lineation and composite shear fabrics; (iii) crustal metamorphic processes and deformation mechanisms; and (iv) alignment and length scale of anisotropic fabric compared to seismic wavelengths. The researchers will begin addressing these questions through an integrated seismic and petrophysical pilot study of a major crustal-scale suture zone in North America, the Proterozoic Cheyenne Belt in southern Wyoming. Several important advantages make this belt an ideal candidate for the proposed study: (1) it is a deeply exhumed (15 km paleodepth), crustal-scale zone of highly strained tectonite that is likely to have developed significant fabric-induced seismic anisotropy; (2) abundant published geological and geophysical results from the area provide a base; and (3) an excellent existing data set of broadband seismic waveforms from dense networks spanning the region is available and has yet to be analyzed for crustal anisotropy.The project will also involve evening presentations for Front Range science teachers during the academic year, followed by a one-day K-12 teacher workshop on earthquakes, faults, and the geology related to the project. The presentations and workshops, to be developed with the CIRES outreach group, will cover (1) geologic observations of faults and (2) seismology and earthquakes. Other broader impacts include research involvement of undergraduates, support of two junior career scientists, and the project's cross-disciplinary nature.

在深色大陆地壳中检测地震各向异性是一种强大的新工具，用于在各种构造环境以及现代和古老的Ogens中绘制三维地壳织物。最近的结果，使用改进的接收器功能分析方法揭示了有关KM规模地下织物几何形状的详细信息，该信息有望对造山学系统的主动和长期动态历史进行新的见解。这种分析无疑也将成为旨在了解北美岩石圈结构和进化的未来地球景观项目中的重要组成部分。但是，迄今为止，大多数地壳各向异性接收器功能研究都缺乏地质和实验室基础真理。因此，由于持续不确定性，关于地壳地震各向异性如何开发，保存和破坏的细节，我们的图像详细地壳结构的能力与准确解释这些观察结果之间的差距正在扩大。虽然传统的知识是深层地壳各向异性在根本上受到了高度各向异性云母的变形诱导的晶体学首选取向（CPO）的控制，但仍然存在许多有关其他潜在重要因素的未解决的问题，例如（i）其他硅酸盐矿物质和其他硅酸盐和矿物质的作用其建设性和/或破坏性干扰的影响； （ii）除了通常假定的单叶（例如衬里和复合剪切织物）以外的织物成分的贡献； （iii）地壳变质过程和变形机制； （iv）与地震波长相比，（iv）各向异性织物的比对和长度尺度。研究人员将通过对北美一个主要的地壳规模的缝合区进行综合的地震和岩石物理试点研究来解决这些问题，北美是怀俄明州南部的protereroxoic cheyenne腰带。几个重要的优势使该皮带成为拟议研究的理想候选者：（1）它是一个深度挖掘的（15 km古植物），地壳尺度高度紧张的构造岩石区，可能会形成明显的织物诱导的地震性各向异性； （2）该地区的大量已发表的地质和地球物理结果提供了基础； （3）从该地区的密集网络的宽带地震波形的现有数据集可用，并且尚未分析地壳各向异性。该项目还将在学年中为前排科学教师提供晚间演讲，然后涉及。与该项目有关的一日K-12教师讲习班和地质。演讲和讲习班将与CIRES宣传集团一起开发，将涵盖（1）对断层和（2）地震学和地震的地质观察。其他更广泛的影响包括本科生的研究参与，两名初级职业科学家的支持以及该项目的跨学科性质。