Fault Surface Bumps: Prevalence, Causes and Consequences

断层表面凸起：普遍性、原因和后果

• 批准号: 0711575
• 负责人: Emily Brodsky
• 金额: $ 20万
• 依托单位: University of California-Santa Cruz
• 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: 2007-07-01 至 2010-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0711575&HistoricalAwards=false
• 关键词: Fault; Surface; Bumps; Prevalence; Causes

Fault surface geometry affects all aspects of earthquake mechanics, yet until recently quantitative field data of fault shapes at the scale of earthquake slip has been scarce. We have begun to attack the problem using a combination of ground-based laser distance measurements and laboratory analyses. This initial work has already increased the available data on fault surfaces by several orders of magnitude and produced new geological observations. The data quantitatively shows that large-slip faults are smoother than small-slip ones. More strikingly, all pristine, large-scale exposures of mature faults that have been measured thus far have distinct quasi-elliptical bumps at the 10's of meter scale. These 3D bumps, known in fault mechanics as asperities, are a new field observation and the focus of the present study. Specifically, the investigators are now determining how commonly such bumps occur on a variety of fault, measuring the relationship between the bump occurrence and surround rock types, constraining the origin of bumps by measuring the total amount abraded rock powder in the bump's vicinity, mapping the occurrence of rock damage near bumps, numerically modeling the bump's stress field on the surround rocks and using seismic data to determine if the earthquakes on mature, smooth faults are different than those on immature, rough ones.

断层面的几何形状影响着地震力学的各个方面，然而直到最近，地震滑动尺度上的断层形状的定量现场数据还很缺乏。我们已经开始使用地面激光距离测量和实验室分析相结合的方法来解决这个问题。这一初步工作已经将断层表面的可用数据增加了几个数量级，并产生了新的地质观测结果。 数据定量表明，大滑动断层比小滑动断层更光滑。更令人吃惊的是，迄今为止所测量的成熟断层的所有原始的大规模暴露都具有明显的准椭圆形隆起，其尺度为10米。这些三维隆起，在断层力学中称为粗糙体，是一个新的现场观察和本研究的重点。具体来说，调查人员现在正在确定这种隆起在各种断层上发生的频率，测量隆起发生与围岩类型之间的关系，通过测量隆起附近磨损的岩石粉末总量来限制隆起的起源，绘制隆起附近岩石损伤的发生，数值模拟凸起对周围岩石的应力场，并使用地震数据来确定成熟的光滑断层上的地震是否与不成熟的粗糙断层上的地震不同。