Scaling of fault damage zones with displacement and the implications for fault growth processes
Scaling of fault damage zones with displacement and the implications for fault growth processes
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DOI：
10.1029/2010jb007788
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发表时间：
2011-05
影响因子：
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通讯作者：
D. Faulkner;T. Mitchell;E. Jensen;J. Cembrano
中科院分区：
文献类型：
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作者：
D. Faulkner;T. Mitchell;E. Jensen;J. Cembrano
[1]了解断裂带周围破坏的空间范围对于了解地壳流体流动以及了解断裂带随着滑动而发展的物理过程和机制很重要。关于断层破坏带与断层位移的比例关系的现有数据很少，而且在现有的数据中，通过比较穿过不同岩性、在不同地壳深度或不同构造体制(例如，正常运动与走滑运动)形成的断层，难以得出比例关系。我们描述了智利北部阿塔卡马断裂带内小位移断裂带的微破裂破坏带宽度的新数据，该断裂带形成于∼6公里深的闪长岩原岩中。微裂缝损伤区表现为断层周围的蚀变晕，微裂缝的密度远大于未变形原岩的背景水平。数据表明，损伤带宽度随着断层位移的增加而增加，这种关系似乎存在零截距，这意味着在零位移下，不存在微裂缝损伤带。这一点得到了断层尖端的现场观察的支持，这些观察显示断层损伤区逐渐变小。这些数据，结合文献中的数据，表明这种相同的关系可能适用于更大的位移断层。断裂损伤也存在明显的不对称性。讨论了观测标度发展的几个过程。被广泛接受的过程带理论预测，断层破坏带宽度随着断层长度的增加而增加，因此在位移最小的传播断层尖端总是最大的。这一预测与当前数据集中看到的相反，这表明其他过程，例如由于几何不规则或同震破坏形成而导致位移增加的损伤区增长，可能更好地解释即使是低位移断层周围的损害空间范围。
[1] Knowledge of the spatial extent of damage surrounding fault zones is important for understanding crustal fluid flow and also for understanding the physical processes and mechanics by which fault zones develop with slip. There are few data available on the scaling of the fault damage zone with fault displacement, and of those that exist, deriving scaling relationships is hampered by comparing faults that run through different lithologies, have formed at different crustal depths or tectonic regimes (e.g., normal versus strike‐slip movement). We describe new data on the microfracture damage zone width from small displacement fault zones within the Atacama fault zone in northern Chile that formed at ∼6 km depth within a dioritic protolith. The microfracture damage zone is shown by an alteration halo surrounding the faults in which the density of the microfractures is much greater than background levels in the undeformed protolith. The data show that damage zone width increases with fault displacement and there appears to be a zero intercept to this relationship, meaning that at zero displacement, there is no microfracture damage zone. This is supported by field observations at fault tips that show a tapering out of fault damage zones. These data, combined with data from the literature, indicate that this same relationship might hold for much larger displacement faults. There is also a distinct asymmetry to the fracture damage. Several processes for the development of the observed scaling are discussed. The widely accepted theory of a process zone predicts that fault damage zone width increases with fault length and thus should always be largest at a propagating fault tip where displacement is lowest. This prediction is opposite to that seen in the current data set, leading to suggestion that other processes, such as damage zone growth with increasing displacement due to geometric irregularities or coseismic damage formation might better explain the spatial extent of damage surrounding even low‐displacement faults.