Collaborative Research: Experimental analysis of strain transients in a heterogeneous semi-brittle system: Implications for tectonics

构造运动引起破坏性地震和断裂带上神秘的缓慢滑动事件。描述断裂或粗糙断层表面滑动的脆性行为和摩擦定律并不能解释这样一个事实，即断层带可以同时以脆性方式断裂，并以韧性方式流动，正如地质记录中所观察到的那样。该项目将实验室实验和理论分析结合起来，研究半脆性材料对变形局部化和滑移积累机制的影响，这可能为地震力学提供重要见解。该项目提出，从地震到稳定蠕变的变形速度的广泛变化可以用半脆性材料的脆性断裂和韧性流动的相互作用来解释。这种行为将通过使用Carbopol的物理实验来探索，Carbopol同时表现出脆性和延性变形。实验将测试半脆性材料中拉伸和剪切断裂的相互作用是否会导致应变瞬变，或者，如果，相反，再次发生的应变瞬变是由沿剪切断裂的强度控制的，这样断裂的形成似乎只与滑移同时发生。这些结果将被纳入一个分析模型，该模型允许将结果外推到与地球应变瞬变相关的时间尺度。本文提出的工作将从根本上促进对半脆性变形及其对应变瞬态的影响的理解。

Tectonic motions give rise to destructive earthquakes and to enigmatic slower slip events on fault zones. Brittle behavior and friction laws that describe slip over fractured or rough fault surfaces do not account for the fact that fault zones can simultaneously break in a brittle manner and flow in a ductile way as has been observed in the geologic record. This project combines laboratory experiments and theoretical analysis on the effect a semi-brittle material can have on the mechanisms of deformation localization and slip accumulation, which may provide critical insights on the mechanics of earthquakes.This project proposes that the wide variation in deformation speeds from earthquake to steady creep can be explained by the interaction of brittle fracturing and ductile flow in a semi-brittle material. This behavior will be explored with physical experiments using Carbopol, which exhibits both brittle and ductile deformation simultaneously. The experiments will test whether the interaction of tensional and shear fractures in a semi-brittle material leads to strain transients, or if, alternatively, the re-occurring strain transients are controlled by the strength along the shear fracture such that the formation of the fractures only appears to be concurrent with the slip. The results will be incorporated into an analytical model, which allows extrapolating the results to time scales relevant to strain transients in Earth. The work proposed here will fundamentally advance the understanding of semi-brittle deformation and its impact on strain transients.