RESEARCH FOCUS: How Dynamic Weakening Makes Faults Stronger: The Role Of Melting In Post-Seismic Healing
RESEARCH FOCUS: How Dynamic Weakening Makes Faults Stronger: The Role Of Melting In Post-Seismic Healing
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研究重点：动态弱化如何使断层更强：融化在震后愈合中的作用
DOI：
10.1130/focus122016.1
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发表时间：
2016
期刊：
影响因子：
5.8
通讯作者：
Griffith, W. Ashley
中科院分区：
文献类型：
--
作者：
Griffith, W. Ashley
Mitchell等人以及普罗克特和Lockner认为，无论规模如何，熔融导致的断层焊接是快速强度恢复和持续强度粗糙的重要来源，这些粗糙会影响孕震区内断层的长期强度。这些新的结果对当今断层上地震滑动的力学有着重要的意义。第一，熔融可以迅速强化断层。Mitchell等人指出，GLFZ断层脉的冷却发生在5秒内，而阿尔卑斯断层的较薄断层脉在<< 1秒内发生。此外，如普罗克特和洛克纳的实验所证明的，该方法即使在非常小的熔体体积下也是有效的。Mitchell等人以及普罗克特和Lockner的综合结果表明，无论融化是广泛的（例如，GLFZ），弥漫性的（例如，GLFZ），阿尔卑斯断层），或不连续的，因为可能是更常见的情况下，熔化和随后的淬火应导致强度粗糙整个孕震区。如果熔化焊接在孕震区确实很普遍，那么滑动离域过程也可能很普遍。随着断层成熟度增加断层平滑度已经成为与来自现场观测和断层力学理论的期望一致的公认范例（Wesnousky，1988; Chester和Chester，1998; Brodsky等人，二〇一一年;纽曼和格里菲斯，2014年），然而，即使是成熟的断层在孕震深度可能是几何复杂的可能性，对地震和断层的力学有重大影响。强度不均匀性在地震的成核、传播和停止以及断层外变形中起作用。断层粗糙度形式的结构复杂性可能会增加额外的剪切阻力，从而使断层即使在局部动态弱化的情况下也可能保持宏观强度（Fang和Dunham，2013），这可能解释了为什么大多数地壳地震似乎很强。相反，在普罗克特和洛克纳的实验中，在潮湿条件下缺乏再强化，这似乎表明，虽然热加压，像熔化一样，是一种有效的动态弱化机制，但就如何影响长期断层强度而言，它可能与熔化有根本的不同。如果正确的话，这就提出了无数其他热驱动动态弱化机制的作用问题（Di Toro等人，2011）在震后强度恢复和随后的地震活动中（McLaskey等人，2012年）。可以说，地震后断层愈合在地震周期中的作用值得像当前流行的“热门”话题动态摩擦弱化一样关注。
Mitchell et al. and Proctor and Lockner is that regardless of scale, fault welding resulting from melting represents a significant source of rapid strength recovery and persistent strength asperities that can influence the long-term strength of faults within the seismogenic zone. These new results have some critical implications for the mechanics of seismic slip on faults in the present day. First, melting can strengthen faults rapidly. Mitchell et al. note that cooling of GLFZ fault veins occurred as quickly as 5 s, and the thinner fault veins of the Alpine fault in<< 1 s. Furthermore, as demonstrated by the experiments of Proctor and Lockner, this process is effective even with very small melt volumes. The combined results of Mitchell et al. and Proctor and Lockner suggest that whether melting is widespread (eg, the GLFZ), diffuse (eg. the Alpine fault), or discontinuous, as may be the more common case, melting and subsequent quenching should result in strength asperities throughout the seismogenic zone. And if melt welding is indeed widespread in the seismogenic zone, so too may be the process of slip delocalization. Increasing fault smoothness with fault maturity has become the accepted paradigm consistent with expectations from field observations and fault mechanics theory (Wesnousky, 1988; Chester and Chester, 1998; Brodsky et al., 2011; Newman and Griffith, 2014), yet the possibility that even mature faults may be geometrically complex at seismogenic depths has major implications for the mechanics of earthquakes and faulting. Strength heterogeneity plays a role in earthquake nucleation, propagation, and cessation, as well as off-fault deformation. Structural complexity in the form of fault roughness may add additional shear resistance to slip such that faults may remain macroscopically strong even with local, dynamic weakening (Fang and Dunham, 2013), perhaps explaining why most crustal earthquakes appear to be strong. In contrast, the lack of re-strengthening under wet conditions in Proctor and Lockner’s experiments seems to suggest that whereas thermal pressurization, like melting, is an effective dynamic weakening mechanism, it may differ fundamentally from melting in terms of how it affects longterm fault strength. If correct, this raises the question of the role of the myriad other thermally driven dynamic weakening mechanisms (Di Toro et al., 2011) in post-seismic strength recovery and subsequent seismicity (McLaskey et al., 2012). It could be argued that the role of post-seismic fault healing over the seismic cycle deserves as much focus as the prevailing “hot” topic of dynamic frictional weakening.
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