The earthquake cycle in the dry lower continental crust: insights from two deeply exhumed terranes (Musgrave Ranges, Australia and Lofoten, Norway).
The earthquake cycle in the dry lower continental crust: insights from two deeply exhumed terranes (Musgrave Ranges, Australia and Lofoten, Norway).
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DOI：
10.1098/rsta.2019.0416
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发表时间：
2021-03-22
期刊：
影响因子：
--
通讯作者：
Pennacchioni G
中科院分区：
文献类型：
--
作者：
Menegon L;Campbell L;Mancktelow N;Camacho A;Wex S;Papa S;Toffol G;Pennacchioni G
本文讨论了在马斯格雷夫山脉（澳大利亚中部）和努斯峡湾（挪威罗弗敦）暴露的出土岩石的野外地质调查结果，保存了震源深度约为25-40公里的下大陆地壳地震的证据。这些研究已经确定，干燥的下陆壳变形的特点是粘性蠕变（糜棱岩化）和脆性地震滑动之间的周期性相互作用，与假玄武玻璃（在硅酸盐岩石中沿着断层地震滑动期间产生的凝固熔体）的形成有关。地震滑动触发流变弱化和向粘性蠕变的转变，这可能在地震后立即沿沿着断层变形期间已经活跃，最初的特征是摩擦熔融和围岩破坏。地震滑动和粘性蠕变之间的周期性相互作用意味着应力和应变率的瞬态振荡，这是保存在剪切带的微观结构。在这两个地方，pseudotrachylytes的空间分布是一致的本地（深）源的瞬态高应力所需的下地壳地震。这种深源是局部应力放大的结果，在与韧性剪切带接触产生的干燥和强大的材料，产生多代假玄武玻璃在地质时间。这意味着，无论是短期和长期的流变演化的干燥下地壳典型的大陆内部的地震周期变形控制。这篇文章是讨论会议题“利用地质记录了解地震”的一部分。
This paper discusses the results of field-based geological investigations of exhumed rocks exposed in the Musgrave Ranges (Central Australia) and in Nusfjord (Lofoten, Norway) that preserve evidence for lower continental crustal earthquakes with focal depths of approximately 25–40 km. These studies have established that deformation of the dry lower continental crust is characterized by a cyclic interplay between viscous creep (mylonitization) and brittle, seismic slip associated with the formation of pseudotachylytes (a solidified melt produced during seismic slip along a fault in silicate rocks). Seismic slip triggers rheological weakening and a transition to viscous creep, which may be already active during the immediate post-seismic deformation along faults initially characterized by frictional melting and wall-rock damage. The cyclical interplay between seismic slip and viscous creep implies transient oscillations in stress and strain rate, which are preserved in the shear zone microstructure. In both localities, the spatial distribution of pseudotachylytes is consistent with a local (deep) source for the transient high stresses required to generate earthquakes in the lower crust. This deep source is the result of localized stress amplification in dry and strong materials generated at the contacts with ductile shear zones, producing multiple generations of pseudotachylyte over geological time. This implies that both the short- and the long-term rheological evolution of the dry lower crust typical of continental interiors is controlled by earthquake cycle deformation. This article is part of a discussion meeting issue ‘Understanding earthquakes using the geological record’.
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影响因子：
13.6
作者：
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