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Dynamic fracture by large extraterrestrial impacts as the origin of shatter cones

机译：大型外星撞击造成的动态破裂是破碎锥的起源

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摘要

A large impact by a comet or meteorite releases an enormous amount of energy, which evaporates, melts and fractures the surrounding rocks. Distinctive features of such impacts are 'shatter cones', deformed rocks characterized by hierarchical striated features. Although such features have been used for decades as unequivocal fingerprints of large-body impacts, the process by which shatter cones form has remained enigmatic. Here we show that the distinctive shatter-cone striations naturally result from nonlinear waves (front waves) that propagate along a fracture front. This explains the observed systematic increase of striation angles with the distance from the impact. Shatter-cone networks, typically spanning many scales, can be understood as hierarchical bifurcations of the fracture front, which is generated by the immense energy flux carried by the initial, impact-generated, shock waves. Our quantitative predictions based on this theory are supported by field measurements at the Kentland and Vredefort impact sites. These measurements indicate that shatter cones near to the impact site were formed by fractures propagating at nearly the Rayleigh wave speed of the host rocks, whereas the furthest shatter cones observed (about 40 km from the impact site) were formed by fronts moving more slowly. These results provide insight into impact dynamics as well as dissipative mechanisms in solids subjected to sudden, extremely intense fluxes of energy.
机译：彗星或陨石产生的巨大冲击会释放出大量能量，从而使周围的岩石蒸发，融化并破裂。这种冲击的显着特征是“破碎锥”，变形的岩石，其特征是具有分层的条纹状特征。尽管数十年来，此类特征已被用作大型物体撞击的明确指纹，但破碎锥体的形成过程一直是谜团。在这里，我们显示出独特的破碎锥条纹自然是由沿裂缝前沿传播的非线性波（前沿波）引起的。这解释了观察到的条纹角度随距冲击距离的系统增加。通常跨越许多规模的破碎圆锥网络可以理解为裂缝前沿的分层分叉，它是由初始的，冲击产生的冲击波所携带的巨大能量通量产生的。我们基于此理论的定量预测得到了肯特兰和弗雷福福特撞击点实地测量的支持。这些测量结果表明，撞击点附近的破碎锥是由几乎以宿主岩石的瑞利波速度传播的裂缝形成的，而观察到的最远的破碎锥（距离撞击点约40 km）是由锋面运动得更慢而形成的。这些结果提供了对固体的冲击动力学以及耗散机理的深刻见解，这些固体经受了突然的，极强的能量通量。

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  • 来源
    《Nature》 |2002年第6895期|p.310-313|共4页
  • 作者

    Amir Sagy; Zeev Reches; Jay Fineberg;

  • 作者单位

    Institute of Earth Sciences, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 自然科学总论;
  • 关键词

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