Nielsen S, Spagnuolo E, Violay M, Smith S, Di Toro G, Bistacchi A
Istituto Nazionale di Geofisica e Vucanologia, Rome, Italy ; Durham University, Earth Sciences, Durham, UK.
Istituto Nazionale di Geofisica e Vucanologia, Rome, Italy.
J Seismol. 2016;20(4):1187-1205. doi: 10.1007/s10950-016-9560-1. Epub 2016 Mar 31.
Recent estimates of fracture energy in earthquakes show a power-law dependence with slip which can be summarized as ∝ where is a positive real slightly larger than one. For cracks with sliding friction, fracture energy can be equated to : the post-failure integral of the dynamic weakening curve. If the dominant dissipative process in earthquakes is friction, and should be comparable and show a similar scaling with slip. We test this hypothesis by analyzing experiments performed on various cohesive and non-cohesive rock types, under wet and dry conditions, with imposed deformation typical of seismic slip (normal stress of tens of MPa, target slip velocity > 1 m/s and fast accelerations ≈ 6.5 m/s). The resulting fracture energy is similar to the seismological estimates, with and being comparable over most of the slip range. However, appears to saturate after several meters of slip, while in most of the reported earthquake sequences, appears to increase further and surpasses at large magnitudes. We analyze several possible causes of such discrepancy, in particular, additional off-fault damage in large natural earthquakes.
近期对地震断裂能的估计表明，其与滑动存在幂律依赖关系，可总结为∝ ，其中 是一个略大于1的正实数。对于存在滑动摩擦的裂缝，断裂能可等同于 ：动态弱化曲线的破坏后积分。如果地震中主要的耗散过程是摩擦，那么 和 应该具有可比性，并且随滑动表现出相似的标度关系。我们通过分析在各种粘性和非粘性岩石类型上进行的实验来检验这一假设，实验在潮湿和干燥条件下进行，施加了典型地震滑动的变形（数十兆帕的正应力、目标滑动速度>1米/秒以及约6.5米/秒²的快速加速度）。由此得到的断裂能 与地震学估计值相似，在大部分滑动范围内 和 具有可比性。然而， 在滑动数米后似乎趋于饱和，而在大多数已报道的地震序列中， 在震级较大时似乎会进一步增加并超过 。我们分析了造成这种差异的几种可能原因，特别是大型天然地震中额外的断层外损伤。
