Di Toro Giulio, Goldsby David L, Tullis Terry E
Dipartimento di Geologia, Paleontologia e Geofisica, Universita' di Padova, Padova, 35137, Italy.
Nature. 2004 Jan 29;427(6973):436-9. doi: 10.1038/nature02249.
An important unsolved problem in earthquake mechanics is to determine the resistance to slip on faults in the Earth's crust during earthquakes. Knowledge of coseismic slip resistance is critical for understanding the magnitude of shear-stress reduction and hence the near-fault acceleration that can occur during earthquakes, which affects the amount of damage that earthquakes are capable of causing. In particular, a long-unresolved problem is the apparently low strength of major faults, which may be caused by low coseismic frictional resistance. The frictional properties of rocks at slip velocities up to 3 mm s(-1) and for slip displacements characteristic of large earthquakes have been recently simulated under laboratory conditions. Here we report data on quartz rocks that indicate an extraordinary progressive decrease in frictional resistance with increasing slip velocity above 1 mm s(-1). This reduction extrapolates to zero friction at seismic slip rates of approximately 1 m s(-1), and appears to be due to the formation of a thin layer of silica gel on the fault surface: it may explain the low strength of major faults during earthquakes.
地震力学中一个重要的未解决问题是确定地震期间地壳断层上的抗滑力。同震抗滑力的知识对于理解剪应力降低的幅度以及因此对于地震期间可能发生的近断层加速度至关重要，而这会影响地震能够造成的破坏程度。特别是，一个长期未解决的问题是主要断层的强度明显较低，这可能是由同震摩擦阻力低导致的。最近在实验室条件下模拟了岩石在高达3毫米/秒的滑动速度以及大地震特征性滑动位移情况下的摩擦特性。在此我们报告关于石英岩的数据，这些数据表明，在滑动速度高于1毫米/秒时，摩擦阻力随着滑动速度的增加而异常地逐渐降低。这种降低在地震滑动速率约为1米/秒时外推至零摩擦，并且似乎是由于在断层面上形成了一层薄硅胶：这可能解释了地震期间主要断层强度较低的原因。
