The effects of sediments on supershear rupture have been discussed. Two sediment models with different media properties have opposite effects on supershear rupture. The rupture accelerates into supershear more easily if the sediment is thin in the model with a relatively low wave velocity. In contrast, the supershear rupture transition occurs more easily if the sediment is thick in the model with a relatively high wave velocity. Supershear is first triggered at the lower boundary of the sediment if the initial stress is sufficiently high. Otherwise, supershear is prevented or triggered at the free surface if the initial stress is relatively low. A deep hypocenter favors supershear rupture. The very long supershear transition distance in some cases may explain the extremely long supershear transition distance in the 2001 Kunlunshan earthquake. We also investigate the effects of the depth-dependent stress on the supershear rupture and find that similar results are concluded. Besides, a daughter crack is triggered but propagates in a subshear regime in some cases. A multi-layered sediment model makes it easier to trigger supershear rupture in relative high-velocity sediment but harder in relatively low-velocity sediment. Our results provide a possible explanation for the rarity of supershear earthquakes in nature.

讨论了沉积物对超剪切破裂的影响。两种具有不同介质特性的沉积物模型对超剪切破裂具有相反的影响。如果模型中的沉积物稀薄且波速相对较低，则破裂更容易加速至超剪切作用。相反，如果模型中的沉积物较厚且波速较高，则超剪切断裂过渡会更容易发生。如果初始应力足够高，则首先在沉积物的下边界触发超剪切。否则，如果初始应力相对较低，则会在自由表面上阻止或触发超剪切。较深的震源有利于超剪切破裂。在某些情况下，超长的过渡距离非常长，这可以解释2001年昆仑山地震中超长的过渡距离。我们还研究了深度相关应力对超剪切断裂的影响，并发现了相似的结论。此外，在某些情况下会触发子裂纹，但会在亚剪切状态下传播。多层沉积物模型使得在较高速度的沉积物中更容易触发超剪切破裂，而在较低速度的沉积物中则较难触发。我们的结果为自然中的超剪切地震的稀有性提供了可能的解释。