The effects of sediments on supershear rupture
Jiankuan Xu, Zhenguo Zhang, Xiaofei Chen
Abstract
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.