Collaborative Research (USC/UCLA/UCR/SDSU): Continuing Study of Internal Structure, Dynamic Rupture and Post-Earthquake Healing of the Hector Mine Rupture Zone

提案题目：合作研究（USC/UCLA/UCR）： Hector矿山破裂带的内部结构、破裂和震后愈合的持续研究。作者：李永刚，John E. Vidale, David D. oglesby1999年加利福尼亚Hector矿M7.1级地震，利用断层陷波对地震后愈合、断裂带过程和动态破裂进行研究。利用Hector矿区地表破裂线阵列记录的余震和爆炸产生的断裂带捕获波的观测和FD模拟，揭示了沿断裂带的约100 m宽的低速波导，以及在发震深度的北部破裂分岔。我们之前的工作也表明，这种低速波导自主震以来已经愈合，P波和S波速度在2000年至2001年间增加了约1%。继续监测赫克托地雷破裂区的愈合将帮助我们了解其愈合速度是否随着时间的推移而减慢，就像兰德斯的愈合速度一样。在本文中，我们将1)在2003年重复实验，以进一步发现故障愈合的时空依赖性；2)建立了基于裂缝扩容理论和化学密封理论的断裂愈合力学模型；3)模拟多断裂带的动态破裂，并将这些模型与断裂带岩体的破坏程度联系起来；4)利用剪切波分裂研究近断层应力状态及其时间变化；5)对比Hector Mine和Landers的断层愈合情况，了解平行断层系统中的断层相互作用。通过这个项目，我们将更好地了解断裂带内部结构、破裂过程和地震周期之间的关系。断层结构时空变化的知识将有助于解决断层强度变化的更现实的宏观表示和断层段和断层网络的动态响应，以及预测未来地震的行为。

Proposal Title: Collaborative Research (USC/UCLA/UCR): Continuing Study of Internal Structure, Rupture, and Post-Earthquake Healing of the Hector Mine Rupture Zone.NSF Proposal Number: EAR-0229324, 0229452, 0229678Principal Investigators: Yong-Gang Li, John E. Vidale, and David D. OglesbyABSTRACT We propose to continue our study of post-earthquake healing, fault zone process, and dynamic rupture of the 1999 M7.1 Hector Mine, California, earthquake using fault-zone trapped waves. Observations and FD simulations of fault-zone trapped waves generated by aftershocks and explosions, and recorded at linear seismic arrays deployed across the Hector Mine surface rupture, have revealed a ~100 m wide low-velocity waveguide along the rupture zone, and the bifurcation of northern rupture at the seismogenic depth. Our previous work has also shown that this low-velocity waveguide has healed since the mainshock, with P and S wave velocities increasing by ~1% between 2000 and 2001. Continued monitoring of healing in the Hector Mine rupture zone will help us to see if its healing rate slows with time, as did the healing rate at Landers. In the present proposal, we shall 1) repeat the experiment in 2003 to find further evidence of the time- and spatial-dependence of fault healing; 2) develop a mechanical model based on crack dilatancy theory combined with chemical sealing for interpretation of fault healing; 3) simulate dynamic rupture on multiple fault segments and relate these models to the extent of damage to the rock mass in fault zone; 4) analyze shear-wave splitting for study of the near-fault stress state and its temporal variation; 5) compare the fault healing at Hector Mine with that at Landers for understanding the fault interaction in a parallel-fault system. Through this project, we will obtain a better understanding for the relationships between the fault zone internal structure, rupture process, and earthquake cycle. Knowledge of spatial and temporal variations in the fault structure will help resolve more realistic macroscopic representations of fault-strength variations and the dynamic response of fault segments and fault networks as well as predict behavior of future earthquake.