Earthquake rupture propagation and termination in fault zones with along-strike variation of damage

Yihe Huang, & Julian C. Lozos

Accepted May 14, 2018, SCEC Contribution #8090

Faults are surrounded by a hierarchical structure of damaged rocks. Such damaged fault zones can extend several hundred meters across major faults such as San Andreas, Nojima and North Anatolian faults. They also show along-strike variations of damage that may be correlated with historical earthquake ruptures. Due to the change of energy required for rupture propagation, the fault zone segmentation can either prohibit or assist rupture propagation and significantly affect the final sizes of earthquakes. Recent dense array data recorded at the San Jacinto fault zone suggests the existence of three prominent fault zones across the Anza seismic gap and the south section of the Clark branch, whereas fault zones were not detected near the ends of the Anza seismic gap. We investigate the effects of along-strike variation of fault zone damage using dynamic rupture simulations, which calculate the time-varying rupture process by considering the interactions between fault stresses, friction, and material heterogeneities. We first focus on the along-strike rupture propagation in a 2D configuration. We will show that, for small nucleation sizes and short rupture propagation distances, ruptures tend to terminate when they enter intact rocks outside fault zones. The stopping effect is less pronounced when fault zones become wider, sharper and more damaged, indicating a temporal correlation between the fault zone structure and break-through ruptures. Moreover, break-through ruptures are also expected when a sufficiently-large high-stress asperity exists at the end of the fault zone. We will then present 3D scenarios of San Jacinto earthquake ruptures and investigate whether ruptures can break through the Anza seismic gap given the current stress state and fault zone segmentation. Our results suggest that a priori knowledge of the fault zone segmentation is of great importance for predicting sizes of future large earthquakes on major faults.

Huang, Y., & Lozos, J. C. (2018, 05). Earthquake rupture propagation and termination in fault zones with along-strike variation of damage. Oral Presentation at 2018 Seismology of the Americas Meeting.