Role of fault maturity on relationship of surface displacement and rupture length

Yongfei Wang, & Christine A. Goulet

Submitted August 13, 2021, SCEC Contribution #11352, 2021 SCEC Annual Meeting Poster #261

Following the pioneering work from Scholz (1982) who noted that fault ruptures can extend to lengths far beyond seismogenic depths, scientists have proposed multiple theories and models to provide an explanation, relating fundamental fault rupture parameters to support the observations. The problem, however, is constrained by limited data and remains largely unsolved. Addressing this issue can have important implications for the dominant physics underlying earthquakes spanning a wide magnitude range. Additionally, it may contribute to improved seismic hazards as magnitude-area (or length) scaling relations play a central role in earthquake rupture forecast. In this study, we explore whether knowing the stress drop or the paleoseismic slip rate on a fault (as a proxy of fault maturity) inherently affecting fault properties across multiple scales, improves the modeling of observed fault displacement of shallow continental strike-slip earthquakes and provides a better understanding the role of fault maturity in the relationship between the surface displacement and rupture length. We first aggregate the fault displacement databases of Biasi et al. (2013) and from the Fault Displacement Hazard Initiative (Sarmiento, et al., 2019), along with the slip rate dataset of Anderson et al. (2017), which together include 48 strike-slip earthquakes. To model the estimated average displacements, we adopt the method of envelope averaging by Biasi et al (2013) for all the datasets. We consider a physics-based surface rupture model modified from Shaw (2013) that incorporates a term of slip-rate-related stress drop to account for the effect of the fault maturity. We then perform a regression analysis that includes coefficient uncertainty, and we find that the stress drop has a power-law relationship with the slip rate, with a negative exponent that is different for creeping and non-creeping faults. This relationship is then verified using a spring slider cycle simulation that accounts for fault-maturity-related loading rate and stiffness. We also find that the ratio between the average surface and deep displacements is found to increase with the slip rate (fault maturity) implying that a mature fault has a higher degree of slip localization to the surface. Our presentation summarizes our approach and preliminary findings.

Key Words
Fault maturity; Surface rupture

Citation
Wang, Y., & Goulet, C. A. (2021, 08). Role of fault maturity on relationship of surface displacement and rupture length. Poster Presentation at 2021 SCEC Annual Meeting.


Related Projects & Working Groups
Earthquake Forecasting and Predictability (EFP)