Earthquake scaling relations are commonly used in seismic and tsunami hazard analysis. These scaling relations implicitly assume the self-similarity of earthquakes regardless of their magnitude. However, for earthquakes that rupture close to the Earth's surface (a.k.a., the free surface), the self-similar assumption doesn't hold. Due to the Earth's surface-fault stress interaction, shallow earthquakes tend to slip more.

Shallow earthquakes pose great threats to humans because of their proximity to our society. It is, therefore, important to characterize the Earth's surface effect on earthquake scaling relations. Such effects have rarely been systematically quantified for megathrust earthquakes, probably due to a lack of computation power and a high-quality finite fault model database. We bridge this gap by conducting a large number of numerical models and analyzing the recently compiled finite-fault-model database SRCMOD (Mai & Thingbaijam, 2014). 

Our results may have implications for explaining the apparently depth-dependent source parameters, and may also help reduce the uncertainties in the seismic and tsunami hazard assessment for large megathrust earthquakes.

Learn more in our publication Wu et al., 2023, GRL and my Oct-2022 presentation slides @USC. 

Last updated Aug-28-2023