Poster #177, Fault and Rupture Mechanics (FARM)

The effects of Absolute Friction Level on Shallow Fault Dynamics

David D. Oglesby, Baoning Wu, Christodoulos Kyriakopoulos, & Kenny J. Ryan
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Poster Presentation

2021 SCEC Annual Meeting, Poster #177, SCEC Contribution #11658 VIEW PDF
Earthquakes that rupture up to the Earth’s surface pose significant threats to populations. However, our quantitative understanding on how the free surface affects earthquake rupture is still incomplete. At present, modelers still heavily rely on the relationships and intuition obtained in full space models to design experiments and interpret the results. For example, it is well known that in a full space with a symmetric fault, the level of absolute stress and friction has no effect on earthquake dynamics; it is the drop in stress that matters. However, some studies show that the absolute friction level could control the dynamic rupture behavior for a shallow-buried thrust fault model, wher...e there is a feedback between normal and shear stresses (e.g., Oglesby et al., 1998, Scala et al., 2018). In this study, we use dynamic rupture models to explain the role of absolute friction level in rupture behaviors, particularly in the shallow part of the crust where the Earth’s free surface may have a controlling role. Our results imply that when the thrust fault is buried deeply, the absolute friction and stress level have no influence on the final slip if the stress drop and S (strength excess divided by stress drop) are the same, as expected from full-space models from before. However, when the thrust fault ruptures up to near the free surface, the high absolute friction/stress model has a larger slip. The earthquake models we have may help in the interpretation of other dynamic earthquake simulations, as well as the slip in past and future real-world earthquakes.