The Existence and Cessation of the Free-Surface-Induced Supershear Rupture: Depth-Dependent Stress Effects

Date: 4/25/2019

Time: 11:15 AM

Room: Elliott Bay

It is well known that rupture on a strike-slip fault can accelerate to supershear rupture speed when it encounters the free surface and continues to propagate, which is termed the free-surface-induced supershear rupture. However, through 3D dynamic rupture simulations, we find that this effect is strongly dependent on the fault stress conditions. For a homogeneous stress distribution, the background normal stress plays a key role in the initiation of the free-surface-induced supershear rupture. A low initial normal stress may prevent the initiation of the free-surface-induced supershear, causing the rupture to propagate at sub-rayleigh speed. Depth-dependent initial stress, which is likely more realistic in nature, is another important factor controlling the appearance of the free-surface-induced supershear rupture. The free-surfaced-induced supershear rupture may be constrained to the layer close to the free surface under certain conditions, and may even transition back to sub-shear rupture propagation after an ephemeral supershear period. Our work may provide a physical explanation for the somewhat rare observations of free-surface-induced supershear rupture in nature.

Presenting Author: Feng Hu

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