Stable recovery of coefficients in an inverse fault friction problem

We consider the inverse fault friction problem of determining the friction coefficient in the Tresca friction model, which can be formulated as an inverse problem for differential inequalities. We show that the measurements of elastic waves during a rupture uniquely determine the friction coefficient at the rupture surface with explicit stability estimates.
Comment: Final version with added details and corrections, to appear in Arch. Ration. Mech. Anal