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We present an adjoint-based optimization method to invert for stress and frictional parameters used in earthquake modeling. The forward problem is linear elastodynamics with nonlinear rate-and-state frictional faults. The misfit functional quantifies the difference between simulated and measured particle displacements or velocities at receiver locations. The misfit may include windowing or filtering operators. We derive the corresponding adjoint problem, which is linear elasticity with linearized rate-and-state friction and, for forward problems involving fault normal stress changes, nonzero fault opening, with time-dependent coefficients derived from the forward solution. The gradient of the misfit is efficiently computed by convolving forward and adjoint variables on the fault. The method thus extends the framework of full-waveform inversion to include frictional faults with rate-and-state friction. In addition, we present a space-time dual-consistent discretization of a dynamic rupture problem with a rough fault in antiplane shear, using high-order accurate summation-by-parts finite differences in combination with explicit Runge–Kutta time integration. The dual consistency of the discretization ensures that the discrete adjoint-based gradient is the exact gradient of the discrete misfit functional as well as a consistent approximation of the continuous gradient. Our theoretical results are corroborated by inversions with synthetic data. We anticipate that adjoint-based inversion of seismic and/or geodetic data will be a powerful tool for studying earthquake source processes; it can also be used to interpret laboratory friction experiments.
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This content will become publicly available on August 1, 2026
Geometry of Continuous Adjoint Newton's Method for Bivariate Quadratics
Newton's method is a classical iterative approach for computing solutions to nonlinear equations. To overcome some of its drawbacks, one often considers a continuous adjoint form of Newton's method. This paper investigates the geometric structure of the trajectories produced by the continuous adjoint Newton's method for bivariate quadratics, a system of two quadratic polynomials in two variables, via eigenanalysis at its equilibrium points. The main ideas are illustrated using plots generated by a Maple program.
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- PAR ID:
- 10652988
- Publisher / Repository:
- Maple Transactions
- Date Published:
- Journal Name:
- Maple Transactions
- Volume:
- 5
- Issue:
- 3
- ISSN:
- 2564-3029
- Page Range / eLocation ID:
- 22493
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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