A method for dissipating energy in elastic dynamic earthquake rupture simulations: Non-linear radiation damping

Ruth A. Harris, & Michael J. Barall

Published September 10, 2023, SCEC Contribution #13135, 2023 SCEC Annual Meeting Poster #102

We introduce 'non-linear radiation damping', a new mechanism that dissipates energy in elastic dynamic rupture simulations and results in more realistic ground motions and slip velocities, while not requiring the large number of assumed variables in viscoplastic methods. Computational simulations of dynamic earthquake rupture help us learn about earthquake source behavior and the resulting ground motions. A challenge with these types of simulations is that they require many assumptions, including the fault geometry, the fault friction constitutive laws, the rock properties, and the initial stress conditions. Although we have some information about these parameters, much of the information is unknown. This requires modelers to make many assumptions, with one of the most common assumptions being that rocks respond elastically to sudden changes in stress and strain. An elastic rock response is helpful in that it allows for a simplification of the initial stress conditions. However, an elastic rock response can also lead to simulated on-fault slip rates and off-fault ground motions that are faster than those inferred from earthquake observations. Our work provides a solution to this problem. We propose a new method, which we call ‘non-linear radiation damping’. The implementation is simple, and just requires adding the non-linear radiation damping term to the friction formulation. The result is slower on-fault peak slip rates and ground motions, similar to what might be achieved by incorporating a complex viscoplastic framework, but without the need to assume values for a variety of unknown features such as the initial stress conditions and rock yielding parameters at all locations in an earthquake region.

Reference:

Barall, M., and R.A. Harris (2023), Nonlinear radiation damping: A new method for dissipating energy in dynamic earthquake rupture simulations, The Seismic Record, 3(2), 69–76, doi:10.1785/0320230001

Key Words
earthquake source, dynamic rupture, inelastic yielding, ground motion, earthquake physics

Citation
Harris, R. A., & Barall, M. J. (2023, 09). A method for dissipating energy in elastic dynamic earthquake rupture simulations: Non-linear radiation damping. Poster Presentation at 2023 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)