Refinements to the Graves-Pitarka (GP) Kinematic Rupture Generator

Robert W. Graves, & Arben Pitarka

Submitted August 30, 2026, SCEC Contribution #15263, 2026 SCEC Annual Meeting Poster #TBD

The Graves-Pitarka (GP) kinematic rupture generator provides a fast and efficient approach for creating realistic rupture descriptions used in ground motion simulations, and for many years, it has served as a key component of the SCEC CyberShake and Broadband Platform (BBP) projects. Here we describe recent refinements to the GP methodology aimed at improving the fidelity of simulated high-frequency (5-10 Hz) near-fault ground motions. First, we incorporate depth-dependent slip-correlation lengths so that slip variation along the shallow portion of the rupture (upper 5 km) is considerably smoother than at depth. This builds upon other depth-dependent features in the GP method that limit the strength of high-frequency energy along the shallow fault, and also follows a parameterization where deeper, more compact asperity regions radiate the strongest motions (e.g., Irikura and Miyake, 2011; Frankel, 2018). Second, we scale local rise time directly with local slip and use average slip, rather than seismic moment, to set the average event rise time; this limits the dynamic stress drop from becoming unrealistically large, particularly for events with high static stress drop. Third, we develop a down-sampling approach that reduces the number of subfaults while preserving an accurate representation of higher-frequency radiation, significantly increasing computational efficiency for Green's function-based simulations such as CyberShake and BBP. Using the updated rupture generator, we simulate near-fault ground motions (0 to 10 Hz) for a suite of Mw 7.0, 7.5, and 7.8 strike-slip events. The simulated responses show good agreement with spectral acceleration estimates from NGA-West2 empirical ground motion models across the period band of 0.1 to 10 s. The simulations also replicate observed frequency-dependent scaling of very near-fault (1-5 km) ground motions, including the magnitude saturation of ground motions with increasing frequency and the negative correlation of high-frequency ground motion level with increasing surface fault displacement.

Key Words
kinematic rupture, strong ground motion, simulation

Citation
Graves, R. W., & Pitarka, A. (2026, 08). Refinements to the Graves-Pitarka (GP) Kinematic Rupture Generator. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Ground Motions (GM)