Using a grid-search approach to validate the Graves-Pitarka broadband simulation method

Robert Graves

doi:10.1186/s40623-022-01742-y

Using a grid-search approach to validate the Graves-Pitarka broadband simulation method

Earth, Planets and Space

By: Robert Graves

https://doi.org/10.1186/s40623-022-01742-y

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Abstract

This work assesses the ability of the Graves–Pitarka simulation approach to reproduce observed ground motions for 12 California and Baja California earthquakes. A total of 240 realizations are computed for each earthquake and compared with recorded strong motions from near-fault sites. In addition to spatial variability in slip, each realization samples from discrete combinations of average rupture speed, rise time, and down-dip fault width. Ground motions for each realization of a given earthquake are compared to the observations using a pseudo-spectral acceleration goodness-of-fit (GoF) metric. Parameters for the lowest misfit cases are then tabulated to develop relations for estimating median values and ranges for future applications. The results are generally consistent with published scaling relations for estimating rupture dimensions as a function of magnitude. Additionally, I find the average rise time scales as ${2.3 \times α}_{T} \times 10^{- 9} {\times M}_{o}^{1 / 3}$ (M_o is seismic moment in dyne-cm) and average rupture speed as $(0.765 \pm 0.075) \times α_{T}^{- 1} \times V_{s}$ (V_s is local shear wave velocity), where ${2.3 \times α}_{T} \times 10^{- 9} {\times M}_{o}^{1 / 3}$ is a mechanism adjustment ranging from a value of 1.0 for pure strike-slip to 0.9 for pure reverse-slip cases. There are cases where slightly different combinations of parameters produce equally good fits to the observations, demonstrating the non-uniqueness of using a single GoF metric in this approach. Nonetheless, the results reinforce the importance of adequately sampling ranges of rupture parameters when performing validations, as well as when simulating ground motions for future events.

Additional publication details
Publication type	Article
Publication Subtype	Journal Article
Title	Using a grid-search approach to validate the Graves-Pitarka broadband simulation method
Series title	Earth, Planets and Space
DOI	10.1186/s40623-022-01742-y
Volume	74
Year Published	2022
Language	English
Publisher	Springer
Contributing office(s)	Earthquake Science Center
Description	186, 26 p.
Google Analytic Metrics	Metrics page