The SEA99 ground-motion predictive relations for extensional tectonic regimes: Revisions and a new peak ground velocity relation

In this note, we expand on a previous study of strong ground motions in extensional tectonic regimes by Spudich et al. (1999). First, we correct the predictive relations they determined for horizontal peak ground acceleration and 5% damped pseudovelocity response for an approximately 20% overprediction of rocksite data that they noted in their article. Second, we regress data compiled in their study to determine a predictive relation for geometric mean horizontal peak ground velocity. Peak ground velocity estimates are needed to apply some commonly used methods for predicting earthquake damage and Modified Mercalli intensities. However, there are few other recently published predictive relations for peak ground velocity-and none that are specifically designed for use in extensional tectonic regimes.