Observed Pulse-Like Ground Motion and Rupture Directivity Effect in Taiwan Ground Motion Dataset

Observed Pulse-Like Ground Motion and Rupture Directivity Effect in Taiwan Ground Motion Dataset

In this study, we analyze around 40,000 available three-axis ground motion records in the Taiwan ground motion database by using a pulse indicator. Up to 200 records are identified as pulse-like ground motion with horizontal or vertical velocity pulses. We also analyze the record-specific residual of each record from approximately 300 events in the Taiwan ground motion database. Significant rupture directivity effect can be observed in several earthquakes, e.g., the 2010 JiaXian Earthquake, the 2013 NanTou Earthquake, and the 2016 Mei-Nong Earthquake. Unlike observations from the residual analysis of the NGA-West 2 Project database, we find that the rupture directivity affects the ground motion intensity not only for long-period but also for short-period spectral acceleration. We show that involving the rupture directivity model in the current ground motion model can improve ground motion prediction accuracy significantly, especially for earthquakes with strong rupture directivity effects. We also reveal that around 70% of the pulse-like ground motion records occur within ±55 degrees of the rupture directivity in the azimuthal direction. This helps in the prediction of pulse-like ground motion for future earthquakes. Methodology about how to consider the impact of the rupture directivity effect and near-fault pulse-like ground motion on ground motion intensity are proposed based on the observations in this study.