Analysis of pulse-like ground motion recordings from Vrancea intermediate-depth earthquakes

This short study focuses on the analysis of pulse-like ground motion recordings originating from Vrancea intermediate-depth earthquakes. A ground motion database of 94 horizontal recordings from five Vrancea earthquakes occurring in the period 1977–2004 and having peak ground velocities larger than 10 cm/s in used in this study. The analysis shows that about one-third of the selected horizontal components can be classified as pulse-like. In addition, the recordings were obtained on both soft and stiff soil sites situated at epicentral distances of up to 160 km. It was also observed that the pulse-like ground motions occur for all the earthquake magnitudes in the database. The analyses have also revealed that the difference between the pulse period of the as-recorded components and of the rotated components is of less than 5%. Finally, an empirical model for the pulse period of ground motion recordings from Vrancea intermediate-depth earthquakes is proposed.