Pulse-like ground motions: Statistical characteristics, and GMPE development for the Iranian Plateau

This research attempts to study the pulse-like ground motions, recorded on the Iranian plateau, and propose predictive equations for simulating the main features of this type of signal. In this regard, firstly, the statistical characteristics of pulse-like records of the Iranian database, containing 770 events and 1206 accelerograms, are statistically investigated. The probability density function of facing a pulse-like signal, for a given location, is obtained, and the main features of acceleration and velocity spectra of these signals are evaluated for the horizontal and vertical directions. Interestingly, the mean value of vertical to horizontal ratio of spectral acceleration of signals reaches above one in many cases. In the next part, a set of ground motion prediction equations are presented for simulating the major properties of velocity pulse itself, including the amplitude, period, and the occurrence time during the recorded time series. Besides to these equations, another set of GMPEs is proposed for generating the 5% damped spectral acceleration of the horizontal and vertical pulse-like ground motions simultaneously considering their component's correlation. These newly developed equations are compared and validated with the existing GMPEs of the Iranian plateau. All of the suggested equations are applicable for the magnitude between 4.0 and 6.5, the site-to-source distance of 2 km-100 km, the focal depth of 2-40 km, and the shear wave velocity of underlying soil varying between 200 m/s to 900 m/s.