Incorporation of directivity effect in probabilistic seismic hazard analysis and disaggregation of Tabriz city

Abstract

Near-field ground-motion records affected by directivity may show unusual features in the signal resulting in low-frequency cycle pulses in the velocity time history. Current probabilistic seismic hazard analysis (PSHA) is not able to predict such effects well; recent studies thus have proposed modified frameworks to incorporate pulse effect in modified PSHA. This paper attempts to carry out the seismic hazard mapping of Tabriz city according to modified and ordinary PSHA for different return periods. Tabriz, located in northwest of Iran, is situated in the vicinity of the North Tabriz Fault, which is one of the major seismogenic faults. Disaggregation results indicate that including pulse-like effects in PSHA, increases the relative contribution of close distances and small epsilons (ɛ). Another major probable result is the high contribution of pulse periods close to spectral period. The contributions to each earthquake scenario at long-period spectral acceleration shift to larger magnitudes with including the pulse effects.