Hybrid empirical ground-motion model for the Alborz region of northern Iran

Abstract

The Alborz region is situated in northern Iran and is a seismically active region that has experienced several devastating earthquakes. Due to the scarcity of recorded data, only a few Ground Motion Models (GMMs) have been developed explicitly for the Alborz region, and most of the previous GMMs for Iran have been developed for the entire country by combining data from all five seismotectonic provinces. The capabilities of the Hybrid Empirical Method (HEM) in developing GMMs for regions with sparse recorded datasets enable us to develop a new GMM for the Alborz region. In this study, using the HEM approach, we developed a new GMM to predict Peak Ground Acceleration (PGA) and spectral accelerations (SAs) across periods ranging from 0.01 to 10 s in the Alborz region of northern Iran. The dataset comprises 775 acceleration records generated by 167 events, recorded at 309 stations within the range of 1 km < R_jb < 160 km and 3 < M_w < 7.4, from 1980 to 2020. We adopted a simple functional form that is a function of moment magnitudes (M_w) and Joyner-Boore distance (R_jb) for the reference site condition with V_S30 = 760 m/s. This model is applicable for M_w in the range of 3–7.5, R_jb ≤ 200 km, and the reference site condition with V_S30 = 760 m/s.