Contents lists available at ScienceDirect Soil Dynamics and Earthquake Engineering journal homepage: www.elsevier.com/locate/soildyn Seismic hazard analysis using simulated ground-motion time histories: The case of the Sefidrud dam, Iran H. VahidiFard a, ⁎ , H. Zafarani b , S.R. Sabbagh-Yazdi a , M.A. Hadian c a K. N. Toosi University of Technology, 470 Mirdamad Ave. West, P.O. Box: 15875-4416, Tehran 19697 64499, Iran b International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran c University of Tehran, 16th Azar St., Enghelab Sq., Post Office Box: 14155-6619, Tehran 14174 66191, Iran ARTICLE INFO Keywords: Probabilistic seismic hazard analysis Sefidrud dam Background seismicity Strong motion Hybrid broadband simulation Near-field ABSTRACT This study aims at conducting probabilistic seismic hazard analysis for the Sefidrud dam located near Rudbar City. For this purpose, firstly, the characteristic earthquake recurrence model for major earthquakes on individual main faults have been combined with the smaller (smoothed) background seismicity of the region. Then, appropriate ground motion prediction equations were applied to estimate hazard values. Finally, in order to obtain reliable estimation of seismic hazard due to sources close to the dam site and to investigate near-field characteristics of motion, the Rudbar fault as the most prominent earthquake source in the immediate vicinity of the site is considered in seismic hazard computation using hybrid broadband simulation based ground motion parameters. The results of this method with different declustering schemes are reported for two level of seismic hazard analysis (i.e. return periods of 475 and 2475 years). Best estimate seismic hazard maps of PGA and PGV values obtained from the logic tree method is presented. By inclusion of simulation results for the Rudbar fault in the probabilistic seismic hazard analysis (PSHA), maximum PGA and PGV for 475 years return period obtained around 340 cm/s/s and 25 cm/s, respectively. For classic PSHA without including simulation the maximum PGA and PGV for 475 years return period obtained around 450 cm/s/s and 32 cm/s, respectively. With the simulation-based PSHA for a 2475 years return period a maximum PGA of 650 cm/s/s and PGV of 50 cm/s have been estimated. Classic PSHA (without simulation) for a 2475 years return period has resulted a maximum PGA of 850 cm/s/s and PGV of 65 cm/s. 1. Introduction The Rudbar strike-slip fault lies in the Alborz Mountains. The Alborz forms a high curve of mountains from the southern end of the Talesh (~37°N49°E) to their intersection with the Kopeh Dag at about 56°E. No earthquakes deeper than 30 km is reported correctly in the Kopeh Dag, Alborz and Talesh, which limited to the northeast, south and west sides of the South Caspian Basin (beneath the central Caspian Sea). The Rudbar fault is situated over 2,000 m from sea level, and close to the crest of the western Alborz [1] (Fig. 1). The Rudbar earthquake is one of four large magnitude events occurred in this part of the Alborz during the instrumental period (Table 1). The damage distribution of the Polrud-Tonekabon earth- quake suggests the east–west Kelishom left-lateral fault, which is located east of the Rudbar fault, as a possible source. The Rudbarat- Taleqan earthquake may have ruptured the Alamutrud fault farther east. Apparent left-lateral river displacements of ∼200 m on the Kashachal fault and up to ∼1.5 km of the Kelishom fault, which are situated at the eastern end of the Rudbar fault [2]. The Rudbar earthquake of the 20 June 1990 with moment magnitude of 7.30 and a seismic moment of 1.4 × 10 N. m 20 (total left- lateral displacements are a maximum of ∼1 km) was the most catastrophic earthquake occurred in northern Iran. The study of Iranian historical earthquakes confirms occurring destructive seismic events in this region during historical times [2–7]. In Table 1 is summarized three historical events struck the vicinity of Rudbar with their causative faults. These earthquakes with the surface magnitude ranging from 7.2 to 7.7 are comparable to the Rudbar earthquake [5]. According to Campos et al. [45]: "Several authors have reported that the body-wave signals for the Rudbar earthquake indicated that rupture was very complex. For example, Berberian, Qorashi, Jackson, Priestley and Wallace [5] quote an unpublished work by Gao and Wallace (1992) http://dx.doi.org/10.1016/j.soildyn.2017.04.017 Received 22 August 2016; Received in revised form 9 April 2017; Accepted 19 April 2017 ⁎ Corresponding author. E-mail addresses: hesam_vf@yahoo.com, hvahidifard@mail.kntu.ac.ir (H. VahidiFard), h.zafarani@iiees.ac.ir, hamzafarani@yahoo.com (H. Zafarani), m.a.hadian@hotmail.com (M.A. Hadian). Soil Dynamics and Earthquake Engineering 99 (2017) 20–34 0267-7261/ © 2017 Published by Elsevier Ltd. MARK