Probabilistic Seismic Hazard Assessment for Izmir, Turkey AYKUT DENIZ, 1 KASIM ARMAGAN KORKMAZ, 2 and AYHAN IRFANOGLU 3 Abstract—Izmir, the third largest city and one of the major economic centers in Turkey, has more than three million residents and one-half million buildings. The city, located in a seismically active region in western Anatolia, was a subject of the 1997 RADIUS (Risk Assessment Tools for Diagnosis of Urban Areas against Seismic Disaster) project. In this paper, the seismic hazard of Izmir is investigated through probabilistic seismic hazard assessment. First, the seismic setting of Izmir is presented. Con- sidering the statistics of earthquakes that took place in the region during the period 1900–2005, a simple seismic hazard model is used to facilitate the assessment. To account for modeling uncer- tainties associated with the values of seismicity parameters, a logic tree procedure is employed in carrying out the seismic hazard computations. The resulting weighted average seismic hazard, presented in terms of peak ground acceleration and associated probability of exceedence, could be considered the ‘‘best estimate’’ of seismic hazard for Izmir. Accordingly, for a return period of 475 years, for rock sites, a PGA value of 0.34 g is calculated. This PGA hazard estimate is close to the current code-recommended design acceleration level for Izmir. Key words: Seismic hazard assessment, seismic hazard analysis, earthquake, Izmir. 1. Introduction Heavy destruction caused by recent earthquakes in Turkey has increased interest in seismic hazard and risk assessment of urban areas in Turkey (SCHNEIDER and SCHAUER, 2005). Various researchers have reported that the seismic risk exposure of Izmir is very high (EMRE et al., 2005;ILHAN et al., 2004; RADIUS, 1997;KORKMAZ et al., 2009). Following the RADIUS investigation in 1997, an earthquake master plan for Izmir was published by the Metropolitan Municipality of Izmir (MMI, 2000). Recent studies (ERDIK et al., 2004;KORKMAZ et al., 2009) indicate that this third largest city in Turkey, with its rapidly increasing population and built environment, is fac- ing very high seismic risk. The pioneering study on seismic hazard estima- tion was carried out by CORNELL (1968). While Cornell’s work still describes the procedure ade- quately, GUPTA (2002) provides the current state-of- the-art format of seismic hazard analysis in detail. The current earthquake zoning map of Turkey is based on the study of GULKAN et al.(1993). Later, ERDIK et al.(1999) and BOMMER et al.(2002) con- tributed, in particular to the seismic zoning part of the analysis, and GULKAN and KALKAN (2002) developed a domestic earthquake attenuation model consisting of a set of equations based on the records of the 1999 Marmara and Duzce earthquakes. None of these studies specifically focus on the seismic hazard or seismic loss in the Izmir metropolitan area, but obviously results of some of the latter studies are utilized as tools in our study, too. In what follows, the seismic hazard of Izmir is investigated by presenting the seismic setting, con- sidering the statistics of earthquakes that have taken place in the region and employing a logic tree proce- dure to account for modeling uncertainties associated with the values of seismicity parameters in our study. The current study contributes to previous studies by providing extensive information on the seismicity and seismic hazard in Izmir and its surrounding region. First, all of the historic and instrumented era earthquake event records currently available in the international databases were taken into consideration. The earthquakes were usually reported by different sources using different magnitude scales. This prob- lem was resolved through cross-checking the 1 Technological Engineering Services Co. Ltd, Perge Blvd., 115/5, Antalya, Turkey. 2 Department of Civil Engineering, Suleyman Demirel University, Isparta, Turkey. E-mail: armagan@mmf.sdu.edu.tr 3 School of Civil Engineering, Purdue University, West Lafayette, IN 47907, USA. Pure Appl. Geophys. Ó 2010 Birkha¨user / Springer Basel AG DOI 10.1007/s00024-010-0129-6 Pure and Applied Geophysics