A Sensitivity study for probabilictic seismic hazard assessment of Sinop nuclear power plant site

Yılar, Erkan
Based on the studies conducted for more than 40 years, Sinop is chosen as one of the three most convenient places in Turkey to construct a Nuclear Power Plant (NPP). The objective of this study is to evaluate the sensitivity of the design ground motions for Sinop NPP Site to the seismic source characterization and ground motion prediction models within the probabilistic seismic hazard assessment (PSHA) framework. This study introduces significant improvements over the previous seismic hazard studies conducted for the Sinop NPP in terms of seismic source characterization models. Based on the regulations of Turkey, United States and International Atomic Authority, the seismic sources located within the 320 km radius around the Sinop NPP site; North Anatolian Fault (NAF) Tosya- Erbaa Segment (1942-1943 earthquakes rupture zone), Abant-Ilgaz Segment (1944 Rupture), Erzincan Segment (1939 Rupture), Esençay - Merzifon Fault Zone, Sungurlu Fault, Ekinveren Fault, Erikli Fault, Balıfakı Fault and Pontic Escarpment Zone were investigated. To develop the planar source characterization models, geometries of the fault segments (length, width, dip angle and segmentation points) were determined with the help of previously conducted site studies, new fault maps and previous studies in the literature. Fault segments, rupture sources, rupture scenarios and fault rupture models were determined using the USGS Working Group (2003) terminology. To properly represent the characteristic behavior, planar fault segments were defined with composite magnitude distribution model and multi-segment ruptures were considered. The Pontic Escarpment Zone and Sungurlu Fault were modeled as areal sources using truncated exponential magnitude distribution model. The sensitivity of the hazard results to the parameters of seismic source models was analyzed for each source to illustrate the needs for further site studies for Sinop NPP. This study makes the first attempt to characterize the ground motions and its variability for Sinop NPP site. Several local, global and regionalized candidate ground motion prediction models (GMPEs) were proposed and evaluated. After a detailed evaluation of median predictions and resulting hazard curves, four NGA models and two TR-adjusted NGA models were used for the ground motion characterization of the Sinop NPP site. Equal weights are assigned to the global and regionalized NGA models. Results of the study are presented in terms of a range of hazard curves for the peak ground acceleration since the site surveys and ground motion characterization efforts are not yet finalized. These results will be refined by the help of the newly obtained site data in the next few years.