The seismicity assessment and probabilistic seismic hazard analysis of the plateau containing large dams around the East Anatolian Fault Zone, eastern Turkiye

Abstract

The earthquake hazard of the wide plateau comprising significant dams around the East Anatolian Fault Zone (EAFZ) in eastern Turkiye is studied by means of the seismicity assessment and probabilistic seismic hazard analysis (PSHA). The fault segments of the EAFZ in the east of Kahramanmaras city, which were previously assigned as a seismic gap, are shown to produce an earthquake in the order of at least M-w = 7.4. b values of the frequency-magnitude distribution calculated from the declustered M-w & GE; 3.2 seismicity after 1995 indicate significant temporal (a gradual decrease from 1.6 to 0.8 between 2010 and 2019) and spatial variations (between 0.75 and 2.1), leading to a short recurrence time estimation of as low as 90 years for an earthquake size comparable to the 2020 Sivrice earthquake (M-w = 6.7). No matter which attenuation relationship is used, the PSHA assuming a 475-year recurrence period results in considerably higher PGA values (average 0.25-0.64 g) as compared to the previous local and regional scale studies, suggesting higher seismic hazard than known so far. The presence of the seismic gap, the decreasing b value as an indication of rising ambient crustal stresses, the estimated shortest recurrence time of 90 years and the computed PGA values imply a significant earthquake hazard for the study area. Considering that the study area contains large cities with historic heritages, important industrial capacities and the existence of big crucial dams, requiring to be on alert in terms of seismic safety and preparedness of the population.