Seismicity and seismic hazard parameters evaluation in the island of Crete and the surrounding area inferred from mixed data files

A study of the spatial distribution of seismicity and seismic hazard is undertaken for Crete and the surrounding area (CISA). For the estimation of seismicity parameters, CISA is divided in rectangular subregions. By applying the centroid of strain energy technique, we obtain seismicity parameter maps closely related to the tectonics of the area. The b-value from the magnitude–frequency distribution is calculated by a maximum likelihood technique ( Page, 1968. Bull. Seism. Soc. Am. 58, 1131–1168), as well as by Gumbel's first asymptotic distribution of extreme values technique. The b-value shows consistent spatial variation along CISA for both techniques. Low b-values are dominant in the western part of CISA, while higher b-values are present to the east side, forming a pattern like a ‘sleeping letter S’. This pattern may be attributed to the variation of the regional velocity of deformation. Finally, we performed seismic hazard analysis for shallow and intermediate events. From mixed (historical and instrumental) data files, we estimated the regional maximum magnitude M̂ max, as well as the other parameters like the activity rate of seismic events λ̂ and the well-known b̂ parameter ( Kijko and Sellevoll, 1989. Bull. Seismol. Soc. Am. 79, 645–654).