Applicability of ground-motion prediction equations to a Greek within-slab earthquake dataset

Abstract

In the present work I investigate the compatibility of the Abrahamson et al. (Earthq Spectra 32:23–44, 2015) and Zhao et al. (Bull Seismol Soc Am 96:898–913, 2006a) ground-motion prediction equations (GMPEs), developed using non-Greek data from subduction earthquakes, with the magnitude, distance and site scaling suggested by a Greek dataset from subduction, within-slab, earthquakes. The dataset is comprised of recordings from force-balance accelerometers as well as broadband seismometers. The motivation for this study comes from (a) the relatively small number of recordings from large subduction, within-slab, events which to a certain extent limits the applicability and accuracy of the regional subduction GMPEs and (b) the necessity of capturing the epistemic uncertainty in the probabilistic seismic hazard studies for the broader Aegean area, which is currently misrepresented due to the small number of available regional or properly adjusted worldwide ground-motion prediction models. For the Abrahamson et al. (2015) model, the analysis shows that the magnitude scaling implied by the dataset requires moderate adjustments to the magnitude terms. The study of intra-event residuals with distance revealed strong positive trends for the back- and negative trends for the fore-arc data, especially at short periods. The original analysis and the evaluation of the adjusted Zhao et al. (2006a) model revealed that the events in the deeper parts of the subduction (D > 140 km) introduce a significant bias to the model, which results in unrealistically high spectral values for events that occur in that shallower parts of the subduction. Consequently, the applicability of the proposed adjusted Zhao et al. (2006a) model, should be limited to events with D < 125 km. The adjusted Abrahamson et al. (2015) and to a certain extend Zhao et al. (2006a) along with the Skarlatoudis et al. (Bull Seismol Soc Am 103:1952–1968, 2013) GMPEs, form a suite of models that accurately describe the ground motions for the Hellenic subduction. The use of these models in future probabilistic seismic hazard studies in the Hellenic subduction zone will adequately represent the current knowledge of subduction GMPEs and result in more realistic estimates of the seismic hazard in the area.