Seismic hazard assessment in the Podhale region, Poland—zone and smoothed seismicity approach

Abstract

Poland is characterised by weak natural seismicity. However, the last analysis of the natural seismic hazard in the country was carried out 24 years ago. Therefore, a significant fraction of the recorded seismicity is not included in the hazard estimates currently used, either because recent observations are not taken into account or because of improved seismic network capabilities. Furthermore, Podhale, in the Tatra Mountains, is the only region with recorded permanent natural seismicity. This study aims to create new seismic hazard maps of the Podhale region from a newly compiled database containing information on historical events and two complete instrumental catalogues (regional and local), each at a different level of completeness. The local catalogue was recorded over the last few years. Two seismic hazard assessment techniques were applied, namely the conventional (zone-based) (Cornell in Bull Seismol Soc Am 58(5): 1583–1606, 1968) and the smoothed seismicity model, based on the spatial distribution of seismicity. The earthquake recurrence parameters were estimated using the methodology developed by Kijko et al. (Bull Seismol Soc Am 106: 1210–1222, 2016). The new seismic hazard model incorporates several improvements, such as a comprehensive logic tree and a new set of ground motion models. The new maps provide a more detailed assessment of the seismic hazards of the investigated area. Moreover, they predict higher PGA than previous seismic hazard maps covering Podhale, like global European Seismic Hazard Maps 2013 and 2020.