Among natural disasters, earthquakes dominate with regard to their social and economic effects on human life and the urban environment. Appropriate risk reduction strategies can be developed only with a better understanding of seismic hazards as well as the population and building growth rates in the corresponding region. In the present study, deterministic and probabilistic earthquake (seismic) ground-motion scenarios are developed and presented for one of the most earthquake-prone cities in Bulgaria, the city of Plovdiv. We apply a method for integrating the spatial distribution of seismic hazards with human exposure to assess hazard impacts. Earthquake scenarios and social vulnerability metrics are combined in a geographic information system (GIS) to identify the spatial vulnerability of the exposed population to seismic risk and the locations for targeting mitigation actions in areas with high exposure and vulnerability levels. The results of our study show that most of the territory of the city is classified at the highest seismic hazard level: PGA 0.2. High and major levels were estimated for the population exposure index (PEI) for nearly 60% of the residential buildings in the city (inhabited by approximately 96% of the Plovdiv population). The spatial distribution of the results is available in GIS format and can be used in scientific and practical applications to reduce the risk and consequences of possible strong earthquakes in future.

The devastating earthquake with moment magnitude MW7.8, (local magnitude ML=7.5) which occurred in the East Anatolian Fault Zone, westwards of Gaziantep, Turkey on February 6, 2023 was followed by an intensive aftershock activity. Studying time distribution of aftershocks is important for understanding physics of the earthquake generation process. In the present study temporal pattern of aftershock sequence of the 2023 MW7.8 Turkey earthquake is analyzed. Because of the factors such as location and radiation pattern and the cumulative nature of building damage, aftershocks can cause more damage than the main shock. The temporal clustering of aftershocks is a dominant non-random element of the seismicity, so when the clusters are removed, the remaining activity can be modelled (as first approximation) as a Poisson process. On the assumption that aftershocks are distributed in time as a non-stationary Poisson process, we use the maximum likelihood method for estimating the parameters (K, c and p) of the modified Omori formula. For testing the goodness of fit between the aftershock occurrence and different statistical models, a transformation from the time scale t to a frequency-linearized time scale τ is applied. Akaike's information criteria is used to select the best model for the temporal distribution of aftershocks. It has been found that temporal distribution of the 2023 Turkey earthquake aftershocks is dominated by the classic power law decay in time and suggests the existence of secondary aftershock activity.