Earthquake “doublets” – case studies for Kresna-Kroupnik (Bulgaria-M7.8) and Gaziantep–Kahramanmaraş (Turkey-M7.8)

The devastating earthquakes (M7.8 and M7.5) on 6th February 2023 demonstrate the power of the nature and weakness and fragility of the human society. Affecting more than 20 million people in Turkey, the death poll reaches about 60 000 deaths and about three times more injured, 120 000 buildings destroyed and more than 60 billion economical losses in Turkey and Syria. This tremendous seismic event at the same time gave the possibility to study and extract the lessons learned and to prevent heavy consequences when next similar event occurred. Following the context of the specific behavior of the seismic process this event can be attributed to the terminology using the word “doubles” of such a combination of two very strong earthquakes occurred in close space and time window – near Gaziantep and Kahramanmaraş.  The two strong earthquakes of 6th February demonstrated all peculiarities of the seismic process and its geophysical, seismological and social consequences. The similar effects have been observed also in 1904 in Bulgaria. On 4th of April, 1904 two very strong earthquakes (M7.2 and M7.8) occurred in a very close time and space domain. These seismic events can also be classified as a “doublet”. So the comparative analysis of such strong earthquakes can help to understand better the seismic process and the following risks for the population, infrastructure and the affected countries as a whole.  This paper is targeted to the comparison of the case studies to the seismic doublets in Bulgaria and Turkey and their peculiarities with a focus on the seismic process, destructions, negative social consequences and the specifics if they exist and to extract knowledge which can be useful for the prevention of all possible negatives.  The results obtained suggest that similar seismic events might have very different geophysical, seismological and social consequences due to the resilience and environmental peculiarities of the specifically affected sites.