Stress field evaluation in the earthquake-prone crustal zones of Romania, based on a comprehensive and updated focal mechanisms catalog

Seismic activity in Romania encounters a variety of tectonic domains, from crustal earthquakes, which occur along active faults, to intermediate-depth seismicity that extends down to 200 km depth and which is limited in a small subcrustal seismogenic volume beneath the SE bend of the Carpathians arc. Crustal depth seismicity in Romania is distributed throughout the territory, the areas with important seismic activity and which are also analyzed in this paper being: Vrancea, Fagaras-Campulung, Banat, Dobrogea zones.

Using the polarity of first arrivals methodology (FOCMEC software developed by Havskov et. al 2020), we calculate the focal mechanisms for crustal depth earthquakes that occurred in these areas between 2012 and 2022. We then derive the regional distribution of the stress field through a linear inversion using the focal mechanisms obtained in this study, supplemented by the solutions of the REFMC catalog (Radulian et al 2020). Inversion results vary from the compressive regime in the SE Carpathians bend zone, to strike-slip regime in Banat zone, and extensive regime in Dobrogea area. The stress field configuration is matching generally the configuration of the global stress pattern as shown by the World stress map with the exception of some significant deviations that reflect local conditions. 

The analysis of focal mechanisms as well as the stress field provides a basis for transdisciplinary discussions and collaborations between researchers from various fields.