The SE-Carpathians indicate significant geodynamic activity, especially in the external
part due to the current subduction processes. This part is the so-called Vrancea-zone
where the distribution of the seismic events is quite dense considering the relatively
small area (around 30*70 km).The authors have carried out cluster analyses of the
focal mechanism solutions and their inversions to support the recent and previously
published studies in this region. They have applied different pre-existing clustering
methods – e.g. HDBSCAN (hierarchical density-based clustering for applications with
noise) and agglomerative hierarchical analysis – considering the geographical coordinates,
focal depths and parameters of the focal mechanism solutions of the used seismic events,
as well. Moreover, they have attempted to improve a fully-automated algorithm for
the clustering of the earthquakes for the estimations. This algorithm has only one
optional hyper-parameter which is eligible to detect the outliers from the input dataset.
Due to this, it is possible to reduce the running time and subjectivity. In all cases,
the calculated stress tensors are in close agreement with the previously published
results.
