Catalogue of Earthquake Mechanism and Correlation with the Most Active Seismic Zones in South-Eastern Part of Romania

Abstract

Earthquake mechanism and fault plane solution information is fundamental to determine the stress field and to define seismogenic and active tectonic zones. At the same time, it is a basic input to compute seismic hazard by deterministic approach. The purpose of this paper is to update the catalogue of the fault plane solutions for Romanian earthquakes for the time interval 1998–2012. The catalogue is limited geographically to the Carpathians Orogeny and extra-Carpathians area located in the south—eastern part of Romania. The catalogue comprises 259 intermediate-depth seismic events and 90 crustal seismic events, covering the study time interval. All the existing information is considered and revised. The fault plane solutions of the Vrancea earthquakes generated in a confined sinking plate in the mantle reflect the dominant geodynamic process in the study region. The typical features revealed by all the previous studies on the subcrustal seismic activity (predominant dip-slip, reverse faulting, characterizing both the weak and strong earthquakes) are reproduced as well by our investigation. As concerns the earthquake activity in the crust, a few new refined aspects are highlighted in the present work: (1) a deficit of the strike-slip component over the entire Carpathians foredeep area, (2) different stress field pattern in the Făgăras—Câmpulung zone as compared with the Moesian Platform and Pre-Dobrogean and Bârlad Depressions, (3) a larger range for the dip angle of the nodal planes in the Vrancea subcrustal source, ~400–700 against ~700, as commonly considered.