Published February 18, 2021 | Version v1
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CRUSTAL STRESS FIELD IN THE ACTIVE SEISMIC ZONES IN AND AROUND VRANCEA AREA, ROMANIA

Creators

  • 1. National Institute for Earth Physics, 12, Calugăreni St., Măgurele, Ilfov, Romania

Description

The mechanisms involved in the geodynamic evolution and the links with present day seismicity in and around an active orogenic area such as Vrancea area, located at the arc bend of the South-Eastern Carpathians in Romania, are of fundamental importance for studies concerning the seismic hazard assessment in Romania. The task is attempted through the partitioning of seismic events and corresponding stress at crustal level in and around the Vrancea zone. We start in this respect with the configuration of seismogenic zones as defined in previous investigations and then we use all the available and reliable earthquake focal mechanisms to study present-day deformation and stress. The goal of the present paper is to investigate the stress field characteristics in relation to the specific geotectonic and seismogenic zones in Vrancea and neighboring areas. The principal stress components are computed by inverting the fault plane solutions provided by a completed and updated catalogue for the crustal earthquakes recorded from 1952 up to 2012. Our investigation is justified to the extent that the basic hypothesis of adequately representing the seismic area partitioning by individual clusters of events is relevant at the scale of each earthquake-prone area and from statistical point of view (minimum 25 – 30 events/active zone). The results obtained through the inversion procedure show that the focal mechanisms are kinematically compatible with the selected clusters (earthquake-prone areas) despite an apparent scattering of the fault plane solutions. For example, the specific thrust faulting regime (compression) in the seismogenic zones in the Vrancea area and extensional stress regime as we go away from the Vrancea area. Note also the general lack of strike-slip faulting, except the seismogenic area located along the Peceneaga–Camena fault, which separates the Scythian platform to the north-east from the Moesian platform to the southwest. All the relevant information obtained in the process of inversion is further used in order to analyze the geodynamic evolution of the active seismic zones around Vrancea area and to try to improve the understanding of some geophysical observations that still do not have a satisfactory explanation in the light of existing models. The assessment of the stress field configuration based on improved and updated focal mechanism data led to a real improvement of the shape of the regional field as computed in the last version of the World Stress Map (WSM 2016).

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References

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