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SEISMICITY AND SEISMOTECTONIC PECULIARITES IN THE SOUTH-EASTERN PART OF PANNONIAN BASIN. A CASE STUDY: BANLOC-VOITEG SEISMOGENIC STRUCTURE (ROMANIA)

Eugen Oros

Abstract

The paper presents a detailed analysis of the seismic activity recorded in the Banloc-Voiteg seismogenic structure (Romania) located on the southeastern border of the Pannonian Depression which is characterized by pre-Alpine and Alpine structures belonging to Tisa-Dacia Microplate and, particularly by the tectonic contact between two main geodynamic blocks. The seismic activity has a clear tendency to group on active neotectonic structures and displays different space and time patterns. Until now we have documented two major sequences (Imax=VIII EMS degree) in the study structure: October - November 1915 and July-December 1991. The 1991 sequence lasted several years, the seismic stations operated by NIEP recording thousands of aftershocks within several months. Some aftershocks had important macroseismic effects (e.g. 19.07.1991, Io=VII EMS). We refined hypocentral parameters for theis sequence using JHD relocation method. The new epicentres are well distributed in space and time defining two groups (phases) correlated with the faults systems in the study area. The focal mechanisms computed for the strongest events point out two orthogonal faults systems that were reactivated during the sequence, one oriented NE - SW (Banloc - Buzias Fault System) and the other one approximately E - W (Ittebej - Gataia Fault System) The seismic activity appears to migrate from South (Banloc phase, Mw=5.6, 12.07.1991) toward North (Voiteg phase, Mw=5.5, 02.12.1991) and further along Banloc - Buzias fault system.

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