DBPapers
DOI: 10.5593/SGEM2015/B13/S5.112

FOCAL MECHANISM ANALYSIS FOR THE SEISMIC SWARM RECORDED IN GALATI AREA (ROMANIA) BETWEEN SEPTEMBER –NOVEMBER 2013

A. Craiu, A. Marmureanu, M. Diaconescu, M. Craiu, C. Ionescu
Friday 7 August 2015 by Libadmin2015

References: 15th International Multidisciplinary Scientific GeoConference SGEM 2015, www.sgem.org, SGEM2015 Conference Proceedings, ISBN 978-619-7105-33-9 / ISSN 1314-2704, June 18-24, 2015, Book1 Vol. 3, 863-870 pp

ABSTRACT
In this paper we present the results obtained during the study of swarm of earthquake close to the Galati city. In the last period the National Seismic Network was continuously upgraded, which allows presently to easily detect earthquakes with very low magnitudes in every seismic region of Romania.
The seismogenic region of the swarm is situated between two main crustal faults, oriented SE-NW: Sf. Gheorghe fault (located in North Dobrogea, in the Scythian Platform) to the North, and Peceneaga Camena fault (which separates North Dobrogea block from the Moesian Platform) to the South. The epicentral zone belongs to a complex tectonic area, in which a secondary fault system – lying NE-SW, perpendicular to the dominant system – is present too.
The seismic swarm started on September 23, 2013, close to Galati city, in Izvoarele region (Romania), and lasted until November 12, 2013. 406 earthquakes were recorded during several phases of seismic activity. The strongest events – a magnitude 3.9 earthquake, occurred on September 29, and two ML 3.8 shocks, occurred on October 3 and October 4, respectively, were accompanied by specific seismicity bursts.
The spatial distribution of the epicenters, which are aligned in NE-SW direction, indicates that the seismic swarm was generated by the second fault system. The focal mechanisms show normal slip, with one of the nodal planes oriented roughly in NE-SW direction.
The results are discussed and interpreted in relation with the regional seismotectonics, our study aiming to emphasize new elements and implications for seismic hazard evaluation in the Galati area.

Keywords: seismic swarm, focal mechanism