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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-21 20:53 |
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Conference: Bucharest University Faculty of Physics 2008 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
Seismic source characteristics and geodynamical features in the Vrancea region, Romania (POSTER)
Authors:
E. Popescu, A.O. Placinta, M. Popa, I. A. Moldovan and M. Radulian
Affiliation:
National Institute for Earth Physics, P.O.Box MG-2, Calugareni 12, Bucharest-Magurele, 077125, Romania
E-mail
anca@infp.ro
Keywords:
source parameters, empirical Green’s function, spectral ratio
Abstract:
The earthquakes clustered in a confined volume at intermediate depths beneath the Vrancea (Romania) seismic region are severely affecting an extended area of Romania and its neighboring countries. During the last century, five events with magnitudes larger than 6.5 occurred within this narrowly confined focal volume. A better understanding of the source process of Vrancea earthquakes is of crucial importance in order to properly assess the ground motion level that has to be expected from future large events and to model the geodynamics of this complex intra-continental convergence area. A substantial new amount of high-quality earthquake data have been recently gained through the progress of seismic networks on the Romanian territory within the cooperation programme with the University of Karlsruhe (Germany): Collaborative Research Centre 461 programme (Bonjer et al., 2000) and the tomography experiment CALIXTO’99 (Wenzel et al., 1999). On the basis of the new digital accelerometer and velocity data (Kinemetrics K2 and broadband instruments) we retrieve the source parameters of small-to-moderate earthquakes (2.9 ≤ MD ≤ 5.8) generated in the Vrancea subducting slab. Empirical Green’s function deconvolution and spectral ratio methods are applied for a set of 130 earthquakes. Pairs of collocated events with similar focal mechanism are selected in order to retrieve source parameters and to inspect the source scaling properties over the entire seismic active depth domain (60-180 km). Source parametrization and scaling are correlated with clustering properties of earthquake time, space and size distributions as well as with differences in specific source mechanisms or/and structural inhomogeneity properties along the subducting lithosphere. Our results confirm previous research focused on seismicity, tomography and seismic source scaling in the Vrancea region revealing significant subducting slab irregularity which was assumed to be in connection with differences in the physical, geochemical and tectonic processes at different scale lengths.
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