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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 18:32 |
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Conference: Bucharest University Faculty of Physics 2016 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
Spatial patterns of the peak ground acceleration displayed by the Vrancea undercrustal earthquakes
Authors:
Cristian GHITA, Luminita ARDELEANU, Bogdan GRECU, Cristian NEAGOE
Affiliation:
National Institute for Earth Physics, Magurele, Ilfov, Romania
E-mail
cristi.ghita@infp.ro
Keywords:
Vrancea region, subcrustal earthquakes, peak ground acceleration
Abstract:
The level of the seismic ground motion at a particular site are determined by several factors: the characteristics of the seismic source (earthquake size, focal depth, focal mechanism, peculiarities of the rupture process), the seismic wave propagation from the source to the site (hypocentral/epicentral distance, physical properties of the medium along the ray path), and the local site effects (local geology.Vrancea region, the most dangerous seismogenic zone in Romania, is located at the bending of the Eastern Carpathians, in the depth range 60 - 200 km. The patterns of the ground motions generated by the strong undercrustal earthquakes of Vrancea exhibit a couple of common features, which indicate that the level of ground shaking is strongly controlled by the local and regional geological conditions: (i) large values of ground motion parameters observed over wide areas orientated predominantly NE-SW; (ii) strong, abnormal attenuation of the seismic waves propagating towards the Intra-Carpathian zone.
The large amount of recently collected high quality data allowed us to examine the spatial distributions of the peak ground accelerations generated by several tens of moderate-size events (magnitude Mw ≥ 4.0) which occurred during the past decade.The observed spatial patterns display the common features emphasized by the strong events, indicating that the local and regional geological conditions control the ground shaking to a larger degree than the focal distance. On the other hand, the individual patterns exhibit a notable variability, consequence of the diversity of the focal mechanisms and hypocenter locations within the seismogenic zone. The contributions of these two factors to the spatial pattern variability cannot be quantified separately, they are combined in a particular way for each event; the analysis shows that even rather small variability in source mechanism and source location may result in noticeable differences of the observed ground motion distributions.
Acknowledgement:
The research was supported by the National Authority for Scientific Research and Innovation of Romania, Nucleu Program, project PN 16 35 01 02.
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