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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:13 |
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Conference: Bucharest University Faculty of Physics 2013 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
Source parameters for the December 2011 – January 2012 seismic sequence in the Southern Carpathians, Romania
Authors:
Mircea Radulian, Emilia Popescu, Felix Borleanu, M. DIACONESCU
Affiliation:
National Institute for Earth Physics, 12 Calugareni str., 077125, Magurele, Ilfov
E-mail
mircea@infp.ro
Keywords:
seismic source, earthquake sequence, empirical Green`s function, source scaling
Abstract:
The goal of the paper is to investigate the most recent crustal earthquake sequence (40 earthquakes detected and located in the time interval 30 December 2011– 10 January 2012), occurred in the weastern part of the Getic Depression (about 20 km east from the Tg-Jiu city). The largest shock was produced on January 1, 2012, 23:57 (h=14 km, MD = 4.5), preceded by 7 foreshocks (MD less than 3.6) within 65-hour interval. The following greatest shocks of magnitude 4.0 and 3.9 occurred within the first 30-minute interval. Seismic source properties are determined using empirical Green’s function (EGF) deconvolution and spectral ratios technique. These approaches require co-located events associated with the main events (MD = 4.5, 4.0, 3.9), selected according to the requirements for empirical Green’s functions. The source parameters are estimated as mean values for all the available pairs. Our analysis reveals distinct features, such as the alignment of the foreshocks and aftershocks along a NW-SE direction, in agreement with the focal mechanism similar for the three largest events, showing a rupture plane in the same direction. The relative location of the main shock indicates a unilateral rupture, from SE toward NW. In parallel, source parameters are retrieved and scaling relations are estimated. The resulted source time functions are similar from one station to the other, suggesting negligible source directivity effects for the study events. The shape of the deconvolved source time function for the main shock of 1 January 2012 indicates a homogeneous rupture process in the focus. The scaling relationships for the estimated source parameters are compatible with scaling relationships characteristic for other seismic regions in the world. Also they fall well within the scaling range determined for the crustal sequences located in the eastern part of the South Carpathians region.
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