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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 18:10 |
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Conference: Bucharest University Faculty of Physics 2009 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
Source parameters and directivity in the case of Vrancea intermediate-depth of 25th April 2009
Authors:
E. Popescu, M. Radulian, D. Ghica, M. Rogozea
Affiliation:
Institutul National de Cercetare Dezvoltare pentru Fizica Pamantului
E-mail
epopescu@infp.ro, mrogozea@inp.ro
Keywords:
Vrancea, Empirical Green’s function deconvolution, spectral ratios, source directivity
Abstract:
A moderate-size earthquake was recently generated in the Vrancea subcrustal domain, on April 25, 2009 (17:18, 45.68oN, 26.62oE, h=110 km, Mw = 5.6). It was the largest shock recorded since the event of October 27, 2004 (Mw = 6.0). The main shock was followed by a well-recorded aftershock on April 26, with similar location and focal mechanism (23:19, 45.69oN, 26.64oE, h=104 km, MW = 3.7). The difference of 1.9 magnitude units between the two shocks is typical for the aftershock activity in the Vrancea subcrustal domain, showing more efficient stress redistribution as compared with crustal events of similar size. The purpose of the present paper is to determine the seismic source parameters of the event of April 25, 2009 using the Empirical Green’s function deconvolution technique and spectral ratios. At the same time, the large number of high-quality waveforms recorded for the pair mainshock-aftershock provides an excellent database to investigate the possibility to detect source directivity properties. The source directivity effects are caused by the rupture propagation along a fault plane and manifest in different P pulse amplitude and width depending on the station position relative to the rupture fault plane. As shown by our study, noticeable directivity effects are pointed out even though the size of the event is moderate.
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