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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:22 |
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Conference: Bucharest University Faculty of Physics 2004 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
P-wave pulse analysis to retrieve source and propagation effects in the case of Vrancea earthquakes
Authors:
E. Popescu, M. Popa, A. Plãcintã, B. Grecu, M. Radulian
Affiliation:
National Institute for Earth Physics, P.O. Box MG-2, 077125, Bucharest, ROMANIA
E-mail
Keywords:
P-wave pulse,source, Vrancea earthquakes
Abstract:
Seismic source parameters and attenuation structure properties are obtained from the first P-wave pulse analysis and empirical Green’s function deconvolution. The P pulse characteristics are combined effects of source and path properties. To reproduce the real source and structure parameters it is crucial to apply a method able to distinguish between the different factors affecting the observed seismograms. For example the empirical Green’s function deconvolution method (Hartzell, 1978) allows the retrieve of the apparent source time function or source spectrum corrected for path, site and instrument effects. The apparent source duration is given by the width of the deconvolved source pulse and is directly related to the source dimension. Once the source time function established, next we can extract the parameters related to path effects. The difference between the pulse recorded at one station and the source pulse obtained by deconvolution is a measure of the attenuation along the path from focus to station. On the other hand, the pulse width variations with azimuths depend critically on the fault plane orientation and source directivity. In favourable circumstances (high signal/noise ratio, high resolution and station coverage), the method of analysis proposed in this paper allows the constraint of the rupture plane among the two nodal planes characterizing the fault plane solution, even for small events. P-wave pulse analysis is applied for 25 Vrancea earthquakes recorded between 1999 and 2003 by the Romanian local network to determine source parameters and attenuation properties. Our results outline high-stress drop seismic energy release with relatively simple rupture process for the considered events and strong lateral variation of attenuation of seismic waves across Carpathians Arc.
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