Short-period QpP-P in Vrancea area - Romania
Marian Ivan*
* Dept. of Geophysics,
University of Bucharest, 6 Traian Vuia str., 70138 Bucharest 37, Romania.
e-mail: ivam@gg.unibuc.ro
(Received 18 November 2002; Accepted
17 February 2003)
Abstract: An investigation of P-wave attenuation in the northwestern part of the
Vrancea seismogenic body (Romania) is performed by using the two major seismic
events 1986 August 30th and 1990 May 30th, recorded by the
University of Utah Regional Network and Pacific Northwest Seismograph Network.
The results suggest both
horizontal and vertical QP variability, with values around 50 for
the upper mantle above 89 km and no dependence on frequency. For the upper
mantle above 137 km QP is around 90, with a possible frequency dependence. A decreasing of Q (increasing of
attenuation) from SW to NE is suggested along the north-western side of the
Vrancea seismogenic volume, above 89 km depth. It is a possible consequence of
a horizontal variation of the thermal field and / or of the tectonic stress in
the area.
Key words: P-wave attenuation, QP
factor, frequency dependence of attenuation, Vrancea (Romania) seismic region.