Short-period QpP-P in Vrancea area - Romania



Marian Ivan*


* Dept. of Geophysics, University of Bucharest, 6 Traian Vuia str., 70138 Bucharest 37, Romania.



(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.