High-resolution measurement of the seismic attenuation across the Vrancea region, Romania

Abstract

We use teleseismic waveforms from a seismic refraction experiment along a N-S profile across the Vrancea region, Romania, to study seismic attenuation. This unique data set with an average station spacing of about 2-3 km provides spatial high-resolution estimates of the variability in seismic attenuation. Time windows of the analyzed seismic phases are extracted with a multiple-taper technique and spectral ratios (δt*) are determined. Our results from 4 teleseismic phases (P, pP, PKPdf, and PP) of two events underneath Hokkaido, Japan and New Guinea find a significant variation of the seismic attenuation along the line. A major influence of local site effects on the values of δt* can be excluded as well as a correlation with the Vrancea slab. The variations of the δt* operators from different phases at individual stations seem to be caused by the projection of three-dimensional attenuating structures at deep lithospheric levels. Copyright 2005 by the American Geophysical Union.