Crustal structure of the Baltic Shield beneath Umeå, Sweden, from the spectral behavior of long-period P waves

Abstract

abstract The method of spectral ratio response for crustal thickness determination beneath a receiving station, using long-period P waves of teleseismic events, has been applied. The purpose of this study is to investigate further the already well-depicted shield structure in Sweden beneath the WWSSN station at Umeå, the methodical procedure involved in this inversion problem, and possible sensitivity of the method to lateral variations of the shield area beneath the recording station. Teleseismic events from the Okhotsk Sea, Mongolia, and Hindu Kush regions are considered. Results suggest a value of 42 km for the two-layer crustal model beneath Umeå with possible lateral variations in velocity and/or dipping M-discontinuity surface to the east. It is proposed that a quantitative measure of the reliability of amplitudes and periodicity of peaks of the response ratios and indications of possible lateral anisotropy are obtained by treating the horizontal P-wave component both as a radial component of a three-component vector field and as being along the great circle through the epicenter and the receiving station.