UPPERMOST INNER CORE ATTENUATION FROM PKP DATA OBSERVED AT SOME SOUTH AMERICAN SEISMOLOGICAL STATIONS

Abstract

QP factor at the top of the inner core (IC) is derived using the amplitude spectral ratio (PKPbc versus PKPdf) method applied to the waveforms of suitable, strong (magnitude > 6.0) intermediate depth and deep (h > 150 km) earthquakes recorded at some selected South American stations. In most cases, the sampled volume of the IC is centred beneath the Pacific Ocean, but some QP values correspond to volumes under South Africa and under Northern Atlantic. The obtained value of QP is 323 ± 16 (at 95 per cent confidence level), close to a normal (Gaussian) distribution. The maximum depth of penetration of the PKPdf phase into the IC is roughly 333 km, suggesting a possible increase of QP with depth, although the large scatter in data prevents a definite conclusion. As regards the geographical patterns no variation was observed. © 2006 The Authors Journal compilation © 2006 RAS.