Open AccessCore Phases and the Inner Core Boundary
Author(s) -
Subiza Gonzalo Payo,
Båth Markus
Publication year - 1964
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1964.tb06304.x
Subject(s) - amplitude , inner core , core (optical fiber) , phase (matter) , geology , geodesy , layering , period (music) , transition zone , boundary (topology) , geometry , seismology , optics , physics , mathematics , geophysics , mathematical analysis , botany , quantum mechanics , acoustics , biology
Summary A study is made of waves of short period and small amplitude arriving before and after P in the interval of 120°‐155° by using 215 readings of 53 earthquakes as recorded by the Swedish seismological network from 1951 to 1962. Travel‐time curves are determined for two phases P O and P 1 preceding P up to 10–15 s and 6 s, respectively, also for P itself, as well as for another phase P L , following P after 1.5 ‐ 4s. The average periods of the waves P O , P 1 , P and P L are 0.66, 0.76, 0.88 and 2.32 s, respectively. The amplitude/period ratios for the sequence P O :P 1 :P:P L , expressed in mμ/s with its value for P normalized to 100, are 27:41:100:551. The periods are independent of distance, focal depth and magnitude, whereas the amplitude/period ratios exhibit some variations with distance. The results are discussed in connection with wave propagation through the transition zone between the outer and inner core. Even if definite conclusions cannot be reached, there is fairly good indication that this transition zone is more complicated in its structure than generally assumed hitherto and possibly has an internal layering. The study also reports observations of PP, especially cases with double onsets. These are found to correspond mainly to P 1 and P 2 travelling over the greater arc.