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High‐frequency waves following PKP‐C DIFF at distances greater than 155°
Author(s) -
Nakanishi Ichiro
Publication year - 1990
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl017i005p00639
Subject(s) - geology , slowness , amplitude , seismology , scattering , geodesy , seismic wave , oscillation (cell signaling) , geophysics , physics , optics , biology , genetics
Using a seismic network in Hokkaido‐Tohoku region, Japan we observe PKP waves in the distance range 152 to 157°from a deep earthquake in Argentina. The seismic network consists of 26 stations and provides us with a data set of dense distance sampling. The examination of amplitude variation of PKP‐BC and PKP‐C diff with distance locates the C‐cusp at about 155.5° for a surface source for the path from Argentina to Japan. This C‐cusp position suggests a P velocity of 10.27 km/s at the bottom of the outer core. The bandpass filtering of the data shows that high‐frequency waves are observed following PKP‐C diff at distances beyond the C‐cusp. The waves are characterized by a dominant frequency of about 2 to 3 Hz, a long duration of oscillation until the arrival of PKP‐AB, and an apparent onset slowness of about 4 s/deg, which is approximately equal to that of PKP‐AB in the distance range. The onset time of the high‐frequency waves seems to be consistent with the least time of the scattering of PKP‐BC on the receiver side near the bottom of the upper mantle.