Premium
Separation of high‐frequency P N phases and mantle refracted P phases at distances between 6° and 18° in the western Pacific by ocean bottom seismograph array
Author(s) -
Ouchi Toru,
Nagumo Shozaburo,
Kasahara Junzo,
Koresawa Sadayuki
Publication year - 1983
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/gl010i011p01069
Subject(s) - mantle (geology) , seismometer , geology , seismology , ocean bottom , pacific ocean , geophysics , geodesy , oceanography
Observations of high‐frequency (HF) Pn phases by an oceanbottom seismometer (OBS) array were made at distances between 6° and 18° in the north‐western Pacific. At this distance range, mantle‐refracted P phases arrive earlier than HF‐Pn phases. These two phases are successfully separated for near surface earthquakes by applying appropriate filtering, since the dominant frequencies of HF‐Pn phases are higher than 6 Hz and the frequencies of mantle‐refracted P phases are rather low, about 3 Hz. The apparent velocities of HF‐Pn phases in this distance range are estimated to be from 8.3 to 8.1 km/sec or even lower, while those of mantle‐refracted P waves are from 8.4 to 8.6 km/sec. The reported value of 8.33 km/sec for Hf‐Pn phases appears to be an average of both HF‐Pn and mantle‐refracted P phases. Therefore, these observations suggest that a proposed additional HF‐Pn wave guide for the higher velocity of 8.33 km/sec is questionable.