Seismic structure near the inner core-outer core boundary
Article first published online: 7 DEC 2012
Copyright 1994 by the American Geophysical Union.
Geophysical Research Letters
Volume 21, Issue 2, pages 157–160, 15 January 1994
How to Cite
- Issue published online: 7 DEC 2012
- Article first published online: 7 DEC 2012
- Manuscript Accepted: 18 NOV 1993
- Manuscript Received: 28 JUL 1993
A model of P-wave velocity of the Earth's core 500 km above and below the inner core boundary (ICB) beneath North America is constructed from travel time analysis and broad-band waveform modeling of core phases at distances from 130° to 160°. Differential travel times between PKPBC (Cdiff) and PKPDF (TBC–TDF) are about 0.5 sec shorter than those computed from PREM at distances from 146° to 152° and increase with distance to nearly the same as those from PREM at 155°. Differential travel times between PKPCD and PKPDF (TCD–TDF) at distances from 130° to 143° are approximately 0.2 sec shorter than those of PREM. Amplitudes of PKPBC (Cdiff) relative to PKPDF (ABC/ADF) at distances 150° to 156° are about 40% larger than those from PREM. These observations require a smaller P-wave velocity gradient (0.0005 sec−1) in the lowermost 300 km of the outer core than that from PREM (∼0.00065 sec−1), a slower P-wave velocity (10.96 km/sec) at the top of the inner core, and a larger velocity gradient (0.0005 sec−1) in the uppermost 300 km of the inner core.