SEISMIC EVIDENCE FOR AN INNER-CORE TRANSITION ZONE

Citation
Xd. Song et Dv. Helmberger, SEISMIC EVIDENCE FOR AN INNER-CORE TRANSITION ZONE, Science, 282(5390), 1998, pp. 924-927
Citations number
34
Categorie Soggetti
Multidisciplinary Sciences
Journal title
ISSN journal
00368075
Volume
282
Issue
5390
Year of publication
1998
Pages
924 - 927
Database
ISI
SICI code
0036-8075(1998)282:5390<924:SEFAIT>2.0.ZU;2-Y
Abstract
Seismic waves that traverse Earth's inner core along north-south paths produce unusually broad pulse shapes at long periods (compared with w aves along east-west paths) and reflections from below;the inner core boundary at short periods. The observations provide compelling evidenc e for a seismic velocity discontinuity along north-south paths about 2 00 kilometers below the inner core boundary separating an isotropic up per inner core from an anisotropic Lower inner core. The triplication associated with such a structure might be responsible for reported wav eform complexity of short-period inner core arrivals along north-south paths and, if the depth of the boundary is laterally variable, their Large travel-time variation.