Seismic Evidence for an Inner Core Transition Zone
1998; American Association for the Advancement of Science; Volume: 282; Issue: 5390 Linguagem: Inglês
10.1126/science.282.5390.924
ISSN1095-9203
AutoresXiaodong Song, D. V. Helmberger,
Tópico(s)Geological and Geochemical Analysis
ResumoSeismic waves that traverse Earth's inner core along north-south paths produce unusually broad pulse shapes at long periods (compared with waves along east-west paths) and reflections from below the inner core boundary at short periods. The observations provide compelling evidence for a seismic velocity discontinuity along north-south paths about 200 kilometers below the inner core boundary separating an isotropic upper inner core from an anisotropic lower inner core. The triplication associated with such a structure might be responsible for reported waveform 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.
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