Seismic 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.
|Original language||English (US)|
|Number of pages||4|
|State||Published - Oct 30 1998|
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