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In this paper the origin of precursors to P' P' with lead times greater than 50 s is investigated. Good NORSAR records of P'650P' and P'400P' for these arrivals as well as corresponding slowness estimates are presented. These phases are interpreted as done by others in terms of underside reflections from discontinuities or sharp transition zones in the upper mantle. An extensive search of 5 years of NORSAR records did not produce any significant evidence on P' P' precursor arrivals with lead times greater than 50 s other than those mentioned above.
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