The Propagation of Pn
A propagation model for the oceanic Pn phase is presented in which the onset consists of a refraction from the lower oceanic lithosphere while the subsequent coda is a result of near-receiver sediment and water reverberation. The first arrival of the oceanic Pn phase remains entirely within the lithosphere and for epicentral ranges in excess of 25° to 30° contains a free surface reflection, similar to the seismic phase PP. At large epicentral distances, or similarly for deep events, the Pn wavetrain is preceded by a low frequency forerunner which has traversed the low Q asthenosphere. The coda of the Pn phase was analyzed through the computation of synthetic seismograms using wavenumber integration. Spectral characteristics associated with both sediment and water reverberation are clearly observed in both the synthetics and data collected in the southwest Pacific during the 1983 Ngendei Seismic Experiment.
KeywordsGroup Velocity Synthetic Seismogram Instrument Response Synthetic Spectrum Ocean Bottom Seismometer
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