## Resumé

Teleseismic *P*_{n} phases with a long, high-amplitude coda, are observed to offsets >3000 km along the Peaceful Nuclear Explosion seismic profiles Quartz and Ruby. For the high-frequency (>5 Hz) part of the Quartz data, which is shown here, coda lengths of more than 10 s can be visually observed in the seismic sections. We interpret the teleseismic *P*_{n} arrivals as multiple sub-Moho refractions (whispering-gallery phases), which travel over large distances due to a positive upper-mantle velocity gradient. The coda of these arrivals is explained by lower crustal scattering of the whispering-gallery phases from the mantle. The modelling is based on calculation of reflectivity and 2-D visco-elastic finite-difference synthetic seismograms. Our models are in agreement with other deep seismic data from continental areas, which typically show a reflective lower crust and an almost transparent uppermost mantle. The lower crustal heterogeneity is described by von Karman distribution with a standard deviation of 0.5 km s^{-1} for the P-wave velocity and correlation lengths of 2.4 km (horizontally) and 0.6 km (vertically). The positive vertical upper-mantle velocity gradient of ∼0.004 km s^{-1} km^{-1}, which is characteristic for profile Quartz, forms a waveguide which gives rise to the teleseismic P_{n}. It is not necessary to include upper-mantle heterogeneity in order to explain the characteristics of this arrival.

Originalsprog | Engelsk |
---|---|

Sider (fra-til) | F1-F7 |

Antal sider | 7 |

Tidsskrift | Geophysical Journal International |

Vol/bind | 152 |

Udgave nummer | 2 |

DOI | |

Status | Udgivet - feb. 2003 |

Udgivet eksternt | Ja |

## Programområde

- Programområde 3: Energiressourcer

## Fingeraftryk

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