Место издания: Florence , Год издания: 2004

We present seismic velocity models along two perpendicular seismic profiles with crosspoint 30 km to the south of the Mirny Kimberlite Pipe in Yakutia, Siberia. The data comprises recently digitized seismograms from vintage seismic sections that were acquired in 1981-1983 by use of Taiga analogue seismographs. The 370 km long, NW-striking profile I crosses the kimberlite pipe. It was covered by 41 seismographs. The perpendicular, 340 km long profile II was covered by 45 seismographs. The sources were 20 chemical shots along each profile, each loaded with between 1.5 and 6.0 ton of TNT distributed in individual charges of 100-200 kg in shallow water (<2 m deep). The data is of high quality with high signal/noise ratio to the furthest offsets. We have interpreted the data with seismic tomographic inversion of first arrivals and with 2D ray tracing, forward modelling. The velocity models show normal cratonic structure of the ca. 45 km thick crust with only slight undulation of the Moho. However, low velocity anomalies are detected to 25 km depth in the vicinity of the kimberlite pipe. Extremely high P-wave velocity (>8.7 km/s) of the sub-Moho mantle is interpreted along almost all of profile I, with a 80 km wide, low-velocity anomaly below the kimberlite. Profile II mainly shows Pn velocities of 8.0-8.2 km/s, with high velocity (>8.5 km/s) in two, ca. 100 km wide zones at its SW end. The nature of these exceptionally high, sub-Moho mantle velocities is not yet understood. The difference in velocity in the two profile directions indicate anisotropy, but the effect of unusual rock composition, e.g. from a high concentration of garnet, cannot be excluded.