P-wave mantle velocity structure beneath northern Eurasia from long-range recordings along the profile Quartz

摘要: High-resolution seismic sounding of the mantle using two Peaceful Nuclear Explosions (PNEs) along 3950 km long Quartz profile in northern Eurasia reveal major unexpected vertical and lateral inhomogeneities. In contrast to standard seismological earth models such as PREM IASP91 three, rather than two, discontinuities are found between 400 700 depth. They located at about 420, 550 670 Lateral variations depths amount 10–20 km, associated P-wave velocities vary by 0.1 s−1. upper mantle, uppermost layer through which Pn propagates extends down 100 The below this depth, but above 410 discontinuity, is characterized alternating high low depth range 200 km. velocity fluctuates 8.3 8.7 s−1 shows from shotpoint shotpoint. Average clearly higher reference models. This part overlies a low-velocity zone 300 channel also displays substantial variation could be interpreted laterally variable asthenosphere. Beneath West Siberian basin asthenosphere seems well established whereas it only poorly defined under Uralian belt tectonic units northwest. With addition more data other profiles, future aims include two-dimensional three-dimensional tomographic modelling, modelling petrological composition, 850 beneath Eurasia.