POLENET/LAPNET teleseismic P-wave traveltime tomography model of the upper mantle beneath northern Fennoscandia
Abstract. The POLENET/LAPNET broadband seismic array was deployed in northern Fennoscandia (Finland, Sweden, Norway, and Russia) during the third International Polar Year 2007–2009. The array consisted of roughly 60 seismic stations. In our study we estimate the 3-D architecture of the upper mantle beneath the northern Fennoscandian shield using high-resolution teleseismic P-wave tomography. For this purpose 111 clearly recorded teleseismic events were selected and the data from the stations handpicked and analysed. Our study reveals a highly heterogeneous lithospheric mantle beneath the northern Fennoscandian shield though without any large high P-wave velocity area that may indicate presence of thick depleted lithospheric "keel". The most significant feature seen in the velocity model is a large elongated negative velocity anomaly (up to −3.5 %) in depth range 100–150 km in the central part of our study area that can be followed down to a depth of 200 km in some local areas. This low-velocity area separates three high-velocity regions corresponding to the cratons and it extends to greater depth below the Karelian craton.