A new Moho boundary map for the northern Fennoscandian Shield based on combined controlled-source seismic and receiver function data

Abstract

We present a new Moho map for the Early-Proterozoic northwestern part of the Fennoscandian Shield, where the POLENET/LAPNET passive seismic array was located. The map is based on previously published and re-evaluated controlled source seismic data and P-wave receiver functions as well as new estimates of the Moho depth obtained by our analysis of P-wave receiver functions at broadband stations of the POLENET/LAPNET array. We estimated individual data quality for all input data and combined them into a new Moho map using CRUST3D software. The software seeks the simplest (smoothest) Moho surface that is consistent with all seismic data within their individual uncertainty limits. The new Moho map indicates that the crustal thickness in the study region varies between 42 km and 58 km, with the greatest thickness being reached in two separate areas in the northeast and the southeast. Two areas with relatively flat and shallow Moho, with an average Moho depth of c. 44 km, are located in the eastern and south-western parts of the study area. These two areas are separated by the Moho depression, with a maximum depth of 58 km. They can be associated with the Archean core of the Karelian craton and with the part of it that was reworked during the Early Proterozoic, respectively. A region with an average Moho depth of c. 47 km can be seen in the northern part of our study area, deepening to c. 55 km in the northeastern corner.