Crustal root beneath the highlands of southern Norway resolved by teleseismic receiver functions

Abstract

SUMMARY Teleseismic data have been collected with temporary seismograph stations on two profiles in southern Norway. Including the permanent arrays NORSAR and Hagfors the profiles are 400 and 500 km long and extend from the Atlantic coast across regions of high topography and the Oslo Rift. A total of 1071 teleseismic waveforms recorded by 24 temporary and 8 permanent stations are analysed. The depth‐migrated receiver functions show a well‐resolved Moho for both profiles with Moho depths that are generally accurate within ±2 km. For the northern profile across Jotunheimen we obtain Moho depths between 32 and 43 km (below sea level). On the southern profile across Hardangervidda, the Moho depths range from 29 km at the Atlantic coast to 41 km below the highland plateau. Generally the depth of Moho is close to or above 40 km beneath areas of high mean topography (>1 km), whereas in the Oslo Rift the crust locally thins down to 32 km. At the east end of the profiles we observe a deepening Moho beneath low topography. Beneath the highlands the obtained Moho depths are 4–5 km deeper than previous estimates. Our results are supported by the fact that west of the Oslo Rift a deep Moho correlates very well with low Bouguer gravity which also correlates well with high mean topography. The presented results reveal a ca. 10–12 km thick Airy‐type crustal root beneath the highlands of southern Norway, which leaves little room for additional buoyancy‐effects below Moho. These observations do not seem consistent with the mechanisms of substantial buoyancy presently suggested to explain a significant Cenozoic uplift widely believed to be the cause of the high topography in present‐day southern Norway.

Deep structure of the northern North Sea and southwestern Norway based on 3D density and magnetic modelling

“…3C) by Stratford et al (2009) and have been used as additional input data for 3D density modelling, also with partial use of data from Maystrenko & ScheckWenderoth (2013). The refraction seismic results of Stratford et al (2009) are also generally consistent with the previous receiver function results by Svenningsen et al (2007) and can therefore be considered as reliable high-quality data for Moho depth beneath SW Norway. The lithosphere-asthenosphere boundary has been derived from previously published data, such as the seis-8C).…”

“…In contrast, the regional crustal structure of the northern North Sea and the adjacent continent is less well known compared with the sedimentary level. Our knowledge of the structure of the crystalline crust within the study area is mainly based on 2D deep reflection and refraction seismic lines (Calcagnile, 1982;Christie, 1982;Barton & Wood, 1984;Klemperer & White, 1989;Iwasaki et al, 1994;McBride & England, 1999;Abramovitz & Thybo, 2000;Christiansson et al, 2000;Nielsen et al, 2000;Erickson, 2004;Sandrin & Thybo, 2008;Sandrin et al, 2009;Stratford et al, 2009;Stratford & Thybo, 2011;Thybo & Nielsen, 2012;Kvarven et al, 2014Kvarven et al, , 2016 and teleseismic receiver functions (Ottemöller & Midzi, 2003;Svenningsen et al, 2007). Furthermore, several potential field studies have revealed additional important features of the deep structure within the study area both in 2D (Åm, 1973;Hovland, 1987;Olesen et al, 2004;Lyngsie et al, 2006;Fichler et al, 2011;Ebbing et al, 2012;Kvarven et al, 2014;Nirrengarten et al, 2014 and others) and in 3D (Tesauro et al, 2007;Yegorova et al, 2007;Kaban et al, 2010;).…”

Upper-mantleP- andS-wave velocities across the Northern Tornquist Zone from traveltime tomography

“…From previous studies on crustal thickness and gravity data (e.g. Balling 1980;Svenningsen et al 2007;Ebbing et al 2012), we find that the high topography of the Southern Scandes Mountains is isostatically compensated mainly by a thickened crust, thought to be largely of Caledonian age, resulting from continentcontinent collision between Baltica and Laurentia (cf. introduction and Nielsen et al 2009).…”

“…Crustal velocity and thickness are mainly determined by seismic refraction experiments and by analyses of receiver functions (EUGENO-S Working Group 1988; Iwasaki et al 1994;Svenningsen et al 2007;Olsson et al 2008;Sandrin & Thybo 2008;Stratford et al 2009;Stratford & Thybo 2011;. For a recent compilation and analysis, see Artemieva & Thybo (2013).…”

Mantle roots of the Emeishan plume: an evaluation based on teleseismic P-wave tomography

“…It has been shown that in some cases, high-and lowvelocity relics generated by subducted slab or crustal and mantle lithospheric delamination resulting in the upwelling of the asthenospheric mantle can be retained for a long time, even a couple of billion years (Cook et al, 1999;Balling, 2000;Svenningsen et al, 2007;Zhai et al, 2007;He et al, 2015). These low-and high-velocity structures can be imaged by tomography (Zhao et al, 1992(Zhao et al, , 1994Zhao et al, 2016).…”