a b s t r a c tTectonics and erosion are the driving forces in the evolution of mountain belts, but the identification of their relative contributions remains a fundamental scientific problem in relation to the understanding of both geodynamic processes and surface processes. The issue is further complicated through the roles of climate and climatic change. For more than a century it has been thought that the present high topography of western Scandinavia was created by some form of active tectonic uplift during the Cenozoic. This has been based mainly on the occurrence of surface remnants and accordant summits at high elevation believed to have been graded to sea level, the inference of increasing erosion rates toward the present-day based on the age of offshore erosion products and the erosion histories inferred from apatite fission track data, and on over-burial and seaward tilting of coast-proximal sediments.In contrast to this received wisdom, we demonstrate here that the evidence can be substantially explained by a model of protracted exhumation of topography since the Caledonide Orogeny. Exhumation occurred by gravitational collapse, continental rifting and erosion. Initially, tectonic exhumation dominated, although erosion rates were high. The subsequent demise of onshore tectonic activity allowed slow erosion to become the dominating exhumation agent. The elevation limiting and landscape shaping activities of wet-based alpine glaciers, cirques and periglacial processes gained importance with the greenhouse-icehouse climatic deterioration at the Eocene-Oligocene boundary and erosion rates increased. The flattish surfaces that these processes can produce suggest an alternative to the traditional tectonic interpretation of these landscape elements in western Scandinavia. The longevity of western Scandinavian topography is due to the failure of rifting processes in destroying the topography entirely, and to the buoyant upward feeding of replacement crustal material commensurate with exhumation unloading.We emphasize the importance of differentiating the morphological, sedimentological and structural signatures of recent active tectonics from the effects of long-term exhumation and isostatic rebound in understanding the evolution of similar elevated regions.

S U M M A R YWe present a novel method to recover absolute S velocities from receiver functions.For a homogeneous half-space the S velocity can be calculated from the horizontal slowness and the angle of surface particle motion for an incident P wave. Generally, the calculated S velocity is an apparent half-space value which depends on model inhomogeneity and P-waveform. We therefore, suggest to calculate such apparent half-space S velocities from low-pass filtered (smoothed) receiver functions using a suite of filter-parameters, T. The use of receiver functions neutralize the influence of the P-waveform, and the successive low-pass filterings emphasize the variation of S velocity with depth.We apply this V S,app. (T ) technique to teleseismic data from three stations: FUR, BFO and SUM, situated on thick sediments, bedrock and the Greenland ice cap, respectively. The observed V S,app. (T ) curves indicate the absolute S velocities from the near surface to the uppermost mantle beneath each station, clearly revealing the different geological environments. Application of linearized, iterative inversion quantify these observations into V S (z) models, practically independent of the S-velocity starting model. The obtained models show high consistency with independent geoscientific results. These cases provide also a general validation of the V S,app. (T ) method.We propose the computation of V S,app. (T ) curves for individual three-component broad-band stations, both for direct indication of the S velocities and for inverse modelling.In applied receiver function analysis it is often stated that receiver functions are not sensitive to the absolute levels of the S velocity (e.g. Ammon et al. 1990;Kind et al. 1995;Schlindwein 2006;Tomlinson et al. 2006). In the present paper, we show that this is not entirely correct. We present a simple transform which clearly emphasizes the absolute S-velocity information present in receiver functions. The effect of the free surface on an incoming teleseismic P wave plays a key role in this method.A plane P wave incident on a free surface is reflected as a P wave and a converted SV wave. The particle motion (or polarization) observed by a three-component seismograph on this surface is the superposition of the incoming and the two outgoing waves. As a result the apparent incidence angle (i P ) defined by the surface particle motion is different from the true P wave incidence angle (i P ). The relation between true and apparent incidence angles was early quantified in Wiechert (1907, eq. 128) (see also e.g. Nuttli & Whitmore 1961) from which followswhere V P and V S are compressional and shear velocities of the half-space and p the horizontal slowness (ray parameter) of the P wave. Eq. (1) can be rearranged towhich defines the half-space S velocity as a function of the observed apparent incidence angle and slowness of a P wave. No assumptions are made concerning V P or V P /V S . Bostock & Rondenay (1999) derived an equivalent but less simple expression (their eq. A6) from the free-surf...

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.

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[1] Reading et al. [2003] propose a transformation which takes the rectangular coordinate system ZRT to the 'skew' PSH system. The transformation isolates P-, SV-and SH-waves of same slowness on the P-, S-and H-component, respectively, and removes the free surface effect. We have the following comments to their article: A) The transformation matrix in their paragraph has misprints propagated to the text in their Figure 1c. B) The LQT rotation [Vinnik, 1977] has no leakage of P-displacement into the Q-component, although a minor SV-leakage is present on the L-component. C) The differences between PSH-and ZRT-receiver functions are large, whereas the differences between PSH-and LQT-receiver functions are very small in theory and hardly ever significant in practice. Jacobsen (2004), Comment on ''Improved inversion for seismic structure using transformed, S-wavevector receiver functions: Removing the effect of the free surface'' by Anya Reading, Brian Kennett, and Malcolm Sambridge, Geophys.