Revisit of the Fennoscandian Shield along the UPPLAND seismic profile: competitive velocity models
<p>This paper presents a comprehensive re-analysis of seismic data collected along the UPPLAND profile in the Fennoscandian Shield, focusing on the competitive velocity models for P-wave (<span class="inline-formula"><i>V</i><sub>p</sub></span>) an...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-07-01
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| Series: | Solid Earth |
| Online Access: | https://se.copernicus.org/articles/16/727/2025/se-16-727-2025.pdf |
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| Summary: | <p>This paper presents a comprehensive re-analysis of seismic data collected along the UPPLAND profile in the Fennoscandian Shield, focusing on the competitive velocity models for P-wave (<span class="inline-formula"><i>V</i><sub>p</sub></span>) and S-wave (<span class="inline-formula"><i>V</i><sub>s</sub></span>) velocities and the <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>V</mi><mi mathvariant="normal">p</mi></msub><mo>/</mo><msub><mi>V</mi><mi mathvariant="normal">s</mi></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="28pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="5c51f93780cc45ae0983a9094a76fffa"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="se-16-727-2025-ie00001.svg" width="28pt" height="16pt" src="se-16-727-2025-ie00001.png"/></svg:svg></span></span> ratio. The initial data collection was conducted in 2017, and the first interpretation was published by Buntin et al. (2021). This study reveals that, while both the previous and current models exhibit similar velocities up to a depth of approximately 35 km, significant discrepancies arise in the lower-crust and upper-mantle velocities and in the depth of the Moho boundary. The preferred model obtained by 2D forward ray-tracing modelling indicates <span class="inline-formula"><i>V</i><sub>p</sub></span> values of approximately 7.05–7.17 km s<span class="inline-formula"><sup>−1</sup></span> in the lower crust (LC) and 8.05 km s<span class="inline-formula"><sup>−1</sup></span> in the upper mantle (UM), contrasting with the earlier model's values of 7.25–7.4 and 8.0–8.5 km s<span class="inline-formula"><sup>−1</sup></span>, respectively. The Moho depth varies between 43–50 km in the new model, compared to 45–52 km in the previous one.</p>
<p>In addition, we present two, possibly overlapping, tectonic interpretations to explain the new model. The main crustal structure formed during W-vergent crustal stacking at ca. 1.86 Ga, followed by N–S crustal shortening at 1.82–1.80 Ga. The bulging of the high-velocity upper mantle is either related to extension at 1.89–1.87 Ga in a continental back-arc or was formed during extensional magmatism at 1.6/1.7/1.8 Ga. The findings highlight the complexities in determining lower-crustal and upper-mantle properties from ambiguous seismic data and suggest that the interpretations presented may require a more cautious approach, allowing alternative explanations.</p> |
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| ISSN: | 1869-9510 1869-9529 |