Crustal structure and intraplate seismicity in Nordland, Northern Norway: insight from seismic tomography
SUMMARY The Nordland region, Northern Norway, situated in an intraplate continental setting, has the highest seismicity rate in mainland Norway. However, the exact cause of seismicity in this region is still debated. Better understanding of factors that influence the seismicity in Nordland can help...
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croxfordunivpr:10.1093/gji/ggac086 2024-09-15T18:20:32+00:00 Crustal structure and intraplate seismicity in Nordland, Northern Norway: insight from seismic tomography Shiddiqi, H A Ottemöller, L Rondenay, S Halpaap, F Gradmann, S Michálek, J Research Council of Norway 2022 http://dx.doi.org/10.1093/gji/ggac086 https://academic.oup.com/gji/advance-article-pdf/doi/10.1093/gji/ggac086/42619317/ggac086.pdf https://academic.oup.com/gji/article-pdf/230/2/813/43373196/ggac086.pdf en eng Oxford University Press (OUP) https://creativecommons.org/licenses/by/4.0/ Geophysical Journal International volume 230, issue 2, page 813-830 ISSN 0956-540X 1365-246X journal-article 2022 croxfordunivpr https://doi.org/10.1093/gji/ggac086 2024-07-29T04:22:47Z SUMMARY The Nordland region, Northern Norway, situated in an intraplate continental setting, has the highest seismicity rate in mainland Norway. However, the exact cause of seismicity in this region is still debated. Better understanding of factors that influence the seismicity in Nordland can help increase knowledge of intraplate seismicity in general. Here, we address this problem with the aid of a new high-resolution 3-D VP and VP/VS ratio images of the crust in Nordland using seismic traveltime tomography. These images show the existence of a localized, 10–15 km Moho step that runs parallel to the coast. The north–south extent of this step coincides with the region that exhibits the highest rates of seismicity. Focal mechanisms of selected earthquakes computed in this study are dominated by normal and oblique-normal, indicating a coast-perpendicular extension. The coast-perpendicular extensional stress regime deviates from the regional compression imposed by the ridge push from the North Atlantic. This deviation is thought to stem from the additional interference with local flexural stress caused by sediment redistribution and glacial isostatic adjustment, and possibly exacerbated by gravitational potential energy stress associated with the Moho step. The deformation due to the extensional regime is localized on pre-existing faults and fractures along the coastline. The tomography result shows that two distinct seismic swarms occurred in the coastal area with low VP and variable VP/VS ratio anomalies, pointing towards fractured crust and possibly the presence of fluids. The existence of fluids here can change the differential stress and promote seismic rupture. Article in Journal/Newspaper Nordland Nordland North Atlantic Northern Norway Nordland Oxford University Press Geophysical Journal International |
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Open Polar |
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Oxford University Press |
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croxfordunivpr |
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English |
description |
SUMMARY The Nordland region, Northern Norway, situated in an intraplate continental setting, has the highest seismicity rate in mainland Norway. However, the exact cause of seismicity in this region is still debated. Better understanding of factors that influence the seismicity in Nordland can help increase knowledge of intraplate seismicity in general. Here, we address this problem with the aid of a new high-resolution 3-D VP and VP/VS ratio images of the crust in Nordland using seismic traveltime tomography. These images show the existence of a localized, 10–15 km Moho step that runs parallel to the coast. The north–south extent of this step coincides with the region that exhibits the highest rates of seismicity. Focal mechanisms of selected earthquakes computed in this study are dominated by normal and oblique-normal, indicating a coast-perpendicular extension. The coast-perpendicular extensional stress regime deviates from the regional compression imposed by the ridge push from the North Atlantic. This deviation is thought to stem from the additional interference with local flexural stress caused by sediment redistribution and glacial isostatic adjustment, and possibly exacerbated by gravitational potential energy stress associated with the Moho step. The deformation due to the extensional regime is localized on pre-existing faults and fractures along the coastline. The tomography result shows that two distinct seismic swarms occurred in the coastal area with low VP and variable VP/VS ratio anomalies, pointing towards fractured crust and possibly the presence of fluids. The existence of fluids here can change the differential stress and promote seismic rupture. |
author2 |
Research Council of Norway |
format |
Article in Journal/Newspaper |
author |
Shiddiqi, H A Ottemöller, L Rondenay, S Halpaap, F Gradmann, S Michálek, J |
spellingShingle |
Shiddiqi, H A Ottemöller, L Rondenay, S Halpaap, F Gradmann, S Michálek, J Crustal structure and intraplate seismicity in Nordland, Northern Norway: insight from seismic tomography |
author_facet |
Shiddiqi, H A Ottemöller, L Rondenay, S Halpaap, F Gradmann, S Michálek, J |
author_sort |
Shiddiqi, H A |
title |
Crustal structure and intraplate seismicity in Nordland, Northern Norway: insight from seismic tomography |
title_short |
Crustal structure and intraplate seismicity in Nordland, Northern Norway: insight from seismic tomography |
title_full |
Crustal structure and intraplate seismicity in Nordland, Northern Norway: insight from seismic tomography |
title_fullStr |
Crustal structure and intraplate seismicity in Nordland, Northern Norway: insight from seismic tomography |
title_full_unstemmed |
Crustal structure and intraplate seismicity in Nordland, Northern Norway: insight from seismic tomography |
title_sort |
crustal structure and intraplate seismicity in nordland, northern norway: insight from seismic tomography |
publisher |
Oxford University Press (OUP) |
publishDate |
2022 |
url |
http://dx.doi.org/10.1093/gji/ggac086 https://academic.oup.com/gji/advance-article-pdf/doi/10.1093/gji/ggac086/42619317/ggac086.pdf https://academic.oup.com/gji/article-pdf/230/2/813/43373196/ggac086.pdf |
genre |
Nordland Nordland North Atlantic Northern Norway Nordland |
genre_facet |
Nordland Nordland North Atlantic Northern Norway Nordland |
op_source |
Geophysical Journal International volume 230, issue 2, page 813-830 ISSN 0956-540X 1365-246X |
op_rights |
https://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.1093/gji/ggac086 |
container_title |
Geophysical Journal International |
_version_ |
1810458915189555200 |