Glacial isostatic adjustment strain rate – stress paradox in the Western Alps, impact on active faults and seismicity
In many regions formerly glaciated during the Last Glacial Maximum (LGM), glacial isostatic adjustment (GIA) explains most of the measured uplift and deformation rates. GIA is also proposed as a key process contributing to fault activity and seismicity shortly after the LGM and potentially up to the...
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ftcopernicus:oai:publications.copernicus.org:egusphere110314 2023-11-12T04:18:33+01:00 Glacial isostatic adjustment strain rate – stress paradox in the Western Alps, impact on active faults and seismicity Grosset, Juliette Mazzotti, Stephane Vernant, Philippe 2023-10-18 application/pdf https://doi.org/10.5194/egusphere-2023-538 https://egusphere.copernicus.org/preprints/2023/egusphere-2023-538/ eng eng doi:10.5194/egusphere-2023-538 https://egusphere.copernicus.org/preprints/2023/egusphere-2023-538/ eISSN: Text 2023 ftcopernicus https://doi.org/10.5194/egusphere-2023-538 2023-10-23T16:24:19Z In many regions formerly glaciated during the Last Glacial Maximum (LGM), glacial isostatic adjustment (GIA) explains most of the measured uplift and deformation rates. GIA is also proposed as a key process contributing to fault activity and seismicity shortly after the LGM and potentially up to the present day. Here, we study the impact of GIA on present-day fault activity and seismicity in the Western Alps. We show that, in the upper crust, GIA induces horizontal compressive stress perturbations associated with horizontal extension rates. The latter agree with the observed geodetic strain rates and with the seismicity deformation patterns. Yet, in nearly all cases, the GIA stress perturbations tend to either inhibit fault slip or promote fault slip with the wrong mechanism compared to the seismicity deformation style. Thus, although GIA from the LGM explains a major part of the Western Alp geodetic strain rates, it does not drive or promote the observed seismicity (which must be driven by other processes). This apparent strain rate–stress paradox results from the gradual diminution over time of the finite shortening induced in the upper crust by the Würm ice cap load. A direct corollary of our results is that seismicity and seismic-hazard studies in the Western Alps cannot directly integrate geodetic velocities and strain rates but instead require detailed modeling of the GIA transient impact. Text Ice cap Copernicus Publications: E-Journals |
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Copernicus Publications: E-Journals |
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English |
description |
In many regions formerly glaciated during the Last Glacial Maximum (LGM), glacial isostatic adjustment (GIA) explains most of the measured uplift and deformation rates. GIA is also proposed as a key process contributing to fault activity and seismicity shortly after the LGM and potentially up to the present day. Here, we study the impact of GIA on present-day fault activity and seismicity in the Western Alps. We show that, in the upper crust, GIA induces horizontal compressive stress perturbations associated with horizontal extension rates. The latter agree with the observed geodetic strain rates and with the seismicity deformation patterns. Yet, in nearly all cases, the GIA stress perturbations tend to either inhibit fault slip or promote fault slip with the wrong mechanism compared to the seismicity deformation style. Thus, although GIA from the LGM explains a major part of the Western Alp geodetic strain rates, it does not drive or promote the observed seismicity (which must be driven by other processes). This apparent strain rate–stress paradox results from the gradual diminution over time of the finite shortening induced in the upper crust by the Würm ice cap load. A direct corollary of our results is that seismicity and seismic-hazard studies in the Western Alps cannot directly integrate geodetic velocities and strain rates but instead require detailed modeling of the GIA transient impact. |
format |
Text |
author |
Grosset, Juliette Mazzotti, Stephane Vernant, Philippe |
spellingShingle |
Grosset, Juliette Mazzotti, Stephane Vernant, Philippe Glacial isostatic adjustment strain rate – stress paradox in the Western Alps, impact on active faults and seismicity |
author_facet |
Grosset, Juliette Mazzotti, Stephane Vernant, Philippe |
author_sort |
Grosset, Juliette |
title |
Glacial isostatic adjustment strain rate – stress paradox in the Western Alps, impact on active faults and seismicity |
title_short |
Glacial isostatic adjustment strain rate – stress paradox in the Western Alps, impact on active faults and seismicity |
title_full |
Glacial isostatic adjustment strain rate – stress paradox in the Western Alps, impact on active faults and seismicity |
title_fullStr |
Glacial isostatic adjustment strain rate – stress paradox in the Western Alps, impact on active faults and seismicity |
title_full_unstemmed |
Glacial isostatic adjustment strain rate – stress paradox in the Western Alps, impact on active faults and seismicity |
title_sort |
glacial isostatic adjustment strain rate – stress paradox in the western alps, impact on active faults and seismicity |
publishDate |
2023 |
url |
https://doi.org/10.5194/egusphere-2023-538 https://egusphere.copernicus.org/preprints/2023/egusphere-2023-538/ |
genre |
Ice cap |
genre_facet |
Ice cap |
op_source |
eISSN: |
op_relation |
doi:10.5194/egusphere-2023-538 https://egusphere.copernicus.org/preprints/2023/egusphere-2023-538/ |
op_doi |
https://doi.org/10.5194/egusphere-2023-538 |
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1782335141378523136 |