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What causes creep bursts in the Åknes landslide, Norway?
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  • Andreas Aspaas,
  • Pascal Lacroix,
  • Clara Sena,
  • Lene Kristensen,
  • Nadège Langet,
  • François Renard
Andreas Aspaas
University of Oslo

Corresponding Author:[email protected]

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Pascal Lacroix
ISTerre/IRD/UGA/CNRS
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Clara Sena
University of Oslo
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Lene Kristensen
Section for Landslides and Avalanches, Norwegian Resources and Energy Directorate, Trondheim, Norway
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Nadège Langet
Department of Applied Seismology, NORSAR, Lillestrøm, Norway
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François Renard
University of Oslo
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Abstract

Slow-creeping landslides may fail catastrophically, posing significant threats to infrastructure and lives. Landslides weaken over time through rock mass damage processes that may occur by slow steady-state creep or transient accelerations of slip, called creep bursts. Creep bursts may control landslide stability by inducing short-term damage and strain localization. This study focuses on the Åknes landslide in Norway, which moves up to 6 centimetres per year and could potentially trigger a large tsunami in the fjord lying below. Here, an eleven-year dataset is compiled and analyzed, including kinematic, seismic, and hydrogeological data acquired at the landslide surface and in a series of boreholes. Creep bursts with millimetre amplitude are detected in the landslide’s shear zone. An annual average of two creep burst events have been recorded within the shear zone in each borehole, accounting for approximately 11% of the total displacement. Creep bursts phased over multiple boreholes are preceded by increased seismic activity and water pressure increase. However, most creep bursts are observed in only one or a few boreholes. Creep bursts often occur during the seasonal high and low levels of groundwater, correlating with local peaks in water pressure, but no such correlation is observed during summer. We propose that on one side, the progressive wear of asperities leads to creep bursts being uncorrelated to water pressure changes. Conversely, enhanced stress corrosion causes creep bursts to correlate to water level fluctuations. Our findings offer unique insights into landslide mechanics, correlating shear zone dynamics with surface displacement and environmental parameters.
15 Mar 2024Submitted to ESS Open Archive
15 Mar 2024Published in ESS Open Archive