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.