What causes transient deformations in the Åknes landslide, Norway?

Slow creeping landslides move at rates of millimeters to several meters per year. They can cause extensive damage to infrastructure and pose a major threat to human lives if failing catastrophically. Landslides can progressively weaken over time by rock mass damage processes that may occur by constant slow creep or sudden transient slips. Eventually, damage can lead to strain localization along the basal shear plane and catastrophic failure of the landslide. When observed, transient slip events, also called creep bursts, may induce short-term loading and hence can control landslide stability. These creep bursts correspond to short periods that can last several days where the displacement of a landslide accelerates and then decelerates. Here, we compiled and analyzed extensive multiphysics data series of the Åknes landslide, Norway. This landslide is moving at a slow rate of 6 cm per year and could generate a large tsunami wave in a fjord if it would rupture catastrophically. Based on the time series of an array of eight seismometers, five extensometers, seven borehole inclinometers and piezometer strings, and ten continuous GPS stations sampled with time resolutions down to 5 minutes over several years, we detected creep bursts in this landslide. These events interact with a distinct creep trend related to seasonal variations of rainfall and snowmelt. We analyze the creep bursts in regards to micro-earthquake activity and water pressure levels, to study their origin.