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Rockslide hazards in Storfjorden, Western Norway - Application of InSAR and other site investigations

Tom R. Lauknes(1), John F. Dehls(2,3), Lars H. Blikra(3) and Yngvar Larsen(1)

(1) Norut, P.O. Box 6434, NO-9294 Tromsø, Norway
(2) Geological Survey of Norway, Trondheim, NO-7491 Trondheim, Norway
(3) International Centre for Geohazards, Trondheim, NO-7491 Trondheim, Norway

Abstract

Tsunamis caused by rockfalls and landslides have taken more than 300 lives in Norway during the last 150 years. Studies of hazards related to rock slope failures are important activities. The documentation of large unstable rock-slope failures at the Åknes and Tafjord in Storfjorden, western Norway initiated a large pilot project funded by the Norwegian government in 2005. The results so far indicate a volume of the unstable slide area at Åknes of 40-70 mill. m3.

Altogether, the project involves about 20 national and international scientific groups. The investigations include both regional mapping in the fjord region and site-specific investigations. The aim of the regional part is to produce hazard and risk maps for the entire fjord region, mainly based on data collected by lidar and air-photos, geological field mapping (landslide inventory, structural geology and spite-specific investigations) and multibeam and seismic data from the fjords. Tsunami modelling and evaluation of run-up zones is integrated in the project.

The site investigations at Åknes include the following data: Geological field data (morphology, structures, fractures), rock-mechanical data, geophysical data (seismic miniarrays for passive monitoring, 2D resistivity, refraction seismics, georadar), detailed laser scans (helicopter and ground based), drill cores, borehole-logging data, movement data from GPS and total station and ground-based interferometric radar. In addition there will be initiated projects on slide dynamics, tsunami modelling and laboratory experiments. The permanent monitoring so far includes 5 extensometers, 2 lasers, climate station, and pore-pressure in one of the drill holes.

Satellite based repeat pass InSAR techniques, using the satellites JERS (L-band), ALOS PALSAR (L-band), ERS-1/2 (C-band), and Envisat ASAR (C-band), will also be investigated in order to identify the slow precursor movements that often characterize both large rock slope failures and soft sediment failures. In order to verify and demonstrate InSAR for deformation monitoring, six 1.8 m trihedral radar corner reflectors have been deployed in Åknes and Tafjord. We present the status of the project, as well as preliminary results of the InSAR processing.

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry