Regional scale landslide mapping in Northern Norway using SBAS InSAR
Tom R. Lauknes(1,3), Yngvar Larsen(1), John F. Dehls(2), Iain H. C. Henderson(2) and Howard A. Zebker(3)
(1) Norut, P.O. Box 6434, NO-9294 Tromsø, Norway
(2) Geological Survey of Norway, Trondheim, NO-7491 Trondheim, Norway
(3) Stanford University, Department of Electrical Engineering, CA 94305-9515 Stanford, United States
Being a mountainous country, with long steep fjords and valley sides, Norway is particularly susceptible to large rock avalanches. In the last 100 years, over 170 people have been killed by tsunamis in fjords caused by large rock avalanches. In each case, the rock avalanche was preceded by many years of slow movement, with acceleration prior to slope failure. At present, three similar unstable areas have been identified in Norway, and are being monitored using extensive instrumentation. With several thousand kilometers of inhabited coastline and valleys, the challenge we currently face is the identification of similar hazards in an efficient manner.
The Geological Survey of Norway is responsible for landslide mapping throughout the country, and is currently cooperating with Norut AS to establish a Norwegian facility for InSAR processing. The goal is to be able to systematically perform interferometric processing of SAR images from multiple satellites to assist in geohazard mapping and monitoring. InSAR analysis of the almost two decades long time series available in the ERS and ENVISAT archives enables rapid identification of landslides within a large region, allowing geologists to focus field mapping in areas with known hazards. Without the use of such remote sensing tools, it would take decades to map the same area. Once hazardous slopes are identified, continued monitoring using InSAR can be augmented with ground-based systems.
Over 700 ERS and ENVISAT ASAR scenes, covering 19 frames from overlapping tracks, are currently being processed using the Small Baseline Subset (SBAS) algorithm. These scenes cover the area of northern Norway with highest topographic relief, stretching from the Lofoten Islands in the southwest to Alta in the northeast.
Preliminary results, based on ERS scenes from 1992-1999 only, are from around the Lyngen peninsula, just east of the city of Tromsø. Important processing challenges are atmospheric stratification due to high topographic relief and nonuniform temporal sampling due to long winter season, with snow cover possibly lasting from October to May. However, the first results still show remarkably good coherence due to the lack of vegetation above 500-600 m. Numerous areas within the processed area have line-of-sight deformation velocities of up to one centimeter per year. Extensive field checking during the 2007 summer season has identified active fracture systems with evidence of movement in each of these areas.
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,