HR: 0800h
AN: H41G-0843    [Abstracts]
TI: The dynamics of active landslide development and evolution: a combined structural geology, geomorphology and InSAR approach.
AU: Henderson, I H
EM: iain.henderson@ngu.no
AF: Geological Survey of NOrway, Leif Eiriksson Veg 39, Trondheim, 7491, Norway
AU: * Lauknes, T
EM: tomrune@itek.norut.no
AF: NORUT, PO Box, Tromsų, 9294, Norway
AU: Osmundsen, P
EM: per.terje.osmundsen@ngu.no
AF: Geological Survey of NOrway, Leif Eiriksson Veg 39, Trondheim, 7491, Norway
AU: Redfield, T
EM: tim.redfield@ngu.no
AF: Geological Survey of NOrway, Leif Eiriksson Veg 39, Trondheim, 7491, Norway
AU: Larsen, Y
AF: NORUT, PO Box, Tromsų, 9294, Norway
AB: In recent years structural geology has been used as a tool to investigate the development and evolution of potential rockslides. Recent studies have been mostly concentrated on identifying particular geometrical constellations suitable for sliding to occur and the observed kinematics. Limited emphasis on the direct relationships between the development of structures, evidence for movement, and its effect on the geomorphological architecture have been described. A reconciliation between field observations and various standard measuring techniques has often proven ambiguous or problematic. However, recent technological advances in interferometric synthetic aperture radar (InSAR) satellite technology provide a new measurement method to determine potential rockslide movement and therefore provide a direct link between qualitative movement data and field observations of structures, kinematics and geomorphological change in slope. We present structural and geomorphological observations from the Gamanjunni slide in Troms, Norway, combined with detailed InSAR deformation measurement data based on analysis of ERS-1/2 SAR data in the 1992--1999 timeframe, to determine the detailed activity, evolution and detailed magnitude of displacement. The slide is located on a west-facing mountainside at a height of 1200m and is made up of two angled back-scarps with a 20-30° basal sliding plane which outcrops at the front of the moving block. On a locality scale we can demonstrate that InSAR documents active landslide movement which is in agreement with several different observation types in the field. The spatial extent of the InSAR movement area also fits extremely well with the area delimited by active structures. In detail at a sub-locality scale, InSAR is also able to document structural processes in the moving block. Oblique kinematics means that the two angled fault scarps have different movement rates. This is reflected in the observed, differential activity of the two fault scarps which is directly reflected in a different movement magnitude in the InSAR data. We also document a segmental, partial reactivation of one of the scarps which is reflected in the InSAR data as an along strike variation in InSAR movement. Field evidence suggests that some fault segments have been active at different times and that previously active fault segments, which are now dead, have been superceded by newer, more active faults which are now accommodating present movement. This is also reflected in the details of the InSAR data. Therefore we conclude that InSAR is an essential tool in providing quantitative data of the activity in landslides and an important confirmation of the field observations for recent movement activity. However, we go further in suggesting that the InSAR greatly extends our knowledge on the processes and evolution of fault scarp development and therefore active slide evolution.
DE: 8100 TECTONOPHYSICS
SC: Hydrology [H]
MN: 2007 Fall Meeting