Detailed rockslide mapping in northern Norway with small baseline and persistent scatterer interferometric SAR time series methods T.R. Lauknes a, ⁎, A. Piyush Shanker b , J.F. Dehls c,1 , H.A. Zebker b , I.H.C. Henderson c , Y. Larsen a a Norut Tromsø AS, P.O. Box 6434, Forskningsparken, NO-9294 Tromsø, Norway b Depts. Of Electrical Engineering and Geophysics, Stanford University, 350 Serra Mall, Packard 334, Stanford, California 94305, USA c Geological Survey of Norway, P.O. Box 6315 Sluppen, NO-7491 Trondheim, Norway abstract article info Article history: Received 15 December 2009 Received in revised form 9 April 2010 Accepted 17 April 2010 Keywords: Small baseline SBAS PSI Rockslides SAR interferometry Ground displacements Rockslides have a high socioeconomic and environmental importance in many countries. Norway is particularly susceptible to large rockslides due to its many fjords and steep mountains. One of the most dangerous hazards related with rock slope failures are tsunamis that can lead to large loss of life. It is therefore very important to systematically identify potential unstable rock slopes. Traditional landslide monitoring techniques are expensive and time consuming. Differential satellite interferometric synthetic aperture radar (InSAR) is an invaluable tool for land displacement monitoring. Improved access to time series of satellite data has led to the development of several innovative multitemporal algorithms. Small baseline (SB) methods are based on combining and inverting a set of unwrapped interferograms that are computed with a small perpendicular baseline in order to reduce spatial phase decorrelation. Another well proven technique is the persistent scatterer interferometric method (PSI) that is based on analysis of persistent point targets. In this paper, we apply both approaches to study several rockslide sites in Troms County in the far north of Norway. Moreover, we take the opportunity to address the difference and similarities between the SB and the PSI multitemporal InSAR methods for displacement studies in rural terrain. © 2010 Elsevier Inc. All rights reserved. 1. Introduction 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 (Eiken, 2008; Ganerød et al., 2008). With several thousand kilometres of inhabited coastline and valleys, it is a challenge to identify similar hazards in an efficient manner. Once we suspect an area to be sliding, it may take several years of measurements to confirm it and extensive ground instrumentation to characterize the type of motion. The evolution of potential rockslides has often been studied using structural geological methods (Agliardi et al., 2001; Braathen et al., 2004; Chigira, 1992). Recent studies have concentrated on document- ing rockslide kinematics and identifying geometric configurations particularly susceptible to sliding (e.g., Braathen et al., 2004; Henderson & Saintot, 2009). Less emphasis has been placed on the direct, empirical relationships between the development of struc- tures, evidence for movement and subsequent effects on the geomorphological architecture (Colesanti & Wasowski, 2006). Rec- onciliation between field observations and conventional measuring techniques such as Global Navigation Satellite System (GNSS) receivers and Total Station measurements has often proven ambig- uous or problematic. Such quantification is a necessary step in hazard and risk assessment (Solheim et al., 2005). Recently, the potentiality of differential synthetic aperture radar (InSAR) approach has been investigated to study landslides (Berar- dino et al., 2003; Colesanti & Wasowski, 2006; Hilley et al., 2004; Rott & Nagler, 2006; Strozzi et al., 2005). The satellite based InSAR technique involves comparing the phase information from two SAR images to potentially detect millimeter to centimeter scale ground deformation patterns (Gabriel et al., 1989). Over the last decade, interferometry has become an important tool for mapping Remote Sensing of Environment 114 (2010) 2097–2109 ⁎ Corresponding author. E-mail addresses: Tom-Rune.Lauknes@norut.no (T.R. Lauknes), shanker@stanford.edu (A. Piyush Shanker), John.Dehls@ngu.no (J.F. Dehls), zebker@stanford.edu (H.A. Zebker), Iain.Henderson@ngu.no (I.H.C. Henderson), Yngvar.Larsen@norut.no (Y. Larsen). 1 Currently with Alberta Geological Survey, 4999 98 Ave. NW, Edmonton, AB T6B 2X3, Canada. 0034-4257/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.rse.2010.04.015 Contents lists available at ScienceDirect Remote Sensing of Environment journal homepage: www.elsevier.com/locate/rse