Seismic risk in Northern Iceland: Deformation maps of Tjörnes peninsula computed from INSAR.

• Main Authors: O. Henriot, T. Villemin, F. Jouanne, Le Bourget, Du Lac Cedex
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Husavik; Kolbeinsey; Kolbeinsey Ridge; Krafla; Tjörnes; Iceland
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.533.9129; http://earth.esa.int/pub/ESA_DOC//fringe1999/Papers/henriot.pdf

The Tjörnes Fracture Zone (TFZ) is a dia-mond shaped transform zone between the offshore Kolbeinsey ridge and the onland North Iceland Rift Zone (Fig. 1). Its southern border is a 100km long N120°E dextral strike-slip zone, a few kilo-metres offshore North of the island for 2/ 3 rds of its length. Historically, it is a seismically very active segment with dextral strike-slip and normal mecha-nisms. Pull-apparts and pressure-ridges are char-acteristic of its onland section. The eastern tip is abruptly cut off by one of the fault zones of the North Iceland Rift Zone. Following the 1975 to 1984 Krafla rifting event, the seismic activity of the Husavik fault decreased considerably. It remained negligible for more than eight years. This change can be explained by a sudden stress increase, fol-lowing the rifting episode, which would have blocked the fault. However, aseismic movement is not to be excluded. The DIAPASON software, developed at the CNES, is used to form interferograms of SAR scenes from the ERS1 and ERS2 satellites cover-ing the transform fault and its junction with the rift zone. We used 13 scenes, acquired between 1992 and 1998 on two parallel satellite tracks, in order to calculate 36 interferograms with temporal values of up to six years, i.e. potential displacements reaching 12cm across the transform fault. The large number of interferograms allowed us to dis-criminate between crustal deformation and atmos-pheric or topographical artefacts, the first being always present with the same intensity regardless of temporal spacing of scenes and the latter being closely linked to the topography. These observations will allow us to deter-mine the behaviour of the transform fault after a major rifting episode, particularly with respect to the relative importance of aseismic movement and locked state for the TFZ.