Tectonic investigation of Nahanni earthquake area Northwest Territories (Canada) using JERS-1 and ERS-1 SAR data

The Nahanni region, Northwest Territories, Canada is a seismically very active remote area. There have, recently, been several large earthquakes near the North Nahanni River including the ones on 5 October 1985 (Ms 6.6), 23 December 1985 (Ms 6.9) and 25 March 1988 (Ms 6.2). The earthquakes occurred within a small relatively undeformed plateau, the Mackenzie Plain, in the Foreland Fold Belt created along the northeastern Cordillera during the Columbia or Laramide Orogeny. As a part of the JERS-1 science verification program (0202), investigation of the tectonic features of the Nahanni earthquake area was planned, and the JERS-1 SAR, ERS-1 SAR, SPOT and Landsat image data sets were acquired in addition to other geophysical data sets such as earthquake epicenter data for main- and after-shocks. Objectives of data processing and digital data fusion experiment were to enhance and image the surface tectonic signatures. Detailed investigation of the surface structural features in the preprocessed individual as well as the final integrated composite images over the epicentral area indicates that there are several previously unmapped structural features intersecting the major northwest trending Iverson thrust fault and accompanying structures at the centre of the epicentral region. Focal plane solution of selected main and after shocks also confirms the new tectonic interpretation utilizing the JERS-1 and ERS-1 SAR data. It, however, appears that the Iverson thrust fault is non-seismic and tectonically stable.