Detecting co-seismic displacements in glaciated regions: An example from the great November 2002 Denali earthquake using SPOT horizontal offsets

• Published in: Earth and Planetary Science Letters
• Main Authors: Taylor, Michael H., Leprince, Sebastien, Avouac, Jean-Philippe, Sieh, Kerry
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier 2008
• Subjects: Alaska; Denali earthquake; earthquake rupture; SPOT offsets; glacier
• Online Access: https://doi.org/10.1016/j.epsl.2008.03.028

We use SPOT image pairs to determine horizontal offsets associated with the Mw 7.9 November 2002 Denali earthquake in the vicinity of Slate Creek, AK. Field measurements and aerial photographs are used to further characterize the geometry of the surface rupture. Aerial photographs show that shear localization occurs where the rupture trace is linear, and distributed off-fault deformation is common at fault bends and step-overs, or at geologic contacts between rock, glacial sediments, and ice. The displacement field is generated using a sub-pixel cross correlation technique between SPOT images taken before and after the earthquake. We identify the effects of glacier motion in order to isolate the tectonic displacements associated with the Denali earthquake. The resulting horizontal displacement field shows an along-strike variation in dextral shear, with a maximum of approximately 7.5 m in the east near 144° 52′W, which decreases to about 5 m to the west near 145° 45′W. If the November 2002 earthquake represents the long-term behavior of the Denali fault, it implies a westward decrease in the long-term dextral slip rate. A possible mechanism to accommodate the westward decreasing slip on the Denali fault is to transfer fault slip to adjacent east-trending contractional structures in the western region of the central Alaskan Range. © 2008 Published by Elsevier B.V. Received 14 September 2007. Received in revised form 27 February 2008. Accepted 9 March 2008. Available online 25 March 2008 M. Taylor thanks the Tectonics observatory at Caltech for partial support during this research. We are grateful to Aron Meltzner for careful scanning of the aerial photographs. This study has benefited from discussions with David Schwartz, Peter Haeussler, An Yin, Gilles Peltzer, Aron Meltzner, Francois Ayoub, Alex Robinson, Doug Walker, and Anne Sophie-Meriaux, which were extremely helpful in organizing our thoughts. We appreciate the constructive comments made by two anonymous reviewers that helped to clarify several ...