Statistical Analysis of Small Faults in Rotated Blocks of Crust Near the Húsavík-Flatey Transform Fault, Northern Iceland

Abstract

The dextral Húsavík-Flatey fault, in northern Iceland, provides a unique opportunity to observe an oceanic transform fault on land. Structural and paleomagnetic measurements from lavas and dikes on Flateyjarskagi peninsula indicate that rocks adjacent to the fault have rotated clockwise more than 100°. We examine the effect of this rotation on the orientations of small faults that developed in rocks adjacent to the transform fault. We also use patterns in small-scale data to build on models of the style of deformation surrounding the fault. We apply statistical tools including spatial regressions to structural data to estimate the amount of distributed shearing around the transform fault, and to predict the orientations of rotated structures. Some small faults are consistent with predicted rotations, while others are consistent with the modern kinematics, suggesting that they postdate block rotation. This protracted temporal history for small faults complicates paleostress interpretations from rocks adjacent to the Húsavík-Flatey fault. Previous studies assumed the small faults formed in their modern orientations and attributed their variability to stress variations, whereas we identify populations of faults that have likely rotated to their present-day attitudes.