Overlapping rift‐zone segments and the evolution of the South Iceland Seismic Zone

Abstract

The South Iceland seismic zone is a 20–60 km‐wide (north‐south) and up to 70 km‐long zone of north and north‐northeast trending Holocene arrays of en echelon tension fractures. These fracture arrays are related to dextral strike‐slip faults buried by Holocene lava flows. In this zone, major destructive earthquake sequences occur at intervals of 45–112 years, the largest events reaching magnitude 7 (Ms). We propose that this seismic zone is located between overlapping rift‐zone segments (spreading centers), where the eastern segment has been propagating to the south during the past 3 Ma. We made a finite element study of this configuration with the segments modeled as mode I cracks loaded in tension. The results suggest that the South Iceland seismic zone in general, and the north and north‐northeast trending dextral faults in particular, develop in response to the shear stresses generated between the rift‐zone segments.