Strain accumulation 1986–1992 across the Reykjanes Peninsula Plate Boundary, Iceland, determined from GPS measurements

GPS geodetic observations 1986–1992 spanning the oblique plate boundary on the Reykjanes Peninsula, SW Iceland, show that left‐lateral shear strain is accumulating in the area. The principal strain rates are: έ₁=0.255 ± 0.055 µstrain/yr (extension) at N121 ± 6°E, and έ₂=‐0.190 ± 0.053 µstrain/yr (contraction) at N31 ± 6°E. The principal axis of extension is perpendicular to the strike of fractures within volcanic systems on the Peninsula. The direction of maximum left‐lateral shear strain is N76 ±6°E, the same as the trend of the seismic zone on the Peninsula. Tensor shear strain in this direction is −0.222±0.054 µstrain/yr. Continuous aseismic slip of the North American‐Eurasian plates below a 5–11 km locking depth on the Peninsula can explain the observed depth of earthquakes, the width of the deformation zone determined from recent fissuring and faulting, and the GPS‐measurements of strain.