Fracturing of the Earth´s crust sometimes extends to the surface and is expressed in characteristic fracture pattern. Precise mapping frequently reveals the mechanism of fracturing and the sense of faulting. En-echelon fracture arrays in the South Iceland Seismic Zone show strike-slip faulting as the main type of faulting along this branch of the plate boundary. They are accompanied by push-up hillocks formed in large earthquakes. Most large earthquakes in South Iceland are formed by faulting on N-S striking faults, perpendicular to the main zone. Fissure swarms of the divergent branches of the plate boundary show where the crust has rifted apart in rifting episodes of earlier times. Geothermal systems tend to form where fluid can percolate within fracture systems in the crust. Fracture mapping is an essential part of the study of geothermal heat.
Map of the fracture systems of the South Iceland Seismic Zone from the paper of Einarsson (2010). Red lines are mapped surface fractures, yellow lines are the source faults of the large earthquakes of 1987, 200, and 2008, according to earthquake studies, InSAR- and GPS-measurements.
Recent publications of the Institute of Earth Sciences on this topic:
Hjartardóttir, Á. R., & P. Einarsson (2011). The Kverkfjöll fissure swarm and the eastern boundary of the Northern Volcanic Rift Zone, Iceland. Bull. Volcanol., doi: 10.1007/s00445-011-0496-6.
Khodayar, M., S. Björnsson, P. Einarsson, H. Franzson (2010). Effect of tectonics and earthquakes on geothermal activity near plate boundaries: A case study from South Iceland. Geothermics, 39, 207-219. Doi:10.1016/j.geothermics.2010.06.003
Hjartardóttir, Á. R., Páll Einarsson and Bryndís Brandsdóttir (2010). The Kerlingar fault, Northeast Iceland: A Holocene normal fault east of the divergent plate boundary. Jökull 60, 103-116.
Einarsson, P. (2010). Mapping of Holocene surface ruptures in the South Iceland Seismic Zone. Jökull 60, 117-134.
Hjartardóttir, Á.R., Einarsson, P. & Sigurdsson, H. (2009). The fissure swarm of the Askja volcanic system along the divergent plate boundary of N Iceland. Bulletin of Volcanology, online, DOI 10.1007/s00445-009-0282-x
Amy E. Clifton & Kattenhorn, S. (2006). Structural architecture of a highly oblique divergent plate boundary segment, Tectonophysics, 419, 27-40.
Clifton, A., P. Einarsson (2005). Styles of surface rupture accompanying the June 17 and 21, 2000 earthquakes in the South Iceland Seismic Zone. Tectonophysics, 396, 141-159.