Earthquake fractures in the districts Land and Rangárvellir in the South Iceland seismic zone (Jarðskjálftasprungur á Landi og Rangárvöllum)

Large earthquakes have been accompanied by extensive surface fracturing throughout the South Iceland Seismic Zone, one of the major fracture zones of the Mid-AÚantic plate boundary.Fracture systems in the eastemmost part of the zone, in the districts Land and Rangárvellir, have been mapped.The fractures generally strike NE and form en echelon arrays which trend N-S.They are interpretedas the surface expression of underlying righl-lateral strike-slip faults.Thefaults are arranged side by side within the E-W Fig. 1.Map of the seismic zones of Southwest Iceland showing fissure swarms associated with crustal spreading, the seismic zone on Reykjanes peninsula, and destruction zones ofmajor earthquakes in South Iceland since 1700 (from P. Einarsson et al. 1981).Mynd 1. Yfirlitskort af Suðvesturlandi.Sýndir eru sprungusveimar á Reykjanesskaga og í vestara gosbeltinu, einnig skjálftabeltið á Reykjanesskaga og tjónasvoeði hetstu jarðskjálfta á Suðurlandsundirlendi síðan 1700.Myndin er tekin úr grein Páls Einarssonar o.fi.1981).JÖKULL 32.ÁR 113trending seismic zone.The reason Jor this unusual configuration is poorly understood, but the tentative explanation is given, that the seismic zone is afracture Jront migrating southwards in response to a southwards propagation oj the eastern rift zone oj Iceland.