The South Iceland Seismic Zone: tectonic and sismotectonic analyses revealing the evolution from rifting to transform motion

摘要: Abstract The South Iceland Seismic Zone (SISZ) trends E–W between two major volcanic rift zones of Southern Iceland. It is 20–60 km wide and 70 long, characterized by important seismotectonic activity. Major destructive earthquakes in the SISZ were reported throughout centuries, from initial settlements until now. We carried out a structural study this area, including analysis aerial photographs, local observation faults collection minor fault slip data outcrops, as well an focal mechanisms earthquakes. At regional scale, main are approximately NNE–SSW NE–SW. ENE–WSW, NW–SE WNW–ESE trending also detected photographs field. All these normal or strike-slip character. Some historical earthquake fractures observed post-glacial lava flows SISZ: most right-lateral trend roughly N–S. trace left last single M7 1912, mentioned case example. In addition to large-scale faults, we analyzed more than 700 at 25 sites. Most sites located rocks Upper Pliocene–Pleistocene age. Inversion sets enabled us reconstruct paleostress tensors, hence define tectonic regimes which have prevailed SISZ. Examples characteristic given, results presented. Two groups faulting reveal distinct stress regimes, with perpendicular directions extension, (primary) NE–SW (secondary). Both groups, however, display inhomogeneous sets, related extensional faulting. primary regime agreement both general behaviour left-lateral transform zone opening segments. secondary regime, incompatible interpreted terms permutations. A population 231 double couple (M>1 depth > 2 km) was states. show great similarity directions. present-day field mainly inferred analyses consistent present zone. However, proportion within seismic activity (71%) significantly higher that revealed geological Quaternary (50%). This contrast development evolution fields identified formations reflect previous when it inside zone, its thus illustrating rifting motion.