Mechanisms of the faults of 17 and 21 June 2000 earthquakes in the South Iceland Seismic Zone from the surface traces of the Arnes and Hestfjall faults

Two major earthquakes (M-s=6.6) occurred on 17 and 21 June 2000 in the Sout h Iceland Seismic Zone. This paper presents characteristic examples of surf ace traces of these seismic faults, called the Ames and Hestfjall faults. T he surface trace of the Arnes fault at Mykjunes shows a conjugate strike-sl ip pattern with a N30 degreesE trending right-lateral fault and a N60 degre esE trending left-lateral fault. Each of these faults is formed by 'en-eche lon' arrays of fractures and push-ups. The surface trace of the Hestfjall f ault near Bitra reveals a N50 degrees -60 degreesE trending left-lateral st rike-slip fault including large open fractures, 'en-echelon' fractures and some push-ups. These observations show that the actual earthquake-related f ault pattern is not restricted to the north-south-trending dextral strike-s lip revealed by focal mechanisms and north-south alignment of aftershocks, but includes conjugate systems consistent with the structural pattern of th e SISZ. (C) 2001 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.