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Útdráttur:
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In June 2000, two M=6.5 earthquakes occurred in the South Iceland Seismic Zone (SISZ) (Árnadóttir et al. 2001; Pedersen et al. 2001; Pedersen et al. 2003; Stefánsson et al. 2003; Clifton and Einarsson 2005). Following the earthquakes, seismicity greatly increased in all of southwestern Iceland. Roughly nineteen thousand microearthquakes, recorded by the SIL seismic network between June and December 2000 and interactively analyzed, have been relatively located using a multi-event relocation method. The procedure increases location accuracy to such a degree that fault patterns defined by the microearthquake distribution may become resolvable. Joint interpretation of the event distribution and focal mechanisms allows definition of common fault planes and the determination of slip directions on these faults. The mapped area includes the South Iceland Seismic Zone, the Reykjanes Peninsula (RP) and an area surrounding the Geysir geothermal system on the eastern margin of the Western Volcanic Zone (WVZ). The mapping reveals finer details of the faults which ruptured in the two M=6.5 events, and shows an interesting difference between their fault patterns. Numerous other smaller faults and clusters, which were illuminated by the increased activity, are also mapped. These mostly show the common northerly striking trend observed on the surface, with near vertical fault planes and right-lateral slip, accompanied by a vertical component. In some areas deviation from this trend is seen and westerly striking faults are observed, exhibiting left-lateral movement. The mapped events are shown in Figure 1. |
