Jökull - 01.01.2010, Blaðsíða 119

Holocene surface ruptures in the South Iceland Seismic Zone
Figure 1. Index map of the plate boundaries in Iceland and volcanic systems is adapted from Einarsson and
Sæmundsson (1987). Rectangle shows the study area. Lower image: Surface fractures in the SISZ, exposed in
Holocene formations, shown with red lines. Double yellow lines show the source faults of the 1987 (Bjarnason
and Einarsson, 1991), 2000 (Hjaltadóttir, 2009) and 2008 (Decriem et al., 2010) earthquakes. Background
is from SPOT Image. – Yfirlitskort af eldstöðvakerfum og flekaskilum á Íslandi. Rauður ferhyrningur af-
markar rannsóknasvæðið. Neðri mynd: Yfirborðssprungur á skjálftasvæði Suðurlands, sem sjá má ummerki
um í jarðmyndunum frá Nútíma, kortlagðar með GPS-tækni. Gular línur sýna upptakamisgengi skjálfta við
Vatnafjöll 1987, skjálfta í júní 2000 og maí 2008.
major earthquake sequence within the next decades.
The original forecast gave a 80% probability for the
occurrence of a major earthquake sequence within the
next 25 years (i.e. within the 1985–2010 time win-
dow). This forecast was fulfilled in 2000 when two
magnitude 6.5 (Mw) events occurred, accompanied by
several triggered magnitude 5 events along the SISZ
and the adjacent plate boundary branch on the Reykja-
nes Peninsula (e.g. Einarsson, 2001, 2002, Stefáns-
son et al., 2001, Árnadóttir et al., 2004). A dou-
ble event occurred again in 2008 that appears to have
consisted of subevents of magnitude 5.9 and 6.1, re-
spectively, on two parallel faults in the western part
of the zone (Decriem et al., 2010, Halldórsson et al.,
2009, Hreinsdóttir et al., 2009). The sequence may
not be over yet at the time of writing (Sept. 2010)
as only part of the potential seismic moment accumu-
lated since 1896 has been released (Decriem et al.,
2010).
JÖKULL No. 60 119