Jökull - 01.01.2010, Blaðsíða 110

Hjartardóttir et al.
Figure 7. The Kerlingar fault, visible as a depression filled with snow. View towards the south. – Snjóskaflar
sýna staðsetningu Kerlingamisgengisins vel. Horft til suðurs.
DISCUSSION
We have mapped and conducted field studies of the
Kerlingar fault to get a better constraint on its ori-
gin. The Kerlingar fault is, in many respects, different
from the vast majority of fractures within the NVZ.
The fault is unusually long and has a throw down to
the east, although it is located in the easternmost part
of the NVZ. Rift zones are usually manifested as gen-
tle graben structures with boundary faults dipping in-
ward. In addition, the fault strikes obliquely to the
fissure swarms of the NVZ at this latitude, although
it is both parallel with the line of central volcanoes
in the NVZ, which includes Fremrinámar, Krafla, and
Þeistareykir, and with the NVZ-EFB boundary. The
fault is located within an area of hyaloclastite ridges,
which extends along the boundary between the NVZ
and the EFB (Figure 1). There, several faults have
similar orientation as the Kerlingar fault. These un-
usual attributes of the Kerlingar fault might indicate
that the fault was formed and/or reactivated by pro-
cesses which affect the NVZ area as a whole.
Sense of faulting
The rift zones of Iceland are predominantly made up
of normal faults. Some structures previously sug-
gested to be due to thrust faulting have turned out to
be of local origin (Khodayar and Einarsson 2004). In
general, intraplate earthquakes in young (10–20 m.y.)
crust (such as the Icelandic crust) are caused by nor-
mal faulting, while thrust faulting is predominant in
older crust (e.g. Sykes and Sbar 1974). Indeed, the
Kerlingar fault has characteristics which may indicate
that it is a normal fault, as it is continuous, as opposed
to the segmented and sinuous fault structure that often
characterizes thrust faults.
110 JÖKULL No. 60