Jökull - 01.06.2000, Side 6

Eysteinn Tryggvason
Figure 2. Sketch map of the Mýrdalsjökull area in south Iceland, showing major rivers, ice caps (shaded) and
optical levelling tilt stations (triangles). Also shown are calderas and the 1918 eruption site (crosses) of the
Katla volcano. (After Jóhannesson et al., 1990). - Kort af Mýrdalsjökli og nágrenni þar sem sýndar eru helstu
ár, mœlistöðvar (þríhyrningar) og staðsetning Kötlugossins 1918 (krossar) við austurbrún Kötluöskjunnar.
Fimmvörðuháls tilt station was interpreted as caused
by magma intrusion below the volcano Eyjafjalla-
jökull (Dahm and Brandsdóttir, 1997). This intrusi-
on may have caused the observed ground tilt between
observations of September 1993 and September 1994.
Observed tilt at the two stations Kötlukriki and
Jökulkvísl east of Mýrdalsjökull, and also east of
Katla, is generally small, frequently 2 to 4 /irad
(Figure 3).
The ground tilt observations near Katla are of
variable quality because of different foundation at
the stations. Of the three stations, Höfðabrekkuheiði,
Kötlukriki and Jökulkvísl, the last named station is
clearly giving data of best quality. The standard error
of observed ground tilt is usually less than 0.5 prad,
with no deterioration of the result with increased time
between measurements, but the ground tilt is compu-
ted from two measurements made at different times.
4 JÖKULL No. 48