Jökull - 01.01.2009, Blaðsíða 97

Slope creep in East Iceland observed by InSAR
A1
A2
B1
B2
30
0 m
400
m
500 m
700 m
10
0
m
20
0 m
Skjaldþingsstaðaá
Haugsá
a) 19950718-19950823
−10
−5
0
5
10
[mm]
Svínabakkar
Rauðhólar
0 200 400 600 800 1000 1200
−50
−40
−30
−20
−10
0
10
Distance along profile A1−A2 [m]
LO
S
d
is
pl
ac
em
en
t [
m
m
]
b)
0 200 400 600 800 1000 1200
−50
−40
−30
−20
−10
0
10
Distance along profile B1−B2 [m]
LO
S
d
is
pl
ac
em
en
t [
m
m
]
c)
Figure 5. (a) Geocoded interferogram from 1995 showing slope movement between the Haugsá and Skjald-
þingsstaðaá rivers in Vopnafjörður, above the Svínabakkar farm. (b-c) LOS displacement profiles across the
moving deposits. Multiple profiles in each sub-figure represent several parallel profiles within the correspond-
ing elongated rectangles shown in a. – Bylgjuvíxlmynd frá 1995 sem sýnir hreyfingar í brekkunni fyrir ofan
Svínabakka í Vopnafirði, á milli Skjaldþingsstaðaár og Haugsár. Myndir (b-c) sýna tvö þversnið af hreyfinga-
svæðinu og má sjá allt að 6 cm mælda færslu.
Observed variations in displacement rate of the
deposits can be compared to variations in precip-
itation. Monthly precipitation at Skjaldþingsstaðir
in Vopnafjörður during the time the InSAR data
span varies from around zero to a maximum of over
500 mm during October 1995 (http://www.vedur.is).
Low pass filtering of the monthly values shows clearly
annual precipitation fluctuations peaking in the Fall.
When the maximum LOS displacement value in the
different interferograms is plotted as a function of ei-
ther the mean precipitation rate or accumulated pre-
cipitation during the time the different interferogram
span, no clear correlations can be seen (Jónsson,
2007). A better temporal resolution of both the de-
formation data and the precipitation data is probably
needed to make such a comparison meaningful.
DETECTED SLOPE MOVEMENT AT
OTHER LOCATIONS
Several other locations were discovered in the inter-
ferograms that appear to have active ground move-
ment. These areas have not been inspected in the
field but they all occur on rather steep slopes and
the observed displacements are probably due to ac-
tive slope creep. Two of these areas seem to coincide
with locations catalogued from geomorphological and
geological investigations by Jónsson (1976). These
are Lambadalur valley in Borgarfjörður and Víðivalla-
hraun in Fljótsdalur. The other locations are not in
that catalogue, but these areas include Reykjadalur
in Mjóifjörður, Barðsnes Peninsula, Eyvindarárdalur
valley, Jökulbotnar in Reyðarfjörður, and Loðmundar-
JÖKULL No. 59 97