Jökull - 01.12.1989, Síða 36

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Fig. 2. The three geodetic figures in the South Iceland Seismic Zone, stations are marked with name and sta-
tion numbers. Epicenters are from the period 1982-85, located by the Icelandic seismic net. The most prom-
inent earthquake cluster is related to the Hengill geothermal area, which is hachured. Mapped surface rup-
tures of major earthquakes in the Postglacial time are also shown.
Mynd 2. Mælinetin þrjú á Suðurlandi, í Ölfusi, Flóa og Holturn. Mœlipunktar eru merktir með tölustöfum.
Upptök jarðskjálfta árin 1982-85 eru sýnd með hringjum. Þau eru staðsett með Landsneti skjálftamœla. Þétt-
astir eru skjálftarnir á Hengilssvœðinu og eru þeir þar að nokkru leyti tengdir jarðhitasvœðinu, sem er ská-
strikað. Einnig eru sýnd helstu kerfi jarðskjálftasprungna, sem virkar hafa verið á nútíma.
DATA AND METHODS
A total of 19 distances were measured with an
AGA laser geodimeter, model 6BL. Line lengths
varied between 1.6 and 12 km. Details of the meas-
urements, individual readings and descriptions of
the survey points are given by Erlingsson and Ein-
arsson (1985). For atmospheric corrections air
34 JÖKULL, No. 39, 1989
temperature and pressure were sampled at both ends
of the lines before and after each measurement. A
mean value of the readings was used for the correc-
tions. For tilting lines corrections were also made
for the differential height of the tripods, reducing the
measurements to the slope distance between the
bench marks. Elevation differences necessary for
í