Jökull - 01.01.2020, Síða 64

The analog seismogram archives of Iceland
Figure 2. Top: The Landsnet seismograph. Drum recorder with a sheet showing a local recording of an earth-
quake swarm in the Hengill area, electronics box, and a loop antenna for the reception of the time signal. The
grey box was used for the field version of the seismograph. Below: The front of the electronics box: Input
for the time signal antenna, seconds filter, tone input for FM modulated signals from a signal receiver, ampli-
fier 0–60 dB, HP-filter, input for geophone signal, LP-filter, 220 VAC power cord, 12 VDC power input. –
Efri mynd: Jarðskjálftamælir Landsnetsins sem hannaður var og smíðaður á Raunvísindastofnun Háskólans.
Á tromlunni er skjálftarit frá mælinum við ÍR-skálann sem sýnir jarðskjálftahrinu á Hengilssvæðinu. Einnig
má sjá „græna kassann“ sem hýsir rafeindabúnaðinn og hringloftnet til móttöku á tímamerki. Grái kassinn í
bakgrunninu var notaður fyrir mælinn þegar mælingar voru gerðar utanhúss. Neðri mynd: Framhlið rafeinda-
kassans: Tengi fyrir tímamerkjaloftnet, sekúndusía, tengi fyrir tón frá móttökutæki þegar skjálftamerki var sent
frá fjarlægum mæli, magnari 0–60 dB, háhleypisía, tengi fyrir merki frá skjálftanema, lághleypisía, snúra fyrir
220 VAC rafmagn, tengi fyrir 12 VDC rafmagn.
The first seismographs of the new network were
installed in the autumn of 1973 and summer of 1974
in South Iceland with emphasis on the Katla volcano.
In the second phase of the project in 1974–1975 seis-
mographs were installed in North Iceland. These sta-
tions showed increased activity around the Krafla vol-
cano, that preceded the first dike injection event of
Krafla that began on December 20, 1975 (e.g., Buck
et al., 2006; Einarsson and Brandsdóttir, 2021). This
led to increased monitoring activity in the Krafla area.
Monitoring was also increased in other areas, includ-
ing the Vatnajökull area and the South Iceland Seis-
JÖKULL No. 70, 2020 61