Since the start of the earthquake swarm, precise continuous GPS stations located in the vicinity of the Bárðarbunga central volcano have shown movements which indicate that magma is propagating in the crust. During the period between 8 am on the 15th of August and 4 pm on the 18th of August a GPS station on Dyngjuháls moved 5,4 cm towards the northwest and a GPS station near Grímsvötn moved 1,8 cm towards the south.
The map shows locations of earthquakes detected by the SIL network of the Icelandic Meteorological Office. Movements on continuous GPS stations are shown as blue arrows, the continuous stations are run in cooperation between the Institute of Earth Sciences at the University of Iceland and by the Icelandic Meteorological Office. Fractures and eruptive fissures in the area are denoted by yellow and red lines respectively.
The orange arrows show a model on how the GPS stations could be moving if a dike was propagating (see thick red line on map), and magma was draining away from the Bárðarbunga magma chamber („Mogi center“). It has to be mentioned, however, that this model is only one of several models that can explain the movements seen on the GPS stations.
Possible model of the dike intrusion:
Length of dike: 20 km
Height of dike: 2,1 km
Opening of dike: 1,6 m
Depth to the dike: 3 km
Volume of dike: 80-90 million cubic meters
Strike = 47,51, dip 90 (predefined)
Depth to Mogi source: 1 km
Volume change of Mogi source:
-10 til -30 million cubic meters
GPS data – Institute of Earth Sciences, University of Iceland and the Icelandic Meteorological Office
Model calculations: Elías Rafn Heimisson, Freysteinn Sigmundsson
Earthquakes: Icelandic Meteorological Office (part of the earthquakes have not been reviewed).
Fractures near Tungnafellsjökull: Þórhildur Björnsdóttir and
Páll Einarsson (Jökull, 2013).
Fractures and eruptive fissures in the Northern Volcanic Zone: Ásta Rut Hjartardóttir
and Páll Einarsson (2012), Ásta Rut Hjartardóttir (2013).
Background: IS50 database of the National Land Survey of Iceland.