The Icelandic Meteorologal Office operates a sophisticated network of seismographs covering the active zones of the country. Many crustal processes are accompanied by earthquakes, which in turn give important information about the processes. Networks of portable seismographs are frequently used to augment the permanent network in order to study earthquake sequences in more detail. Stress accumulation in the crust is often accompanied by increasing activity of microearthquakes. It may be the result of plate movements or an inflating magma chamber beneath a volcano and can be studied with a network of sensitive seismographs. Aftershocks of large earthquakes tend to occur on the main fault plane responsible for the mainshock. Precise locations of these events give a three-dimensional image of the plane. Similarly, the pathway of magma towards a future eruption site at the surface can be traced by earthquake locations. Sometimes magma travels horizontally along the fissure swarm of a volcano, like happened in Krafla 1975-1984, sometimes the magma travels sub-vertically from the mantle towards the surface, as was documented in the prelude to the eruptions of Eyjafjallajökull in 2010.
Recent publications of the Institute of Earth Sciences on this topic:
Tarasewicz, J., Brandsdóttir, B., White,, R.S., Hensch, M.,Thorbjarnardóttir, B. (2012). Using microearthquakes to track repeated magma intrusions beneath the Eyjafjallajökull stratovolcano, Iceland, J. Geophys. Res., vol. 117, B00C06, doi:10.1029/2011JB008751
Wright, T. J., Freysteinn Sigmundsson, Atalay Ayele, Manahloh Belachew, Bryndis Brandsdottir, Eric Calais, Cindy Ebinger, Pall Einarsson, Ian Hamling, Derek Keir, Elias Lewi, Carolina Pagli, Rikke Pedersen (2012). Geophysical constraints on the dynamics of spreading centres from rifting episodes on land. Nature Geoscience, doi: 10.1038/NGEO1428.
Guðmundsson, Ó. and Bryndís Brandsdóttir (2010). Geothermal noise at Ölkelduháls, SW Iceland.Jökull 60, 89-102.
Brandsdóttir, B., Matthew Parsons, Robert S. White, Ólafur Guðmundsson, Julian Drew and Bergþóra S. Thorbjarnardóttir (2010). The May 29th 2008 earthquake aftershock sequence within the South Iceland Seismic Zone: Fault locations and source parameters of aftershocks. Jökull 60, 23-46.
Soosalu, H., Key, j., White, R.S., Knox, C., Einarsson, P., & Jakobsdóttir, S.S. (2009). Lower-crustal earthquakes caused by magma movement beneath Askja volcano on the north Iceland rift. Bulletin of Volcanology, online, DOI 10.1007/s00445-009-0297-3
Pedersen, R., F. Sigmundsson, P. Einarsson (2007). Controlling factors on earthquake swarms associated with magmatic intrusions; constraints from Iceland. J. Volcanol. Geothermal Res., 162, 73-80.
Buck, W. R., Páll Einarsson and Bryndís Brandsdóttir (2006). Tectonic stress and magma chamber size as controls on dike propagation: Constraints from the 1975-1984 Krafla rifting episode. J. Geophys. Res., 111, doi:10.1029/2005JB003879, B12404, 15 pp.
Soosalu H and Einarsson P. (2006). Seismic characteristics of the Hekla volcano, Iceland, Jökull, 55, 87-106.
Soosalu, H., K. Jónsdóttir and P. Einarsson (2006). Seismicity crisis at the Katla volcano, Iceland - signs of a cryptodome?Journal ofVolcanology and Geothermal Research, 153, 177-186.
Soosalu, H., R. Lippitsch and P. Einarsson (2006). Low-frequency earthquakes at the Torfajökull volcano, south Iceland.Journal of Volcanology and Geothermal Research, 153, 187-199.