Háskóli Íslands

8 March 2021 - 16:21

Civil Protection Service’s Science Council convened by video conference today to discuss the swarm of earthquakes on the Reykjanes peninsula. The meeting was attended by experts from the Icelandic Meteorological Office, the University of Iceland, ÍSOR, the Environment Agency of Iceland, the Icelandic Institute of Natural History; as well as representatives from Reykjavík Energy, the Icelandic Directorate of Health, Isavia-ANS, and HS-Orka.
During the meeting, attendees reviewed the weekend’s activity, as well as reviewing readings and data recorded over the past 24 hours.

The picture shows a demarcated area where the magma tunnel is forming under the earth’s crust. When magma flows into the strata and forms magma tunnels, as is currently the case in the area of unrest between Keilir and Fagradalsfjall, pressure is formed in the earth’s crust. This creates tension to the east and west of the area of unrest, and a likely explanation for the earthquakes that occur there is that these are so-called „remotely-triggered earthquakes“ which are signs of stress release, but do not indicate that magma is moving in the areas where they are detected. Examples of such earthquakes could be seen on the night before Sunday, March 7, when many powerful earthquakes were measured over a short period of time.

Main Conclusions of the Meeting

  • In the case of an eruption, the conclusion remains that a fissure would form somewhere in the area bounded by Fagradalsfjall and Keilir, where the magma tunnel is forming. There is no evidence of magma movements outside of this area.
  • The most probable source of the magma, based on the volcanic activity of the past few days, has been traced to the southern part of the magma tunnel.
  • The latest satellite images, GPS readings, and model calculations indicate that the magma flow has subsided since the beginning of last week. The magma is not at a great depth, and therefore, we must continue to assume the possibility of an eruption.
  • If the magma tunnel continues to expand over the coming days and weeks, we can expect similar earthquake bursts as occurred during the weekend.

At a meeting of the Scientific Council today, satellite images received yesterday were reviewed and compared to GPS readings, seismic data, and other measurements. Seismic activity has somewhat decreased since last weekend. On Saturday evening, seismic activity in Fagradalsfjall increased significantly, and this increased activity lasted from approximately 18:00 to 23:00. Just after midnight, the night before Sunday, a disturbance began that lasted for about 20 minutes, and was followed, shortly after, by a magnitude 3.8 earthquake. As a result, activity increased further, and several strong earthquakes were detected. The largest earthquake measured at 5.1 in magnitude, at 02:02.

In the case of an eruption, the conclusion remains that a fissure would form somewhere in the area bounded by Fagradalsfjall and Keilir, where the magma tunnel is forming. There is no evidence of magma movements outside of this area. The most probable source of the magma, based on the past few days’ volcanic activities, has been traced to the southern part of the magma tunnel. The latest satellite images, GPS readings, and model calculations indicate that the magma flow has subsided since the beginning of last week. The magma is not at a great depth, likely reaching as high as 1km below the surface, and therefore we must continue to expect an eruption.

The Effect of the Magma Tunnel on Other Areas on the Reykjanes Peninsula

When magma flows into the strata and forms magma tunnels, as is currently the case between Keilir and Fagradalsfjall, the pressure is formed in the earth’s crust. This causes shifts in stress for a large area around the tunnel. Model calculations show that these shifts in stress can generate so-called „remotely-triggered earthquakes“ at each end of the magma tunnel. These earthquakes are a sign of stress being released but do not indicate that magma is moving in the areas where they are detected.

The Science Council’s opinion is that the Reykjanes peninsula activity may be expected to come in stages over the coming days. We must assume that if the magma tunnel continues to expand over the coming days and weeks, that we can expect similar earthquake bursts as were detected over the weekend.

These scenarios remain the most likely:

  • Seismic activity will decline over the next few days or weeks.
  • The swarm of earthquakes will increase with larger earthquakes, as high as magnitude 6, in the vicinity of Fagradalsfjall.
  • An earthquake as high as magnitude 6.5 will originate in Brennisteinsfjöll.
  • Magma intrusions continue in the vicinity of Fagradalsfjall:

    • Magma intrusion activity decreases, and the magma solidifies.
    • This will lead to an effusive eruption with a lava flow that is unlikely to threaten inhabited areas.
Þú ert að nota: brimir.rhi.hi.is