Reykjanes Seismic Activity: Tremor Pulse Detected, Surges Might Continue Skip to content

Reykjanes Seismic Activity: Tremor Pulse Detected, Surges Might Continue

By Gréta Sigríður Einarsdóttir

Photo: Golli.

A tremor pulse and increased seismic activity were detected by Fagradalsfjall shortly after 5.00am this morning. While an eruption is still one of the four possible scenarios, new data suggests the magma flow is slowing down. The activity occurred in the southernmost part of the magma passage and if the movement continues, earthquake streaks such as the one occurring last weekend might continue as well.

Recent activity

Around 5.20am this morning, increased seismic activity was detected at the southernmost part of the magma passage underneath Fagradalsfjall. A tremor pulse was detected around the same time and lasted until around 7.00am. This likely means the magma passage is growing. Since then, there’s been a steady activity of smaller quakes.

The latest satellite images, GPS measurements, and models all indicate that the magma flow has decreased since the beginning of last week. Still, the magma is close to the surface and we must continue to assume that an eruption might occur. If the magma passage continues to grow in the next few days and weeks, we might also expect similar earthquake surges to the one over the weekend, which was powerful enough to unsettle the residents of Grindavík.

Map of the Reykjanes Peninsula indicating the magma intrusion and the areas at each end where seismic activity due to tension release might occur.
Icelandic Met Office. The red line marks the magma intrusion underneath the area between Fagradalsfjall and Keilir. The grey areas indicate where earthquakes due to tension release might occur.

Magma intrusion affects surrounding area

When magma flows into the ground’s surface, creating a magma intrusion, it creates tension in the earth’s crust. This leads to increased tension in large areas around the magma intrusion, which can trigger earthquakes in areas at either end of the passage (grey areas on the map). When such earthquakes occur, it’s a sign of tension release in the ground underneath, not magma movement.

It is still the consensus of the Scientific Advisory Board that if an eruption occurs, a fissure will open somewhere in the area between Fagradalsfjall and Keilir where the magma passage is forming. There are no indications of magma movement outside this area. The most likely point of eruption, considering the activity in the past few days, is in the southernmost part of that passage, by Fagradalsfjall.

Possible scenarios

Experts still assume that one of the four scenarios is the most likely:

  • The seismic activity will die down in the coming days or weeks
  • The activity will increase with larger quakes, up to M6 by Fagradalsfjall
  • An earthquake of up to M6.5 will originate in Brennisteinsfjöll.
  • The magma intrusion at Fagradalsfjall continues, leading to
    • Magma flow dying down and the magma cooling and hardening
    • A fissure eruption and lava flow that likely won’t threaten inhabited areas

The Brennisteinsfjöll mountains are situated closer to Reykjavík than Fagradalsfjall and a large earthquake originating there would affect the capital area.

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