Clear evidence of uplift in Svartsengi, intense weather impacting seismic monitoring, Iceland

On November 21, 2023, the Icelandic Meteorological Office (IMO) reported a decrease in seismic activity in the Reykjanes Peninsula, with 165 earthquakes, all below magnitude 2, detected since midnight. This decline contrasts with the previous days’ average of 1 500 to 1 800 earthquakes per 24-hour period.

However, experts suggest that the current severe weather conditions across Iceland could be impacting the system’s sensitivity to detect the smallest quakes, making it challenging to assess whether there is a genuine reduction in seismic activity.

One of the most striking observations is the continued land uplift at Svartsengi. Satellite images and GPS data have shown that the land has been rising steadily, a trend that began following the fissure’s formation. The rate of uplift has remained nearly unchanged in the last 24 hours, indicating ongoing subterranean movements. This uplift is consistent with patterns observed when magma accumulates underground, causing the earth’s surface to rise.

“The rapid, ongoing uplift close to Svartsengi is occurring in the same area where uplift was measured before the magma intrusion formed on November 10,” IMO said. “Geodetic models derived from satellite images show that the uplift in Svartsengi area is considerably faster than before.”

“Generally, when a magma intrusion forms, subsidence occurs above the centreline of the intrusion, as seen in Grindavík, with signs of land uplift discernible adjacent to the intrusion. Crustal uplift in the Svartsengi region due to magma accumulating at depth has been measurable since the intrusion began to form on November 10. Initially, the uplift sign was influenced by the formation of the intrusion, but now the dominance of deep magma recharge is apparent.

“The clear sign of crustal uplift in Svartsengi region does not change the likelihood of an eruption from the magma intrusion,” according to IMO. “This is assessed, amongst other things, on the fact that the Earth’s crust over the magma intrusion is much weaker than the crust over the uplift region close to Svartsengi.”

As long as there is not significant seismicity in the Svartsengi region, there is not a high likelihood of an eruption at that location. Moreover, an eruption is still deemed more likely from the intrusion, particularly if there is a sudden, large inflow of magma into the intrusion.

In response to these developments, IMO has updated the hazard maps for the areas around Grindavík and Svartsengi. The revised maps, based on new satellite images and other data, have expanded the designated danger zones. These updates are crucial for the planning and response strategies of the Civil Protection and the Police in the Southern Peninsula Region.

The current weather conditions in Iceland are presenting challenges to the monitoring efforts. Heavy winds and precipitation are expected to reduce the sensitivity of seismic and real-time GPS monitoring systems. Additionally, sea swells are affecting low-frequency measurements in unrest readings, where waves appear as disturbances. Fog and dark squalls also hinder the visual confirmation of any eruptions using cameras.

Despite these challenges, the Icelandic Meteorological Office, along with experts from the University of Iceland, continues to closely monitor the situation. The teams are constantly reassessing and interpreting the incoming data to provide timely updates. The evolving nature of the seismic activity and the land uplift at Svartsengi indicate that the region remains in a state of flux, with the potential for rapid changes.

References:

¹ Clear evidence of uplift in Svartsengi – IMO – November 20 and 21, 2023