Earthquake in Brennisteinsfjöll – Faster Subsidence in Krýsuvík and Continued Magma Accumulation at Svartsengi
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Potential for larger earthquakes in Brennisteinsfjöll
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Deformation detected in the Krýsuvík area
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Ongoing uplift at Svartsengi
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Hazard map updated
An earthquake measuring magnitude 3.2 struck southwest Iceland shortly after 18:00 yesterday and was felt in the capital area. The quake was located in Brennisteinsfjöll, an active seismic zone. Since the onset of activity on the Reykjanes Peninsula in 2020, seismicity in this area has increased, reflecting growing stress accumulation in the crust.
It should be noted that strong earthquakes recur in this region, although at long intervals, and it is uncertain when the next might occur. The last major events were M6.4 in 1929 and M6.1 in 1968. Since then, building standards have steadily improved with stricter requirements for earthquake-resistant design. While earthquakes of this size can trigger rockfalls in steep slopes and cause household items to shift, injuries in Iceland are rare and most often result from unsecured objects falling during shaking.
In earthquake-prone areas it is advisable to take preventive measures to reduce the risk of damage, such as securing heavy objects so they are not placed above beds, and reviewing guidelines on how to respond during earthquakes.
The epicenter of yesterday's earthquake in Brennisteinsfjöll. It measured M3.2 and was widely felt in the capital area.
Some seismic activity has also been recorded west of Kleifarvatn. Krýsuvík and nearby areas are historically known for earthquakes, but recent activity is mainly linked to intrusion-related quakes beneath Fagradalsfjall and Sundhnúkur. At Krýsuvík, both uplift and subsidence have been measured. The area has shown such fluctuations before, but the current deformation appears faster than previously observed. Further analysis is underway.
Experts are closely monitoring the situation, assessing data daily and communicating findings as needed.
Magma accumulation continues beneath Svartsengi at a rate similar to that before the last eruption. No seismic activity has been detected in the area since the eruption began.
Ground deformation
The figure shows vertical ground motion in Krýsuvík measured by the KRIV GPS station since 2020. In the first years, the land rose steadily, but since autumn 2023 it has been subsiding. Following the eruption at Svartsengi in July 2023, the subsidence has accelerated.
The record also shows regular fluctuations linked to magma movement underground. Since last summer, the subsidence has coincided with increased seismicity in the area, which is a normal response when magma shifts in the crust and redistributes stress.
For comparison, InSAR satellite images are used to measure small surface changes by comparing images taken at different times. These confirm the same pattern as the GPS measurements.
The hazard map for the area has been updated and is valid until 2 September unless conditions change. The main update is that the new lava field has been downgraded to the “some hazard” category (yellow), the same as older lava fields.
