Heiti verkefnis : 

Hraðvirk sprungugreining með dróna segulmælingu á hættusvæðum í Svartsengi, Sundhnúkum, Þorbirni og Grindavík

Verkefnastjóri : 

Elisa Piispa

Stutt lýsing á verkefninu:

Widespread tectonic and volcanic activity started in the Reykjanes Peninsula in 2020, after more than 800 years of quiescence. First confined within unhabited areas, the activity switched to the Svartsengi/Grindavik region in October 2023, with large repercussions on the communities and infrastructure. Numerous fissures, fractures, and sinkholes formed, representing danger to workers and inhabitants. These events bearing similarities to past Fires events (Krafla, Reykjanes 800-1200 AD) mean that the activity is likely to continue for years or decades. Rapid fracture surveys to swiftly update hazard maps is therefore needed.

However, detecting the size, shape, orientation and location of the fissures, fractures etc. in areas covered by Holocene lava flows is not easy. We get an idea of the locations and the sense of motion of different units from Insar or Differential DEMs, but the subterranean shape and size of fractures and sinkholes remain elusive. GPR can be effective but suffers from low penetration depth. Our suggested solution is to utilize drone magnetometry to reveal the subsurface structure of these fractures. The main aim of the project is to develop methodology for a rapid response drone magnetometry surveying, that would aid in hazard mapping of underground fractures such as faults and sinkholes related to grabens. Especially, when combining two geophysical methods (GPR data collected by Vegagerðin and magnetometry) with InSAR data, DEMs and existing geological knowledge we will be able to provide a clearer view of the fractures, their locations and sizes, which can be used to assess the hazards related to them.

Tilgangur og markmið:

The purpose of this project is to develop methodology for a rapid response drone magnetometry surveying, to aid in hazard mapping of subsurface structures such as faults and sinkholes related to grabens. The work will concentrate on the recent volcanic unrest area surrounding Grindavik and Svartsengi. The deliverables of the project are likely to have an immediate impact on the vulnerable communities and critical infrastructure in this area.

On 10 November 2023, a significant dyke propagation event originating beneath Svartsengi led to widespread fractures and deformation across the Reykjanes peninsula (Fig.1). This had a severe impact on the town of Grindavík and crucial infrastructure, including the Svartsengi power plant, which supplies electricity and hot water to the capital area and peninsula. The first dyke event, although not leading to an eruption, triggered extensive seismicity, faulting, and the creation of sinkholes. It culminated in the formation of a large graben (1.5km in width), cutting through western Grindavík from the coast to Sundhnúkurgígar, totalling 16km in length. The second dyking event on 14 January 2024, sourced from the same magma storage zone below Svartsengi, resulted in a second graben formation (700m wide) and associated sinkholes in eastern Grindavík (Fig.1). Both grabens utilized pre-existing fault structures which cover the majority of the town. The people of Grindavik are still experiencing the devastating impacts of these graben formations. The underground risks, such as sinkholes or significant fractures within the town, are challenging to evaluate because human-made surfaces often conceal what is beneath, making it difficult to identify and address the hazards.

Remote sensing data, including InSAR (VÍ & Ducrocq et al. 2024), has played a crucial role in locating faults in the region. It revealed that these faults, although often obscured by Holocene lava flows, are very widespread within the Reykjanes Peninsula (Fig. 2). Previously unknown faults, not activated by activity at Fagradalsfjall, have been detected in 2023-24 InSAR data, as well as large movements on known faults. However, the subsurface shape, size, orientation and location of these fractures, especially the largest ones associated with life threatening hazard, cannot be determined solely from satellite data. Moreover, experts from VÍ and HÍ suggest that this event bears resemblance to the historic Krafla Fires and Reykjanes Fires. In both cases the activity persisted for an extended period, spanning longer than a decade. During these periods of distinct inflation and subsequent dyke propagation, the location of unrest migrated within the volcanic systems. It is possible that history will repeat itself, and the current period of unrest on Reykjanes peninsula will continue for a long time, further impacting populated areas and infrastructure. It is therefore crucial to be able to rapidly assess the subsurface conditions of the faults and cavities.