The Iceland Met Office website has a status page at https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night
It has mentioned using models to determine the location and size of the magma body which is threatening to erupt in the vicinity of Grindavík and the Blue Lagoon. They have also published estimates for the inflow rate of new magma into the linear chamber.
How do they determine these things? What data are the estimates based upon? How confident are geologists in the model outputs?