Fig. 1.

Location of the fibre-optic cable in Reykjanes and main geological features⁷⁰. Location of the fibre-optic cable (continuous green line) from the telecommunication network (Míla Company) used for our measurements within the Reykjanes fissure swarm (black lines). Small light blue squares along the fibre-optic cable represent geophones. Blue triangles indicate broadband seismological stations from the European Project IMAGE (Integrated Methods for Advanced Geothermal Exploration) network^41,44. RAH and EIN are the closest broadband stations to the optical cable. The thick black lines indicate a series of cones and postglacial craters, from the latest eruptive episode in Reykjanes in 1210–1240 (e.g. Dyke E = Eldvörp crater row). The black star indicates a local earthquake epicentre (depth ~3.5 km). The thin red curve indicates the limit of the Sh = Sandfellshæð lava shield (most recent lava flow), hiding most of the faults at the surface of the tip of the Peninsula. The inset represents the location of the area in Iceland (North Atlantic), with black dots being epicentres of 68 earthquakes (Supplementary Table 1) recorded during the 9 days of our optical DAS records