Hydrothermal fluid flow triggered by an earthquake in Iceland

Microearthquake hypocenters were analyzed in the Krýsuvík geothermal area in SW-Iceland with data taken from two consecutive passive seismic surveys, 2005 and 2009. Five years prior to the 2005 survey, this area was struck by an earthquake initiating a major top-to-bottom fluid migration in the upper crust. The surveys reveal a complex bottom-to-top migration of seismicity with time following this fluid penetration, suggesting the migration of a pore pressure front controlled by the upper-crust fracture system. This is interpreted as the time and space development of high-temperature hydrothermal cells from a deep upper crustal fluid reservoir in the supercritical field. These results provide insight into the coupling mechanisms between active tectonics and fluid flow in upper-crustal extensional systems with high thermal flux.

Laurent Geoffroy, Catherine Dorbath, Kristján Ágústsson, Sigríður Kristjánsdóttir, Ólafur G. Flóvenz, Cécile Doubre, Ólafur Gudmundsson, Thibaut Barreyre, Sara Bazin, Aurore Franco