Nisyros

Lagios et al. (2002): “After intense seismic activity in 1996, a GPS network was installed in June 1997 and re-occupied annually up to 2002.” Uplift between 14 to 140 mm was measured at all GPS stations. Corresponding horizontal displacements ranged from 13 to 53 mm.The displacement vectors indicate that the island is undergoing extension towards the East, West and South. A two-source “Mogi” model combined with assumed motion along the Mandraki Fault was constructed to fit the observed deformation. The best-fit model assumes sources at a depth of 5500 m NW of the centre of the island and at 6500 m offshore ESE of Yali Island.
Gottsmann et al. (2007) reported joint and simultaneous continuous multiparameter observations at the restless Nisyros caldera, which reveal non-steady short-term oscillatory signals. The combined geodetic, gravimetric, seismic and electromagnetic records indicate that the oscillations are associated with thermohydromechanical disturbances of the hydrothermal system. The dominant period of oscillation (40 – 60 min) indicates short-term processes most likely associated with instabilities in the degassing process. Amplitudes of recorded geodetic and gravimetric signals are comparable to amplitudes observed at other periodically restless calderas. Gottsmann et al. (2007) concludes that shallow aqueous fluid migration can contribute significantly to periodic unrest, explaining the lack of eruptions in many cases of unrest.