Gravity and height variations during the present rifting episode in Northern Iceland

In 1975, a rifting episode started in the neovolcanic zone of northern Iceland, consisting of a succession of slow inflation periods and rapid subsidence events, which is still going on. The center of activity is situated below the Krafla caldera, and the rifting process is affecting the 80-km-long fissure swarm associated with this central volcano. Gravity and height variations associated with this process have been investigated by re-observing profiles earlier established in the Namafjall and in the Gjastikki area, situated nearly 10 km south and north of Krafla respectively, as well as by the re-observation of a number of gravity stations in the northern part of the fissure zone, in 1976, 1977, and 1978. By repeated observations with 2 or 3 LaCoste-Romberg gravity meters, the accuracy obtained in each gravity survey is of the order of ± 10 x 10-8 ms-2. In the profiles crossing the fissure zones, a rate of gravity increase of more than 100 x 10-8 ms-2/a has been found in the central part, while gravity at the flanks decreases at the same order. These variations are correlated with subsidence and elevation rates of the order of 0.5 m/a.           ARK: https://n2t.net/ark:/88439/y060150 Permalink: https://geophysicsjournal.com/article/268 &nbsp