Within the collaboration project NICE (North ICeland Experiment), the german part TJOSTE 2004 (DFG-project RI1220/2-1) was funded between 2004 and 2006 following a bundle application on plume-ridge interaction in Iceland. We cooperated closely with our other partners in the german bundle project (University of Frankfurt, GEOMAR, University of Kiel etc.) and with our international partners: Vedurstofa Islands (Ragnar Stefanson), ISOR (Bjarni Richter), the University of Iceland (Bryndis Brandsdottir) and the University of Uppsala (Ari Tryggvason).
A set of 14 ocean bottom seismometer stations was deployed in the Tjörnes Fracture Zone north of Iceland between the 28/06/04 and the 04/07/04 by the crew of the R/V Dröfn and a scientific crew from the University of Hamburg (Martin Hensch, Michael Schnese, Marcus Thölen, Rolf Herber) led by investigator C. Riedel.
This was the last cruise of the R/V Dröfn from the Icelandic Marine Research Institute. The sky mostly was a brilliant blue, the crew was very motivated and despite sea sickness the deployment went very well. Two types of instruments were used: on the one hand the Hamburg University Ocean Bottom Hydrophone (HUOB) at 4 positions, on the other hand the GeoPro Double Bowl Ocean Bottom Seismometer at 10 positions. The HUOB are broadband sensors registering one channel at 50 Hz, while the GeoPro stations are short period stations registering 4 channels at 125 Hz.
All instruments were deployed using a crane at the rear end of the ship.
After the deployment was successful, active sources (explosions) were used to gain insight into the underground structures and to allow an accurate locating of the 14 "free fall" OBSes. We know the position where we deploy it from the shipside, but we do not know exactly where it will land without these surveys. The dynamite explosions are the common active source in Iceland, because large compressors to use airguns are not easily accessible. The shots look spectacular.
In September 2004 the stations were recovered using the Arni Fridriksson, the biggest ship of the icelandic research organization. During this cruise we also recovered the island station on Lagey from the temporary land network that was mainly run by our swedish research partners. Our icelandic partners on board the ship used the cruise to extend the multibeam bathymetry coverage inside the crater of Storagrunn submarine volcano and along the southermost part of Kolbeinsey Ridge
First results were published in Marine Geophysical Researches, work on a local earthquake tomography is still in progress and work on the multibeam data is waiting to be started.
C. Riedel, A. Tryggvason, T. Dahm, R. Stefanson, R. Bödvarson, G. Gudmundsson (2005) The seismic velocity structure north of Iceland from joint inversion of local earthquake data, Journal of Seismology, Vol. 9, No. 4, 383-404
C. Riedel et al., The NICE group (2006) First results of the North Iceland Experiment (NICE), Mar. Geophys Res.
M. Hensch, C. Riedel, J. Reinhardt, The NICE group Hypocenter migration of fluid induced earthquake swarms in the Tjörnes Fracture Zone (North Iceland), Tectonophysics, 447, 80-94
1. Last cruise of Dröfn in June/July 2004, Deployment of OBSes.
2. Cruise A13/2004 of Arni Fridriksson in September 2004, Recovery of OBSes, Multibeam bathymetry