The Torfajökull volcanic system is one of about thirty active volcanic systems in the neovolcanic zones of Iceland.
Eruptions of the Torfajökull are highly explosive, hence, the volcano represents a significant volcanic hazard for
the whole North Atlantic region. In active volcanic areas low-velocity zones are expected, indicating the presence
of fluids and relative high temperatures. Using natural occuring seismicity, the size and properties of anomalous
crustal velocity structures can be mapped by inverting for the 3D velocity structure. To illuminate the internal
crustal structure of Torfajökull, I propose a tomographic study on active and passive seismicity around the volcanic
area. A passive seismic data set has been recorded recently in this area. First investigations indicate, that there is
high-quality P- and S- wave local earthquake data for a 3D tomographic experiment. By including readings from
surrounding permanent stations, explosions, and selected regional events the ray coverage in the subsequent process
will be improved. In a first step local earthquakes will be relocated, since high-precision earthquakes locations are
needed for the inversion. In the inversion process, manually picked seismic travel times will be inverted
simultaneously for hypocenter and seismic velocities. This will yield a more detailed image of the internal structure
of the Torfajökull volcanic area, and give information on location and size of low-velocity areas. In the following
interpretation of results, high-precision earthquake relocations will be included to map possible thrusts and weak
zones within the crust. The results of this project will give important information for the assesment of earthquake
and volcanic hazard in the hazardous area. Reliable velocity models are also essential for other gephysical
investigations (e.g. GPS and Gravimetry).