Determination of crustal velocity structure around Lake Toba (incl. Sumatra fault) and possibly between Nias Island and the coast using british airgun sources (Pg and Pn phases). This will be the northern extension of the British study area. Study of the Lake Toba caldera and its relation to the Sumatra Fault by analyzing local volcano-related events. Supply of recordings of regional and teleseismic events to partners for joint interpretation. etc.