The seismotectonic signi"cance of the Rana region is known both from the fact that this was the location of the largest known
earthquake in Fennoscandia in recent times, the MS 5.8}6.2 earthquake of August 31, 1819, and from its relatively high, constant
seismic activity also in the 20th century. In order to study this region in more detail, a local seismic network has been in operation
there since July 1997, as part of the NEONOR (Neotectonics in Norway) project. The network was primarily designed to detect
possible activity on the Ba>smoen fault which runs&50 km subparallel to the Rana fjord, and which shows signs of likely post glacial
activity. The results have revealed a quite complex spatio-temporal distribution of seismic activity, and has also shown no activity on
the Ba>smoen fault itself. During the "rst 18 months of operation (July 1997}January 1999), the network has detected 373 locatable
seismic events, of which 267 were local earthquakes. Most of these earthquakes occurred in "ve groups in the western parts of the
network. All "ve groups had similar NNW-ESW trends in epicenter locations, and all have shallow foci (2}12 km), similar to what has
also been found earlier for other concentrated earthquake zones in Northern Norway, and the magnitude range is between ML 0.1 and
2.8. Earthquake focal mechanism solutions within the network reveal a predominance for normal faulting with the tensional stress
axis perpendicular do the coastline (implying an unusual coast-parallel orientation of the principal horizontal compressive stress). The
earthquakes occur in a region of maximum post-glacial uplift gradients, which supports deglaciation #exure as a viable explanation
for these earthquakes. A certain in#uence from more local factors, however, tied in general to crustal in homogeneities, cannot be
ruled out.