Summary
The Ranafjorden area in northern Norway is a region of increased seismicity and
anomalous land uplift. There is evidence for recent movements in the bedrock;
1) A total of 0.89 m uplift of a bladder wrack mark from 1894 to 1990 in
Hemnesberget; 2) Anomalous low uplift of the islands of Hugla and Tomma in the
outer Ranafjorden area (0,0 0.06 and 0.07 m from 1894 to 1990 compared to 0.25-
0.30 m in the area to the north and the south); 3) Associated with the 1819
magnitude 5.8-6.2 earthquake in the Ranafjorden area, an uplift of a shallow
sea floor above sea level during an aftershock was reported in the bay Ut-
skarpen. During the main earthquake a major land slide occurred at the same
location. This earthquake is the largest North European near-shore earthquake
recorded in historical time; 4) An uplift of approximately 1 metre of a farm-
house in the 1870's at Båsmoen. The observation has been made relative to the
two neighbouring mountains Snøfjellet and Høgtuva. 5) Approximately 0.5 m
uplift of a boathouse in the bay Straumbotn during the last 50 years.
There are, consequently, indications of recent faulting in the Ranafjorden area
It is, however, difficult to find conclusive evidence for postglacial and
present-day movements along specific faults. We have therefore established
a Global Positioning System (GPS) network designed to measure the active
geological strain in the area.
