May 7, 1959 Tsunami: Northern Norway

Data from Jorstad (1968). Submarine clay slide outside Sokkelvik in the fjord Reisafjorden, Nordreisa, Troms. 3-4 million cubic meters of material located along the shoreline was released and generated one wave propagating mostly outwards into the fjord. Run-up of one small and long wave followed by 2 larger ones of up to 4 m height observed at the head of the fjord. About 2 minutes between first and third wave. Wave noticeable 8 km away. Numerical simulation of submarine slide by Norem et al. (1989), Braend (1961). (reference #11164)

The Sokkelvik landslide and associated tsunami led to nine casualties and is considered one of the most devastating Norwegian quick clay landslide of the past century. In this paper we review the potential causes for this landslide based on an integrated study of eye witness testimony, swath bathymetry data and stability analyses. Results show that the Sokkelvik landslide was most likely triggered by intense rainfall and snowmelt, but that the main cause is associated to the load of an up to 7.5 m high embankment fill. This fill was placed at the shoreline for road construction 6 months before the landslide. Results presented herein show the importance of accounting for extreme rainfall events and groundwater flow when planning construction activity in sensitive near shore areas. (reference #11863)

Seventeen people were caught in the slide and of these 9 lost their lives. It is not clear whether this slide started as an underwater slide (flow slide?) further out in the fjord and progressed towards the shore, or whether it started at the shore and progressed outwards [...] 4 m high flood waves developed which were noticeable up to 8 km from the slide area, as shown in Fig. 5. An eye witness at Sokkelvik said that after he saw the slide started a wave developed and travelled out into the fjord. This wave was more noticeable as it went out into the fjord than when it travelled towards the head of the fjord. At the head a train of 3 waves was observed, consisting of a small wave followed by 2 larger ones. One eye witness said that the first wave he saw was very long, and this is highly unusual. An estimated l minutes elapsed between the first and the third wave. As the second wave moved out from the shore, the sea dropped to a level lower than at any time before. After the 3 waves were observed the sea continued to "pull up" to a level 1. m below normal low tide. (reference #13255)