Signatures of Krakatau Tsunami Recorded by Tide Gauges along the European Atlantic Coast

The explosion of Krakatau volcano in 1883 generated one of the highest tsunami ever recorded by tide-gauges. In the North Atlantic, the only known tide gauges that have recorded the Krakatau tsunami are situated along the coast of France and UK. These records have been collected and reproduced by Symons (1888), but the reproductions are not of very high quality (Pelinovsky et al. 2005). As the Krakatau tsunami height is rather small in the North Atlantic (~20cm), it is often difficult to isolate the sea level oscillations due to tsunami from those provoked by high frequency tidal constituents or by meteorological forcing. In this report, we re-analyze the Krakatau tsunami signal at the North Atlantic European tide-gauges by replacing some of Symons' data by the digitized original sea level records and by adding a few new records that have been discovered recently in the archives. The theoretical tsunami arrival time has been estimated by the ray-tracing method. A wavelet decomposition has been applied to identify the tsunami wave and to isolate it from tidal and meteorological sea-level oscillations. The results of wavelet analysis have been validated at Rochefort (France) by comparing them with the predictions of a high resolution local tide-surge model available for this area.