The 1956 Greek tsunami recorded at Yafo, Israel, and its numerical modeling

A record of a tsunami event riding on the usual tide signal was recorded by a floating-type tidal gauge installed in the port of Yafo, Israel. The tsunami was triggered by an earthquake in the Aegean Sea on 9 July 1956. This paper presents a retrieval of tsunami waves from the record. At the first stage of the study an attempt had been undertaken to reproduce the 1956 tsunami assuming a coseismic nature of its generation source. Although these simulations resulted in tsunami waves with their amplitude close to that obtained from the record measured at Yafo, they did not contain significant spectral energy components with periods of similar to 15 min as appear in the spectra of 1956 tide-gauge records. When landslide movement, triggered by the main shock and/or by the largest aftershock, is suggested as a source of these tsunami waves, the spectra of the resulted marigram obtained in the proximity to Yafo contain harmonics with frequencies very close to those measured. This corroborates the landslide nature of the tsunamigenic source responsible for generation of higher-frequency ( relative to the tidal waves) energy components. The peak periods determined via spectral analysis of the recent tide-gauge records ( 1 year and longer) in the absence of tsunami events vary from 50 to 60 min. Similar periods have been revealed in a special numerical study dealing with longwave propagation toward the coast of Israel, thus confirming that their origin is related to continental shelf resonance. These resonance periods differ significantly from those found for the 1956 tsunami.