The February 23, 1887 tsunami recorded on the Ligurian coast, western Mediterranean

The catastrophic Ligurian Earthquake on February 23, 1887 caused significant damage and numerous casualties in northwestern Italy and southeastern France. The first (main) shock (estimated magnitude of 6.2-6.5) produced tsunami waves observed along 250 km of the Ligurian coast from Genoa to Cannes. Typical tsunami run-up heights were 1-2 m. The first wave was found to be negative, supporting the assumption that the earthquake was produced by release of stress along an offshore normal fault. Computed tsunami waveforms are in qualitative agreement with observed run-ups. Unique 1887 tsunami records in Genoa and Nice harbors were found and analyzed. Numerical computations of eigenoscillations for the old (1887) Genoa harbor were made and found to be in a good agreement with the tsunami observations. The dominant observed period of 22.5 min was shown to be related to the fundamental (Helmholtz) mode of the old port. Long ''ringing'' and slow decay of tsunami oscillations in Genoa are associated with ''pumping'' of wave energy from the external basin. Several wave trains are revealed in the record that occur at 2 - 2.5 h intervals. They are interpreted as edge waves propagating along the Ligurian shelf and reflecting from its borders.