Tsunami taxonomy and detection from recent Mediterranean tide gauge data

Sea level records, collected in digital form with high sampling rate by recently upgraded tide gauges located along the Mediterranean coasts, are subjected to a posteriori investigation to examine and characterize occurrence of sea level oscillations in the tsunami period range, induced by both underwater or coastal earthquakes and by meteorological events. After performing a rigorous quality control procedure on the raw sea level time series, a wavelet based analysis is applied to 2 h high-pass filtered data to identify oscillations generated by earthquakes, and a few events are modeled aiming to verify travel time and expected spectral shape. Seismic tsunami oscillations that are not reported in published catalogues are identified in the sea level records of the period 2010-2014 just after three different earthquake events. A method is proposed to detect occurrence of tsunami-like oscillations of meteorological origin from the available tidal records based on the distribution of the detided level process over spectral bandwidth parameter and mean period. The developed methodology is also the first presented which allows to distinguish sea wave induced harbor seiches from fluctuations of meteorological origin associated with passage of atmospheric disturbances (meteotsunamis) in sea level time series. The results of the analyses show that, during the considered period, in the Mediterranean Sea tsunamis of seismic origin are rare and weak; meteotsunamis on the contrary are relatively frequent and in critical areas may reach intensities exceeding astronomical tide. The availability of the recently acquired high frequency records and the presented approach allow to extend the list of recorded tsunami events of both seismic and meteorological origin. The identified event sets may be used for improved hazard analyses and risk assessments along the Mediterranean coasts.