Seismic detection of island trapped sea waves from a landslide-generated tsunami at Stromboli (Italy)

We analyzed short period seismograms recorded at Stromboli, searching for a possible signature of the tsunami following the two landslides occurred on the island on 30 December 2002. By taking advantage of their close occurrence in space and time, we recognized the seismic mark of clock- and counterclockwise tsunami waves trapped by the island coast. The most energetic direct arrivals, running around the island in the two opposite directions, traveled with an average velocity of about 12 m/s, while the waves that traveled more than once around the island display a slightly higher velocity. These observations represent the first instrumental evidence of trapped waves around pseudo-conical islands and demonstrate the possibility of using coastal seismic stations for monitoring tsunami propagation. Our results provide important constraints for early warning of tsunami generated at Stromboli in the Sciara del Fuoco area, where considerable landslides are known to have occurred in the past.