Observation and modeling of the seismic seiches triggered in the Gulf of Corinth (Greece) by the 2011 Mw 9.0 Tohoku earthquake

The study reports an unusual water level rise in the Gulf of Corinth, central Greece, during the passing of the seismic waves of the remote 2011 Mw 9.0 Tohoku earthquake. The seismic seiches were recorded by a tide-gauge located in the marina of the island of Trizonia, in the western side of the gulf. The cross-analysis between the ground motion and the water level changes shows that seiching was initiated by the arrival of the earlier S-waves and then enhanced by the surface waves. The seiching concerns five domains with periods ranging from minute to about 7 min and with water level changes of a few millimeters to a few centimeters. The main seiching period is about 5-7 min and the related water level has a maximum trough-to-peak amplitude of about 6-8 cm. Numerical simulation of the seismic seiches, based on the shallow water equations, allows us to model reasonably well the amplitude of the seiches for most of the period domains, excepted those for the main seiching period at 7 min, which are underestimated by a factor of about 2-3. The largest bathymetric structures of the gulf to be excited in a seiche mode, with eigenperiods of hundreds of seconds, are a few kilometers in size.