T-Phases Observed At The Ionian Seafloor: Seismic Source And Bathymetric Effects

T-waves are acoustic waves generated by earthquakes at the land-water interface. They can propagate efficiently for thousands of kilometers within the ocean's low-velocity waveguide-the SOund Fixing And Ranging (SOFAR) channel. In the present work, we studied T-waves that propagate in the Ionian basin and are generated by regional earthquakes (epicentral distance <1000 km) located in the Hellenic Arc (Greece). The Ionian Sea is a small basin that has strong bathymetric variations and is limited at its western edge by a steep continental slope-the Malta escarpment. T-waves from Greece were recorded by a broadband seismometer onboard one of seafloor-observing units of the Western Ionian Regional Facility of EMSO-European Multidisciplinary Seafloor and water column Observatory Research Infrastructure (see Data and Resources) deployed in the western Ionian Sea (Italy) at about 2100 m water depth. By studying the particle motion and T-phase energy flux (TPEF) of the T-waves recorded at the observatory, we find that the western Ionian Sea bathymetry is an efficient reflector for T-waves within the SOFAR channel. To investigate whether factors other than T-wave path effects drive TPEF levels, we also study the source part of the T-wave generation process.