T-Phases Observed at the Ionian Seafloor: Seismic Source and Bathymetric Effects

Abstract

AbstractT-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.