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

Abstract

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 broad band seismometer on-board of one of seafloor observing unit of the Western Ionian Regional Facility of EMSO- European Research Infrastructure (www.emso.eu) deployed in the western Ionian Sea (Italy) at about 2100 m water depth. By studying the particle motion and 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-phases within the SOFAR channel. To investigate if factors other than T-wave path effects drive TPEF levels, we also study the source part of the T-wave generation process.