Figure3 The ocean area monitored by the hydroacoustic station located at Crozet Island is shown in white.
T-PHASE STATION
Underwater seismic events couple seismic into acoustic energy at the interface between the sea bed and the water. Some of this acoustic energy becomes trapped in the SOFAR channel and travels long distances. These waves are known to the seismic community as T-phases (tertiary phases). The essential character of these signals is that the majority of the propagation path has been through the ocean. For many years, island or coastal seismograph stations have recorded numerous such signals. These signals have primarily come from undersea events such us earthquakes or underwater volcanic activity.
The T-phase station of the IMS uses a seismometer on a small island to detect signals that have propagated largely through the ocean.
A good understanding of seismic/acoustic conversion process at the flank of the island will enable improved localization and identification of underwater seismic events. This is an area of increasing research activity. The bathymetry features of the ocean floor, such as cliffs and slopes play an important role in the coupling processes.
