Shunsuke Takemura
1ERI UTokyo
Takemura, S. Characteristics of T-wave generation around submarine volcanoes. Earth Planets Space 77, 150 (2025). https://doi.org/10.1186/s40623-025-02284-9
Unexpected major tsunamis have occurred at Sumisu Caldera with an interval of about 10 years. Recently, a similar unexpected major tsunami from Sofu Seamount was reported. Sumisu Caldera and Sofu Seamount are submarine volcanoes far south of Japan. Large T waves from the accompanying seismic events were observed during these tsunamigenic events. Characteristics of T waves could be useful as monitoring metrics for seismicity and tsunami excitation at submarine volcanoes. To understand T-wave generation around submarine volcanoes, I conducted numerical simulations of seismic-acoustic wave propagation from regions around Sumisu Caldera and Sofu Seamount and evaluated T-wave characteristics at various source locations. For sources just below the seafloor, efficient T waves are generated in wider areas of the simulation regions. As depth below the seafloor increases, epicenters with large-amplitude and short-duration T waves are concentrated within the submarine volcanoes of Sumisu Caldera, Sofu Seamount, and Sofugan Volcano. Exampled seismogram envelopes of T waves are illustrated in Figure 1. Large-amplitude and short-duration T waves at a certain seismic station are generated from the seismic source located near the steep (> 10º) downslopes oriented toward the seismic station. Large-amplitude and short-duration T waves from regions far from steep downslopes oriented toward the seismic station could not be observed at the station. Both slope angle and downslope direction are important for T-wave generation. The heterogeneous variation of downslopes at submarine volcanoes also causes anisotropic azimuthal patterns of T waves at far stations. The heterogeneities of bathymetric features around source regions cause variability of T-wave characteristics, and consequently, horizontal and vertical locations of seismic events could be constrained by not only body and T-wave travel times, but also T-wave characteristics.
