Three-dimensional submarine-volcano-generated tsunamis: Numerical and physical model comparisons

A recent submarine volcanic eruption in Tonga renewed interest in the dynamics and impacts of tsunamis generated by volcanic activity. Laboratory experiments were performed to investigate tsunami generation by sudden vertical deformation using a novel pneumatic Volcanic Tsunami Generator (VTG), which rapidly displaces a 1.2 m-diameter water column by up to 0.3 m in under one second. Eight representative VTG runs, spanning water depths of 0.9–1.2 m and piston pressures of 40–145 psi, were instrumented with four wave gauges. Three-dimensional simulations solving the full Navier–Stokes equations (TSUNAMI3D) were performed and validated against the experimental data in the time, frequency, and time–frequency (wavelet) domains. Across all gauge locations and cases, correlation coefficients exceeded 84% (up to 96% in the far field) and RMSE remained within 20% of the peak wave heights, demonstrating that TSUNAMI3D reliably captures low-frequency dispersion and transient nonlinearity. Because the VTG imposes rapid vertical volume expansion with a time-varying wetted area, this source-specific validation addresses eruption-analog forcing rather than idealized bottom uplifts. While TSUNAMI3D captures the overall wave dynamics well, near-field nonlinear and multiphase effects remain underresolved; future work should refine grid resolution and free-surface treatment to better capture high-frequency, source-proximal behavior. A validated submarine volcanic tsunami numerical model can support agencies such as the National Tsunami Hazard Mitigation Program in refining inundation and evacuation mapping, thereby enhancing community preparedness and safeguarding lives and property.