Multilayer modelling of waves generated by explosive subaqueous volcanism

Abstract

Abstract. Theoretical source models of underwater explosions are often applied in studying tsunami hazards associated with subaqueous volcanism; however, their use in numerical codes based on the shallow water equations can neglect the significant dispersion of the generated wavefield. A non-hydrostatic multilayer method is validated against a laboratory-scale experiment of wave generation from instantaneous disturbances and at field-scale subaqueous explosions at Mono Lake, California, utilising the relevant theoretical models. The numerical method accurately reproduces the range of observed wave characteristics for positive disturbances and suggests a relationship of extended initial troughs for negative disturbances at low-dispersivity and high-non-linearity parameters. Satisfactory amplitudes and phase velocities within the initial wave group are found using underwater explosion models at Mono Lake. The scheme is then applied to modelling tsunamis generated by volcanic explosions at Lake Taupō, New Zealand, for a magnitude representing an ejecta volume of 0.1 km3. Waves reach all shores within 15 min with maximum incident crest amplitudes around 0.2 m at shores near the source. This work shows that the multilayer scheme used is computationally efficient and able to capture a wide range of wave characteristics, including dispersive effects, which is necessary when investigating subaqueous explosions. This research therefore provides the foundation for future studies involving a rigorous probabilistic hazard assessment to quantify the risks and relative significance of this tsunami source mechanism.

Scenario–based Modelling of Waves Generated by Sublacustrine Explosive Eruptions at Lake Taupō, New Zealand

“…Mader (2001); Ulvrová et al (2014); Ulvrova et al (2016);Heidarzadeh et al (2020)), which are very frequently used for the efficient solution for seismogenic tsunami magnitudes and travel-times (Popinet, 2011;LeVeque et al, 2011). While these are appropriate when the characteristic wavelength L is larger than the water (or ocean) depth h, a different approach is required where these waves reach shores and other situations where non-linear and non-hydrostatic effects are significant (Esposti Ongaro et al, 2021;Hayward et al, 2022b).…”

“…This semi-analytical method and variants thereof have been used to simulate the 1996 eruption at Karymskoye Lake, Russia, by Torsvik et al (2010); Ulvrová et al (2014), and utilised to investigate submarine eruptions at Kolumbo Volcano (Ulvrová et al, 2014), Taal Caldera Lake, Philippines Pakoksung et al, 2021), and at Campi Flegrei, Italy , all using either SWE or Boussinseq-type equation based methods. For the multilayer scheme, the explosive source model has been tested for waves generated by chemical detonations in Mono Lake, California (Hayward et al, 2022b).…”

“…The numerical scheme is set up for each simulation to model the terrain with a lake level set at 356.9 m, a typical yearly maximum lake level as measured by the operating utility company and a maximum refinement level of 12 resulting in a this being guided by previous numerical work at the lake (Hayward et al, 2022b). No special considerations for domain boundaries are needed as flows do not encroach upon these because of the elevation profile.…”

“…In an effort to capture a wide range of dispersive and non-linear properties of the generated wave-fields, we utilise a non-hydrostatic (NH) multilayer scheme within the Basilisk computational fluid dynamics (CFD) framework introduced by Popinet (2020). This numerical method has been tested and validated against records of waves generated by instantaneous disturbances and explosives at field scale (Hayward et al, 2022b), and in the present work is applied to investigate direct and secondary hazards posed by volcanogenic tsunamis in Lake Taupō in terms of incident wave heights and velocities, inundation, impacts across the built environment on the shore and impacts on infrastructure including tsunami-induced pressures on the Waikato outlet control gates. The aims of this work are to present a detailed case study of volcanic wave hazard from an idealised explosive subaqueous source and, by utilising an appropriate numerical scheme for the types of generated waves and with high resolution digital terrain models (DTM), provide a basis on which future probabilistic hazard and risk assessments can be developed when they take into account all potential volcanic hazard sources.…”

Development of black ice prediction model using GIS-based multi-sensor model validation

“…The GIS is a tool for simulating system dynamics and conducting research on various disasters. Studies using the GIS include ice and snow analysis (Jeong et al, 2019;Koumoutsaris, 2019;Bardou and Delaloye, 2004;Cheng et al, 2007), flood analysis (Wang et al, 2021), underwater volcanic eruption modelling (Hayward et al, 2022), traffic analysis during natural disasters (Toma-Danila et al, 2020), and earthquake and landslide analysis (Yi et al, 2019;Ali et al, 2019), among others. In this study, as well as in predicting and mapping (simulation) black ice, the GIS was applied by referring to previous disaster-related studies.…”