A review of approaches for submarine landslide-tsunami hazard identification and assessment

Submarine landslides can generate destructive tsunamis. Yet their recurrence intervals and tsunamigenic mechanisms are poorly understood, hampering quantification of global exposure and risk. With growing coastal populations and climatic changes, the impacts of tsunami hazards will increase, and will disproportionately affect peoples in underdeveloped countries (e.g., Small Island Developing States). Specific hazard characteristics of submarine landslide-tsunami include the potential for: short tsunami travel times, highly directional waves, locally extreme wave amplitudes and lack of forewarning. Probabilistic tsunami hazard assessments (PTHA) have emerged as the gold standard for tsunami hazard quantification, enabling science understanding to be translated into policy and decision making. However, our knowledge gaps and research challenges largely prohibit PTHA for submarine landslide sources. In this review, we reference Aotearoa New Zealand, as a western Pacific Island nation vulnerable to tsunami hazards, to illustrate the fragmentary nature of the evidence for, and perceived threat of submarine landslide-tsunami typical of many regions globally. We present an overview of geoscience approaches for the identification and assessment of submarine landslide-tsunami hazards, which include construction of submarine landslide databases, source-specific numerical tsunami simulations, successful approaches to submarine landslide-specific PTHA, submarine landslide susceptibility mapping and emerging data science techniques. We recommend a sequence of logical and accessible steps for enhanced submarine landslide identification and hazard assessment aimed at geoscience disciplines. Our recommendations promote strategic approaches to future data collection and enhanced multi-disciplinary collaboration between marine geoscientists, and tsunami, hydrodynamic, hazard and risk specialists.