Tempo and triggering of large submarine landslides: Statistical analysis for hazard assessment

Abstract

Due to their potential volume and speed, large submarine landslides can generate destructive tsunamis or damage expensive seafloor structures. Understanding their timing is therefore important for hazard assessments; however, dating large numbers of landslides close to their origin is logistically difficult. Previous landslide studies are typically limited to fewer than ten observations of ages. To address this we analyse extensive, continuous and long-term turbidite records from four deep-sea basins which are interpreted to be the distal deposits of large, disintegrative landslides. Our records include sufficient numbers of turbidites (N=151–1571) for robust statistical analysis of long-term controls on event timing and testing for relationships with triggering mechanisms such as earthquakes, sea level, climate change and volcanic activity. We explore statistical methods developed by medical, economic and biological disciplines and show how they can be applied to analysis of submarine landslide frequency and triggering. Frequency analysis of field data reveals two different distribution forms for landslide recurrence – exponential and log-normal. We discuss possible individual and combined effects of controlling factors that result in these distributions. Rescaled range and Gaussian finite mixture models determine whether and how landslides are clustered in time. Parametric Generalised Linear Models and non-parametric Proportional Hazards Models are used to test for the significance and influence of different variables and their rate of change. We demonstrate the value of unusually detailed long-term landslide records, and show how statistical analysis provides quantitative inputs for future hazard assessments, landslide-climate studies and understanding the tempo of deep-sea sediment flux.