Tracing the sources of paleotsunamis using Bayesian frameworks

Paleotsunami deposits provide a compelling record of these events, including valuable insights into their recurrence and associated magnitudes. However, precisely determining the sources of these sedimentary evidence remains challenging due to the complex interplay between hydrodynamic and geological phenomena and the intricacy of the processes responsible for forming and preserving tsunami deposits. Here, we introduce a novel approach that employs Bayesian inference methods to divide the complex tsunami process into segments and independently handle uncertainties, thereby enabling more precise and comprehensive modelling of the sources. We provide a list of potential earthquake scenarios with different likelihoods instead of a single best fit. Based on this method, we calculated that the source of the 869 Jogan earthquake had a magnitude ranging from Moment Magnitude 8.84 to 9.1 (within one standard deviation) with different slip distributions along the Japan Trench. Our results reaffirm that the Jogan event had a similar order of magnitude to the 2011 Tohoku-oki tsunami and enhanced the applicability of paleotsunami deposits to hazard assessment. Bayesian inference methods can be used to understand the sources of palaeotsunami deposits by recovering the causal source and accounting for uncertainty at each step of the process.