Development of Probabilistic Methods to Assess Meteotsunami Hazards

Wednesday, 17 December 2014: 12:05 PM
Uri S Ten Brink, US Geological Survey, Woods Hole, MA, United States and Eric L Geist, USGS Pacific Coastal and Marine Science Center, Menlo Park, CA, United States
A probabilistic method to assess the hazard from meteotsunamis is developed from both probabilistic tsunami hazard analysis (PTHA) and probabilistic storm-surge forecasting. Meteotsunamis are unusual sea level events, generated when the speed of an atmospheric pressure or wind disturbance is comparable to the phase speed of long waves in the ocean. A general aggregation equation, similar to that used in PTHA, incorporates different meteotsunami sources. A historical record of 116 pressure disturbances recorded between 2000 and 2013 by the U.S. Automated Surface Observing Stations (ASOS) along the U.S. East Coast is used to establish a continuous analytic distribution of each source parameter as well as the overall Poisson rate of occurrence. Initially, atmospheric parameters are considered independently such that the joint probability distribution is given by the product of each marginal distribution. The probabilistic equations are implemented using a Monte Carlo scheme, where a synthetic catalog of pressure disturbances is compiled by sampling the parameter distributions. For each entry in the catalog, ocean wave amplitudes are computed using a finite-difference hydrodynamic model that solves for the linearized long-wave equations. Aggregation of the results from the Monte Carlo scheme results in a meteotsunami hazard curve that plots the annualized rate of exceedance with respect to maximum event amplitude for a particular location along the coast. Results from using 20 synthetic catalogs of 116 events each, resampled from the parent parameter distributions, yield mean and quantile hazard curves. An example is presented for four Mid-Atlantic sites using ASOS data in which only atmospheric pressure disturbances from squall lines and derechos are considered. Results indicate that site-to-site variations among meteotsunami hazard curves are related to the geometry and width of the adjacent continental shelf. The new hazard analysis of meteotsunamis is important for a comprehensive assessment of coastal hazards associated with long-period ocean waves.