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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS002 Oral Presentation 1771
Standards and benchmarks for tsunami modeling
Prof. Utku Kanoglu
Department of Engineering Sciences Middle East Technical University IASPEI
Costas Synolakis, Eddie Bernard, Vasily Titov, Frank Gonzlez
A substantial number of new tsunami codes, more than 20 by some accounts, have been employed in
the aftermath of the December 26, 2004 Boxing Day tsunami. Predictions from these new untested
models are being presented at international meetings even though results differ from established
paleotsunami measurements by factors as large as four. These substantial differences have attracted
press attention, requiring hazard mitigation professionals to provide public explanations of the
discrepancies. Since an increased number of nations in tsunami-prone regions around the world must
develop tsunami mitigation plans, both validation and verification are essential for all numerical models
used in planning. Validation refers to the process of ensuring that the model solves the parent equations
of motion accurately, and is accomplished through comparison with analytical solutions. Verification
refers to the process of ensuring that the model represents geophysical reality, and is accomplished
through comparison with both laboratory measurements and field measurements. The gold standard for
inundation numerical codes must include validation, verification, and the essential step of formal
documentation in the peer-reviewed scientific literature. This process must be considered continuous; it
is essential that even proven models be routinely reviewed and subjected to additional testing and
documentation as new knowledge and data are acquired. So far, only a few existing numerical models
have met these standards, and such models must be the only choice for inundation forecast modeling;
the consequences of failure are too serious to risk a lower standard. A forecast system also requires
accurate tsunami measurements and well-tested numerical procedures for inverting the measurements
to produce predictions with a proven model. Clearly, however, there is no absolute certainty that even a
properly validated and verified numerical code will produce accurate, real-time inundation forecasts; this
is why multiple models should be implemented to improve forecast system robustness. We discuss
analytical, laboratory, and field benchmark tests by which tsunami models can be validated, verified and
formally documented in peer-reviewed journals indexed by ISI. This painstaking process may appear
onerous, but is the only defensible methodology when human lives are at stake. Model standards and
procedures that reflect this approach are being adopted for implementation in the U.S. Tsunami
Forecasting System that is under development by the National Oceanic and Atmospheric Administration.
Keywords: tsunami modeling, standards benchmarks, tested model