Applied and Computational Mathematics Seminar

Seminar Details

We present three recent observational and theoretical developments in tsunami science

While it has long been known that tsunamis can be focused and defocused by bathymetric heterogeneities, we consider the case of the sharp refraction expected at a continental shelf, where velocities can vary by as much as a factor of 4 to 5. We confirm that Snell's law is indeed upheld, using both real and simulated time series. This implies that in the presence of a wide continental shelf, distant tsunamis can be considered as impacting the coast at normal incidence.
Motivated by our experience during the 2011 Tohoku tsunami in Tahiti, we explore the conditions under which the leading wave may or may not be that with maximum amplitude. Based on available analytical solutions for simple source models, we find that this "sequencing" of tsunami waves is due to the initiation of dispersion outside the Shallow-Water-Approximation, and as such controlled by a simple combination of distance, effective source size and water depth.
Following the detection of a millimetric tsunami by DART buoys during the 2013 deep Okhotsk earthquake, we explore theoretically the excitation of tsunamis by deep earthquakes. While known events have not produced tsunamis with damaging potential, our lack of knowledge of the maximum size of deep earthquakes leaves open this possibility.