BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:Weakly nonlinear shoaling of tsunami: the phenomenon of self-induc ed transparency - Victor Shrira (Keele University) DTSTART:20220714T133000Z DTEND:20220714T140000Z UID:TALK175886@talks.cam.ac.uk DESCRIPTION:The evolution of tsunamis is reasonably well described by weak ly nonlinear models which treat them as long low-frequency surface waves i nteracting with the topography. While in the deep ocean tsunamis are in ge neral small-amplitude perturbations (of the order of 10 cm or less)\, thei r height may increase considerably through shoaling and refractive focusin g. \;One of the key factors determining the outcome of a tsunami for p articular shore is the share of the energy which passes through and reflec ted\, called the transmission and reflection coefficients. Often the obser ved tsunami reflections might be substantial\, up 90% of the incoming ener gy. Hence\, it is important to understand and properly describe tsunami re dlection and transmission. In one of the most common scenarios  \; tsu namis disintegrate into `solibores&rsquo\; (trains of cnoidal waves/solito ns)\, or\, in other words\, form a dispersive shock. This process has impo rtant implications for the threat of tsunami to coastal communities. The s hoaling solibores grow faster than linear waves\, as a result they become significantly steeper and attain higher-amplitudes than the tsunami source . They focus high velocity and accelerations in small packets that create a more effective forcing for nearshore currents and sediment transport. On e of the main key open questions concerned with tsunami shoaling is how no nlinearity affects the incident wave reflection and transmission. Here\, b y investigating numerically within the framework of the Boussinesq equatio ns the disintegration of a shoaling pulse into solibore\, we show that the emergence of a well developed solibore considerably reduces the incident wave reflection by the bottom slope\, or\, alternatively\, increases the t otal mass and momentum transmission passing through the slope and onto the shoreline. The effect is explained by the disintegration of an initially long pulse of a characteristic scale with a substantial reflection from th e slope into a solibore made of robust nonlinear waves of much shorter sca les. These shorter scales experience very little reflection. Thus\, a fini te amplitude largely pulse passes through\, while a small amplitude one is reflected. In nonlinear optics and plasmas a superficially similar phenom enon when a small amplitude wave cannot get through\, while the finite amp litude one can\, is called `self-induced transparency&rsquo\;\, we apply t his term to our context. We conclude by stating that the described effect of self-induced transparency caused by disintegration of tsunami into soli bores considerably increases its damaging potential.\n \;\nCo-Authors and Affiliations: Joseph Jefferson and Alex Sheremet LOCATION:Seminar Room 1\, Newton Institute END:VEVENT END:VCALENDAR