WATER WAVE DYNAMICS AND THE SECRET OF THE TSUNAMIS Presenters: -Isaac Katz -Zsuzsanna Kis -Kinneret Rozales Mentor: Ronen Avni Location: Haifa, Technion city, Faculty Of Civil Engineering.

THE PHYSICS OF WAVES The following mathematical equation, commonly referred to as the wave equation served as the scientific foundation for this work. Its derivatives are also here shown, although for shortness of space not explained. These basic equations have uncovered the firsts steps towards an understanding of fluid dynamics in general and water-wave behavior in particular and I think them crucial for any one to know who has an interest in this subject especially as they don’t require advanced education to understand.

WATER-WAVE EQUATION AND ITS DERIVATIVES

WAVE SPEED EQUATION Long waves are non-dispersive: Their wave speed is independent of their period. It depends only on the water depth, in the form: ( c is wave speed, h water depth, g gravity). where z is the time dependent surface elevation (wave amplitude) and u the horizontal particle velocity. It follows that u is independent of depth and the vertical particle velocity varies linearly with depth. Particles move on very flat elliptic paths in nearly horizontal motion. The velocity structure in a long wave is described by

WAVES IN THE LAB We can see examples of waves all around us, Here we experiment with many objects to find out their properties And see how they relate to waves. Using a pendulum, a moving board and some sand we can see the interesting results that show us how the same underlying sinus wave shape forms on different situations and materials.

And here we can see a wave forming from the rhythmical up and down movement of a spring rope. The faster the rope is moved the more waves are formed, with nodes and anti-nodes developing harmoniously with the movement, we can thus see the rope evolving from a single waveform into multiple, complicated patterns which are not always symmetric. A demonstration of waves with normal conditions approaching a ‘shore’ if looked at closely one can distinguish de similarities of the basic wave form with the picture in the right.

WHAT DOES TSUNAMI MEAN? Japanese word which in English means Harbor Wave Japanese word which in English means Harbor Wave Commonly known as ‘tidal waves’ Commonly known as ‘tidal waves’ Composed of a train of waves Composed of a train of waves

CHARACHTERISTICS OF TSUNAMIS Long wave periods Long wave periods Can achieve extreme heights Can achieve extreme heights Are rare events Are rare events At open sea, they travel extremely fast, reaching velocities of 700 Km/H (400 Mh/H) At open sea, they travel extremely fast, reaching velocities of 700 Km/H (400 Mh/H)

WHAT CAUSES TSUNAMIS Sub-marine earthquake Landslides Volcanic eruptions Cosmic – body impacts (asteroids, comets, etc.)

WHAT HAPPENS TO A TSUNAMI AS IT APPROACHES LAND Its height grows due to shoaling They lose some energy as they rush onshore Depending on the particular beach this makes surfing possible

SPECULATION ON A MASSIVE TSUNAMI If an asteroid or comet 4 kilometers in diameter were to strike the earth the resulting wave can make entire coastlines disappear and wreck havoc on national infrastructures. If the body were large enough, it would achieve the status of ELE (Extinction Level Event) and change our fundamental way of life If an asteroid or comet 4 kilometers in diameter were to strike the earth the resulting wave can make entire coastlines disappear and wreck havoc on national infrastructures. If the body were large enough, it would achieve the status of ELE (Extinction Level Event) and change our fundamental way of life

THE IMPACT ON HUMANS Tsunamis are considered catastrophic events Tsunamis are considered catastrophic events They are rare, but very difficult to predict They are rare, but very difficult to predict The death tolls of an attack can reach tens of thousands The death tolls of an attack can reach tens of thousands

WAVE RESONANCE An interesting wave phenomenon is the resonance effect that occurs when a tsunami, or any other type of wave, comes into indirect contact with another medium which has the same properties and part of its energy is transferred to the other medium, thereby ‘resonating’ itself into places which otherwise it would have been impossible to enter.

WAVE SUPERPOSITIONS The following mathematical equations expresses the processes of wave superpositions; when two waves come together and form a single one with characteristics of both. In the picture we see an electronic wave simulator which is showing this kind of phenomenon.

THANKS: Ronen Avni for teaching us so very patiently the material and for his great examples. Ronen Avni for teaching us so very patiently the material and for his great examples. Technion for letting us use their facilities Technion for letting us use their facilities Faculty of civil engineering Faculty of civil engineering Ami and Guy for driving us around and help Ami and Guy for driving us around and help