The model was presented as part of a seminar of the Environmental, Water and Agricultural Engineering Unit at the Technion. The model was developed by Professor Michael Stiassnie from the Faculty of Civil and Environmental Engineering at the Technion.
A model developed by Professor Michael Stiassnie from the Faculty of Civil and Environmental Engineering at the Technion and which enables tsunami prediction at short notice was presented this week as part of a seminar of the Environmental, Water and Agricultural Engineering Unit at the Technion.
Tsunami events, which sometimes claim the lives of hundreds of thousands of people in one day, are the result of earthquakes in the middle of the sea. The uplift of the land under the water creates a very low (tens of centimeters high) and very long (40 kilometers) wave. This wave initially moves at a speed of about 200 meters per second, and gradually slows down. Despite this deceleration, the wave rises, when it approaches the shore, to a height of a few meters or even tens of meters, and therefore in many cases causes enormous damage to property and human life.
The development of 'tsunami warning', which may save many, is currently occupying many countries, bodies and researchers. However, to date no reliable and accurate enough warning mechanism has been found. The problem in locating the tsunami waves in their formation phase stems from the fact that, as mentioned, these are very low waves.
In a study conducted at the Technion, a model was developed based on the detection of acoustic-gravitational waves that are created at the same time as the tsunami wave as a result of the underwater earthquake. While the tsunami wave moves at an initial speed of 200 meters per second, the acoustic wave moves at a speed 7.5 times higher: 1,500 meters per second. In the event that the earthquake occurs at a great distance from the coast - 1,000 kilometers or more - these two waves reach the coast with a considerable difference (an hour or even more). Therefore, the acoustic wave may be a warning of the approach of a tsunami wave, thus enabling an early evacuation of the population.
The next challenge, Professor Stiasani explained in his lecture, was the detection of those acoustic waves. Since these are very low waves (about 10 centimeters) it is difficult to locate them from the wind waves. However, the uniqueness of these waves is that, unlike wind waves, their speed and strength near the bottom are maintained during movement, so they can be measured using underwater sensors. In this way, these waves enable an effective warning, at least in cases where the earthquake occurred far from the coast. Professor Shtiasani, who conducted the research with three of his students - Dr. Osama Kadri, PhD student Gali Hendin and Master's student Erez Ayyub - explained that the theoretical model takes into account the compressibility of sea water. "Since the compressibility of liquids is quite marginal, it is customary to study waves and currents in the sea with the assumption that the water is incompressible. Here, as mentioned, the compressibility of the water was taken into account, and this assumption led to the new findings." Professor Stiasni points out that the aforementioned model has another value besides tsunami prediction: the reproduction of the various parameters (duration, location, magnitude of displacement, etc.) of the earthquake that generated the waves.
Professor Stiasni's lecture opened the symposium of the Environmental, Water and Agricultural Engineering Unit at the Technion, and was held in memory of Professor Peter Indelman. Professor Indelman, who was a faculty member in the unit, was born in Russia, and in 1980 he completed his doctorate at the University of Kazan, on the topic "Instability of two-phase flow in a heterogeneous medium". Since then, he has been dealing with flow in a porous medium (soil, mainly), and has become one of the 'nephiles of our unit', as defined by Professor Stiasni. "Unfortunately, Peter passed away in 2005, but his publications still resonate in the professional community. His articles garnered more than 700 citations, and in 2011 alone he was cited fifty times - that is, his works are relevant and contemporary even today."
The seminar included a series of lectures by the members of the unit: Professor Yohai Carmel ("Competitive suppression in nature: theory or myth"), Professor Yaakov Meman ("Forty years of research on air pollution"), Professor Dan Lieberson ("Wind waves: formation, development and directional dispersion", Professor Shmuel Hasid ("Layered layer flow with axial symmetry"), and Professor Guy Ramon ("Smart" membranes to prevent fouling in desalination processes").
