A tidal wave or tsunami (Japanese word that means wave in port or hidden wave) consists of a series of waves that are generated by disturbances in the oceanic floor, or by an earthquake, volcanic eruptions, slidings or impacts of meteorites. In deep waters they can move at 500 miles per hour, although they reaches only inches in heights. The distance between the waves can be of up to 466 miles. When they arrive at the coast it reduces his speed and the distance between the waves and increases the height , reaching tens of feet in height. Tsunamis evolves in three phases:
1, Generation. A Process in which a disturbance in the marine bottom, for example, movement throughout a fault, turns the surface of the sea in a tsunami. The height that mainly reaches the waves depends of the magnitude, speed may vary depending of the duration of the displacement and the depth of the sea.
2, Propagation. In this stage the energy is transported from the zone of generation to the coast. The height of the wave is little with respect to its length. Variations of the depth of the bottom of the sea can modify the direction of the wave. As approaches the coast and the sea becomes less deep, the energy is conteined in a little volume of water causing high wavers and fast currents.
3, Flood. The tidal waves can be presented as stirred up waves or a flood. The waves can reach tens of height in feets, although five feet are sufficient to cause disasters. If there are no cliffs or topograpy is very escarped, waters can penetrate hundreds of feet inside. In many occasions before the flood happens, a backward movement of the sea occurs.
History of tidal waves in Puerto Rico
Tidal wave of 1867
November 18 of 1867, 20 days after hurricane San Narciso whipped the zone, an earthquake of magnitude 7,3 that was felt with greater intensity in the Virgenes Islands and the east area the Island. The epicenter of the earthquake was located in the Passage of Anegada between the islands of St. Thomas, Santa Cruz and Vieques. The tidal wave that took place reached near 20 feet in St. Thomas and Santa Cruz. In Yabucoa the sea receed from the shore and came back 450 feet over land.
