"January 04, 2005
FACTS
Physics of Tsumani
Earthquake passes, Tsunami comes… Physics of Tsunami from Earthquake Original is published in Cakrawala, the supplement of Pikiran Rakyat Newspaper, Thursday 30 Dec 2004 [Bahasa Indonesia] This article had been modified according to recent data. The modification doesn't change the substance Earthquake is a common phenomenon for us. It may be caused by several factors, such as (1) volcanic eruption, (2) meteor impacts, (3) underground explosions (like nuclear test), and (4) movement of plate of Earth. We often experience the earthquake from no. 4, or so-called tectonic earthquake. Seismology developed theory of plate tectonics, in order to explain how the tectonic earthquake happens. The basic idea is that the lithosphere the outer layer of Earth) – is comprised of many plates that slide over the lubricating athenosphere layer. At the boundaries between these huge plates of soil and rock, three different things can happen: (1) plates can move apart, and then magma flows up from the layers of mantle below the lithosphere. (2) Plates can push together, and then one of plate subduct the other, or if neither plate is subduct under the other could form mountain. (3) Plates slide against each other, one to north and the other to south for example.
All three predictions will yield a vibration then go through the soil and rock. This vibration is called seismic wave or the tectonic earthquake when it reaches the surface. The place where the wave initiates in the first time is called focus. If the second prediction happens in the bottom of sea, when one of plate subduct the other, the water above the deformed area is displaced from its equilibrium position. Waves are formed as the displaced water mass, which acts under the influence of gravity,
1
attempts to regain its equilibrium. When large areas of the sea floor elevate or subside, a tsunami can be created. Tsunami is a Japanese word with the English translation, "harbor wave." Represented by two characters, the top character, "tsu," means harbor, while the bottom character, "nami," means "wave." Physics of Tsunami Tsunami can be explained by phenomenon of wave traverse; its energy is function of height (amplitude) and speed. Height depends on the wavelength. A tsunami has wavelength in order of hundreds kilometers (compare with normal wave in meters!), behave as shallow-water wave. A wave becomes a shallow-water wave if ratio of depth of water and wavelength is lesser then 0.05. The speed of shallow-water wave is square root of (g*d), g is gravity acceleration and d is depth of water. Imagine, at the depth 10 km in India Ocean, a tsunami will have initial speed around 300 m/sec or around 1000 km/hours. The speed decrease as depth increase when move toward beach. However, its energy tends constant. This follows the energy loss rate of transversal wave is inverse with its wavelength; i.e. the bigger wavelength the smaller energy loss. Then energy of tsunami tends constant. Because of the energy constant, decreasing of speed will increase the height. Scientists observe with speed of 1000 km/hours toward beach, tsunami can have height 30 meter. Earthquake and Tsunami in Aceh
2
The tectonic earthquake occurred on 26 Dec 04 at 7.58 WIB, at magnitude 9.0 scale of Richter (USGS). It places this international disaster the forth most awful disaster since 1900. the first in Chili (1960, 9/5 SR), Alaska (1964, 9.2 SR), and again Alaska (1957, 9.1). The focus was predicted at coordinate 3.316°N, 95.855°E, some 160 m west of Sumatera, at a depth of 30 km below mean seal level. This is at the extreme western end of the "Ring of Fire", an earthquake belt that accounts for 81% of the world's largest earthquakes. The quake itself (apart from the tsunamis) was felt as far away as Bangladesh, India, Malaysia, Myanmar, Singapore, Thailand and the Maldives. The earthquake was unusually large in geographical extent. An estimated 1200 km of plate slipped 20 meters along the subduction zone where the India Palte dives under the Burma palte. The seabed of the Burma plate is estimated to have risen several metres vertically up over the India plate, creating shock waves in the Indian Ocean that traveled at up to 800 km/h (500 mi/h), forming tsunamis which, while less than a meter high in deep water, resulted in huge waves they reached land. The Power and the Impact to Earth-physical The total energy released by a magnitude 9.0 earthquake is equivalent to 32,000 megatons of TNT or 133 exajoules (1.33×1020 joules). This exceeds the total amount of energy consumed in the United States in one year by 30%, or the energy released by the wind of a hurricane like Hurricane Isabel over a period of 70 days. Using the mass-energy equivalence formula E = mc^2, this amount of energy is equivalent to a mass of about 1500 kg. Equivalently, this amount of energy is enough to boil 10,000 liters (2,600 US gallons) of water for every person on Earth.
3
That such huge energy has forced lands to move. Some small islands in soutwest Sumatera has moved 20 meter to southwest. Sumatera tip has moved 36 m to southwest. Some small island even gone forece. New lakes and rivers created in ex-land of Aceh, disconnect transportation to exvillages that also gone in the world's map. Let’s pray to God, give your hands to help the victims! By Febdian Rusydi Alumni of Engineering Physics ITB, student of theoretical physics, KVI, RuG, the Netherlands (from many sources)
Posted by Buyung at January 4, 2005 02:56 AM
http://acehupdate.degromiest.nl/archives/000989.php
4
..."
|
You need to upgrade your Flash Player , or try to enable javascript in order see this document properly.
|
|
Comments
