Submarine Earthquake

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Submarine Earthquake :

Submarine Earthquake Presented By K.Lavanya M.Tech

INTRODUCTION::

INTRODUCTION: A submarine , undersea , or underwater earthquake It is an earthquake that occurs underwater at the bottom of a body of water , especially an ocean . They are the leading cause of tsunamis . The magnitude can be measured scientifically by the use of either the Richter scale or the Mercalli scale .

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Understanding plate tectonics helps to explain the cause of submarine earthquakes. The Earth's surface or lithosphere comprises tectonic plates which average approximately 50 miles in thickness, and are continuously moving very slowly upon a bed of magma in the asthenosphere and inner mantle . Tectonic plate boundaries

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The plates converge upon one another, and one subducts below the other, or, where there is only shear stress, move horizontally past each other ( see transform plate boundary below). Little movements called fault creep are minor and not measurable. The plates meet with each other, and if rough spots cause the movement to stop at the edges, the motion of the plates continue. Convergent plate boundary trench formation and dynamics

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When the rough spots can no longer hold, the sudden release of the built-up motion releases, and the sudden movement under the sea floor causes a submarine earthquake. This area of slippage both horizontally and vertically is called the epicenter , and has the highest magnitude, and causes the greatest damage

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As with a continental earthquake the severity of the damage is not often caused by the earthquake at the rift zone, but rather by events which are triggered by the earthquake. Where a continental earthquake will cause damage and loss of life on land from fires, damaged structures, and flying objects; a submarine earthquake alters the sea bed floor, resulting in a series of waves, and depending on the length and magnitude of the earthquake, huge tidal waves and tsunamis , which bear down on coastal cities causing property damages and loss of life.

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Submarine earthquakes can also damage submarine communications cables , leading to widespread disruption of the Internet and international telephone network in those areas. This is particularly common in Asia, where many submarine links cross submarine earthquake zones such as the Pacific Ring of Fire .

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Tsunamis are a series of catastrophic ocean waves that are formed after submarine earthquakes, volcanic eruptions, landslides, or asteroids striking the earth. Asteroids may not be a normal occurrence; however, earthquakes, volcanic eruptions, and landslides under the ocean happen more frequently than you realize.

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produced by a submarine earthquake, volcanic eruption, sediment slide Seafloor movements in  submarine earthquake

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Tsunamis generated by submarine earthquakes travel at subsonic speed across.

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Once the earthquake occurs and the ocean floor is disturbed, waves travel outward in all directions from the focus of the earthquake. Imagine throwing a rock into a lake on a summer day. When the rock breaks the surface of the water, ripples appear and radiate outward from the point where the rock entered the water.

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The waves then travel through the open sea. In the open ocean, these waves may reach a speed up to 500 miles per hour (720 kilometers per hour). Their wavelengths may also be up to several hundred miles. One surprising fact is that their heights at this point may only reach less than three feet (one meter). Even a ship at sea would not notice this tsunami wave.

Tectonic plate boundaries::

Tectonic plate boundaries: The different ways in which tectonic plates rub against each other under the ocean or sea floor to create submarine earthquakes. The type of friction created may be due to the characteristic of the geologic fault or the plate boundary as follows. Some of the main areas of large tsunami producing submarine earthquakes are the Pacific Ring of Fire and the Great Sumatran fault

Convergent plate boundary:

Convergent plate boundary The older, and denser plate moves below the lighter plate. The further down it moves, the hotter it becomes, until finally melting altogether at the asthenosphere and inner mantle and the crust is actually destroyed. The location where the two oceanic plates actually meet become deeper and deeper creating trenches with each successive action. There is an interplay of various densities of lithosphere rock, asthenosphere magma, cooling ocean water and plate movement for example the Pacific Ring of Fire . Therefore the site of the sub oceanic trench will be a site of submarine earthquakes; for example the Mariana Trench .

Transformers (megatron, optimus prime)transform plate movement :

Transformers ( megatron , optimus prime)transform plate movement A transform-fault boundary, or simply a transform boundary is where two plates will slide past each other, and the irregular pattern of their edges may catch on each other. The lithosphere is neither added to from the asthenosphere nor is it destroyed as in convergent plate action.

List Of Major Submarine Earthquakes :

List Of Major Submarine Earthquakes May 4, 1998 A part of the island of Yonaguni was destroyed by a submarine earthquake . May 22, 1960 , Valdivia earthquake (Great Chilean Earthquake) The epicenter is off the coast of South Central Chile . Magnitude of 9.5.This is the strongest earthquake ever recorded. December 20, 1946 , Nankaido earthquake The epicenter is off the southern coast of Kii Peninsula and Shikoku , Japan . Magnitude of 8.1 December 7, 1944 Tōnankai earthquake .The epicenter is about 20 km off the coast of the Shima Peninsula in Japan. Magnitude of 8.0

References::

References: www.wikipedia.org www.infoplease.com edhelper.com

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