1.0 TITLE: The Causes Of Earthquake
1.1 The reason for choosing this title is:-
Ø To know the causes of earthquake that might occur in the outsider country
Ø To understand the effect of the earthquake toward the environment
Ø To know further about their causes.
1.2 my general purpose
Ø to inform
1.3 My specific purpose
Ø To inform the audience about the causes of earthquake.
1.4 My general purpose/ main points
Ø The definition of earthquake
Ø The types of earthquake
Ø The causes of earthquake
Ø The effects of earthquake
2.1 Definition of Earthquake
i. From Wikipedia (2008): the result of a sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes are measured with a seismometer; a device which also records is known as a seismograph. The moment magnitude (or the related and mostly obsolete Richter magnitude) of an earthquake is conventionally reported, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale[1]
ii. From Dictionary Oxford Fajar(2009): sudden violent shaking of the ground, caused by movements within the earth’s crust[2]
iii. From Dictionary of English Language (2009): A sudden movement of the earth's crust caused by the release of stress accumulated along geologic faults or by volcanic activity. Also called seism, temblor[3]
iv. From Free Dictionary(2009): a sudden release of energy in the earth's crust or upper mantle, usually caused by movement along a fault plane or by volcanic activity and resulting in the generation of seismic waves which can be destructive[4]
There are four types of earthquake which are:-
1. Tectonic earthquake
· The earth’s crust consists of loose broken fragments of lands known as the tectonic plates. These tectonic plates have the ability to slowly and gradually move. These plates can away from each other, towards each other, can collide or can slide past each other[5]. All tectonic plates have internal stress fields caused by their interactions with neighboring plates and sedimentary loading or unloading (e.g. deglaciation). These stresses may be sufficient to cause failure along existing fault planes, giving rise to intraplate earthquakes. Besides that, majority of tectonic earthquakes originate at the ring of fire in depths not exceeding tens of kilometers. Earthquakes occurring at a depth of less than 70 km are classified as 'shallow-focus' earthquakes, while those with a focal-depth between 70 and 300 km are commonly termed 'mid-focus' or 'intermediate-depth' earthquakes[6].
· Volcanic earthquake are comparatively less common than the tectonic earthquakes and usually occur either before or after a volcanic. There are two types of volcanic earthquakes:-
(a) Volcanic tectonic earthquake
Ø These earthquakes occur usually after a volcanic activity has taken place. The magma that erupts during an earthquake leaves a space, to fill the space left by the magma the rocks move towards the space to fill it in, causing severe earthquakes.
(b) Long period volcanic earthquakes
Ø These earthquake normally occur post a volcanic eruption. Few days before the great explosion, the change in heat of magma below the earth’s surface creates seismic waves, causing an earthquake.
3. Collapse earthquake
· Collapse earth quakes are comparatively small earthquakes and they take place around underground mines. These earthquakes are also referred to as the mine bursts. The collapse earthquakes are caused by the pressure induced within the rocks. It results in the collapse of the roof of the mine which causes further tremors. Collapse earthquakes are common in small towns near these underground mines[7].
4. Explosion earthquake
· The explosions earthquakes are caused due to the nuclear explosions. These man induced earthquakes are one of the biggest side effects of the modern nuclear war[8]
· Besides that, it results from the explosion of nuclear and chemical devices. We can measure motion from large tectonic earthquakes using GPS because rocks on either side of a fault are offset during this type of earthquake[9]
· In the 1930s during the American nuclear tests many small villages and towns suffered through such tremors, many of them were completely destroyed due to this heinous act.
a) Fault Movement
· When tectonic plates move, the motion is slow and steady. When fault move to allow changes in the shape of crust, their motions can be slow and steady (this is known as fault creep). Sometimes, there is interference with this gradual motion and fault sticks. While it is stuck, the plates below continue to move, and a great deal of the pressure and energy build up. At same point, this energy must be released. When something causes the friction between two stuck fault block to let go, there are a sudden, massive release of energy that causes movement along the fault plane. This energy travels through the ground, away from the fault, in waves creating an earthquake[10]
b). Eruption of Volcanoes
· Eruption of volcanoes is sudden and is known volcanoes are seat of inner disturbance and can affect the plates. Volcanoes are erupt because of the molten of magma under the crust of the earth is under enormous pressure and to release that pressure it looks for an opening and exerts pressure on the earth’s crust and the plate in turn. A place, which is the seat of an active volcano, is often prone to earthquakes as well because the pressure that is exerted by the magma exceeds the limit these plates move and that causes earthquakes.
· Earthquakes are also caused after a volcanic eruption since the eruption also leads to a disturbance in the position of plates, which either move further or resettle and can result into severe or light tremors
c). Movement of Plates
· Movement of plates can be caused due to various reasons like under crust waves or cracks in the plates.
· The outer layer of the earth is divided into many sections known as plates, which are floating on the molten magma beneath the earth’s crust. Now the movement of these plates is determined by the convection current in the molten magma. The heat makes these plates rise and vice versa. Therefore after intervals there are plates that get submerged in the molten magma and their plates that rise upwards and at times even new crust is formed from the molten magma which in turn forms a new plate until it connects itself with the already existing ones.
· This movement disrupts the balance and position of all plates, which leads to tremors, which are called earthquakes[11]
- Shaking and ground rupture
Ø Shaking and ground rupture are the main effects created by earthquakes, principally resulting in more or less severe damage to buildings and other rigid structures. The severity of the local effects depends on the complex combination of the earthquake magnitude, the distance from the epicenter, and the local geological and geomorphologic conditions, which may amplify or reduce wave propagation. The ground-shaking is measured by ground acceleration. This effect is called site or local amplification. It is principally due to the transfer of the seismic motion from hard deep soils to soft superficial soils and to effects of seismic energy focalization owing to typical geometrical setting of the deposits.
Ø Ground rupture is a visible breaking and displacement of the Earth's surface along the trace of the fault, which may be of the order of several meters in the case of major earthquakes. Ground rupture is a major risk for large engineering structures such as dams, bridges and nuclear power stations and requires careful mapping of existing faults to identify any likely to break the ground surface within the life of the structure[12]
Ø Earthquakes, along with severe storms, volcanic activity, and coastal wave attack, and wildfires, can produce slope instability leading to landslides, a major geological hazard. Landslide danger may persist while emergency personnel are attempting rescue[13]
iii. Fires
Ø Earthquakes can cause fires by damaging electrical power or gas lines. In the event of water mains rupturing and a loss of pressure, it may also become difficult to stop the spread of a fire once it has started.
Ø Besides that, it can caused flammable materials that being throw into a cooking or heating.
Ø For example, more deaths in the 1906 San Francisco earthquake were caused by fire than by the earthquake itself.
Ø A flood is an overflow of any amount of water that reaches land. Floods occur usually when the volume of water within a body of water, such as a river or lake, exceeds the total capacity of the formation, and as a result some of the water flows or sits outside of the normal perimeter of the body.
Ø However, floods may be secondary effects of earthquakes, if dams are damaged.
Ø It occur when the underwater earthquake produce tidal wave that will lead to the tsunami.
v. Human impacts
Ø Earthquakes may lead to disease, lack of basic necessities, loss of life, higher insurance premiums, general property damage, road and bridge damage, and collapse or destabilization (potentially leading to future collapse) of buildings.
Ø Earthquakes can also precede volcanic eruptions, which cause further problems. For example, substantial crop damage, as in the "Year without a summer" (1816).
In my conclusion, I hope all the audience will know the causes of earthquake that will give a big impact if it happens in our country. Besides that, I also hope that all the teenagers have their own responsibilities in order to give their help toward earthquake victims. It is because normally earthquake victim are contribute all of people and the helper which come are not enough to help all the victims. So, as a teenager they can fill the leisure times with these activities. Lastly, I also hope all the people will make sure that they are being prepared themselves if there are a sign of earthquake to make sure that they are not loss their loved ones, property and others thing that important to them.
Bruce A. Bolt (2005). Earthquake. 5th Edition. W.H Freeman. 320 pages
David S. Brumbaugh. (1999). Earthquake: Science and Society. The University Of California. Prentice Hall. 251 Pages
http://www.thefreedictionary.com/earthquake
Houghton Mifflin. (2009). Dictionary of The English Language. 4th Edition. The American heritage. Houghton Mifflin Company.
http://en.wikipedia.org/wiki/Earthquake
http://hubpages.com/hub/Types-Of-Earthquakes
http://scign.jpl.nasa.gov/learn/eq2.htm
http://www.buzzle.com/articles/what-causes-earthquake.htm
Kauffman, Judson, Physical Geology, 8th Edition, New Jersey : Prentice Hall, 1990
Minoru Wakabayashi. (1986). Design of Earthquake: Resistant Building. 309 pages
Sara Hawker, Little Oxford English Dictionary, 9th Edition, Page 215
Timothy M. Kusky (2005). Encyclopedia of Earth Science. InfoBase Publishing. 510 Pages
[1] http://en.wikipedia.org/wiki/Earthquake
[2] Sara Hawker, Little Oxford English Dictionary, 9th Edition, Page 215
[3] Houghton Mifflin. (2009). Dictionary of The English Language. 4th Edition. The American heritage. Houghton Mifflin Company.
[5] http://hubpages.com/hub/Types-Of-Earthquakes
[6] http://en.wikipedia.org/wiki/Earthquake
[7] http://hubpages.com/hub/Types-Of-Earthquakes
[10] Kauffman, Judson, Physical Geology, 8th Edition, New Jersey : Prentice Hall, 1990
[11]Article from Poushali Ganguly http://www.buzzle.com/articles/what-causes-earthquake.html
[12] http://en.wikipedia.org/wiki/Earthquake
