deligero_educ6.b ppt-earthquake

EARTHQUAKES:

EARTHQUAKES EZENPHERL DELIGERO BSED BIO III MR.REGIEL ARNIBAL EDUC 6 B MTh 7:30-9:00

EARTHQUAKES:

EARTHQUAKES

WHAT IS AN EARTHQUAKES?:

WHAT IS AN EARTHQUAKES? An earthquake(also known as a quake, tremor, temblor or seismic activity) is the result of a sudden release of energy in the Earth's crust that creates seismic waves . It is a the shaking of the ground caused by the sudden breaking and movement of large sections ( tectonic plates ) of the earth's rocky outermost crust. The edges of the tectonic plates are marked by faults (or fractures). Most earthquakes occur along the fault lines when the plates slide past each other or collide against each other An earthquake is a tremor of the earth's surface usually triggered by the release of underground stress along fault lines. This release causes movement in masses of rock and resulting shock waves.

What are the causes of earthquakes?:

What are the causes of earthquakes? Two main causes of earthquakes: First, they can be linked to explosive volcanic eruptions; they are in fact very common in areas of volcanic activity where they either proceed or accompany eruptions . Secondly , they can be triggered by Tectonic activity associated with plate margins and faults. The majority of earthquakes world wide are of this type.

Types of earthquakes:

Types of earthquakes The type of earthquake depends on the region where it occurs and the geological make-up of that region. The most common are the following: Tectonic earthquakes these occur when rocks in the earth's crust break due to geological forces created by movement of tectonic plates . volcanic earthquakes, occur in conjunction with volcanic activity . Collapse earthquakes are small earthquakes in underground caverns and mines . The immediate cause of ground shaking is the collapse of the roof of the mine or cavern . explosion earthquakes result 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.

MEASURING EARTHQUAKES:

MEASURING EARTHQUAKES Seismologists use two main devices to measure an earthquake: SEISMOSCOPE- The seismoscope is an instrument that measures the occurrence or the time of an occurrence of an earthquake . SEISMOGRAPH- The seismograph is an instrument that measures seismic waves caused by an earthquake

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Heng’s Seismoscope called the Dragon jar , it is the first seismoscope that measures earthquakes precisely and accurately The seismoscope is an instrument that measures the occurrence or the time of an occurrence of an earthquake (“Inventors”).  Unlike other measuring devices, the seismoscope is a simple device without any technological background . The seismoscope is the oldest and most accurate instrument for measuring earthquakes direction.

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SEISMOGRAPH The seismograph is an instrument that measures seismic waves causedby an earthquake. The seismograph has three main devices: the Richter Magnitude Scale the Modified Mercalli Intensity Scale Moment-Magnitude Scale.

The Richter Magnitude Scale:

The Richter Magnitude Scale Charles Francis Richter (April 26, 1900 - September 30, 1985), was a seismologist and physicist from Ohio. Richter is most famous as the creator of the Richter magnitude scale which, until the development of the moment magnitude scale in 1979, quantified the size of earthquakes.

The Richter Scale:

The Richter Scale Richter scale, which measures the magnitude of earthquakes, was developed in 1935 by Charles F. Richter at the California Institute of Technology. The magnitude is determined by readings of the seismic waves resulting from the earthquake's vibrations. The Richter scale doesn't measure quake damage; this is dependent on a variety of factors including population at the epicenter, terrain, depth, etc. It is also known as earthquake magnitude scale.

Richter Magnitudes:

Richter Magnitudes Richter Magnitudes Description Earthquake Effects Frequency of Occurrence Less than 2.0 Micro Micro-earthquakes, not felt. About 8,000 per day 2.0-2.9 Minor Generally not felt, but recorded. About 1,000 per day 3.0-3.9 Minor Often felt, but rarely causes damage. 49,000 per year (est.) 4.0-4.9 Light Noticeable shaking of indoor items, rattling noises. Significant damage unlikely. 6,200 per year (est.) 5.0-5.9 Moderate Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings. 800 per year

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6.0-6.9 Strong Can be destructive in areas up to about 160 kilometres (100 mi) across in populated areas. 120 per year 7.0-7.9 Major Can cause serious damage over larger areas. 18 per year 8.0-8.9 Great Can cause serious damage in areas several hundred miles across. 1 per year 9.0-9.9 Great Devastating in areas several thousand miles across. 1 per 20 years 10.0+ Epic Never recorded; see below for equivalent seismic energy yield. Extremely rare (Unknown)

Modified Mercalli Intensity Scale:

Modified Mercalli Intensity Scale Born in Milan , Mercalli was ordained a Roman Catholic priest and soon became a professor of the Natural Sciences at the seminary of Milan. He was removed from the professorship when he was suspected of liberalism for openly supporting a national monument to honor the great philosopher-priest Antonio Rosmini-Serbati . He is best remembered today for his Mercalli scale for measuring earthquakes which is still used today. The Mercalli scale, unlike the more famous Richter scale , doesn't measure the actual energy released by an earthquake but how much effect an earthquake had on a given area, making it poorly suited for measuring earthquakes in sparsely populated areas, but ideal for comparing damage done by various tremors.

Mercalli Intensity:

Mercalli Intensity The effect of an earthquake on the Earth's surface is called the intensity. The intensity scale consists of a series of certain key responses such as people awakening, movement of furniture, damage to chimneys, and finally - total destruction. Although numerous intensity scales have been developed over the last several hundred years to evaluate the effects of earthquakes, the one currently used in the United States is the Modified Mercalli (MM) Intensity Scale. It was developed in 1931 by the American seismologists Harry Wood and Frank Neumann. This scale, composed of 12 increasing levels of intensity that range from imperceptible shaking to catastrophic destruction, is designated by Roman numerals. It does not have a mathematical basis; instead it is an arbitrary ranking based on observed effects.

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Mercalli intensity Observed structural damage I. Instrumental Not felt by many people unless in favourable conditions. II. Weak Felt only by a few people at best, especially on the upper floors of buildings. Delicately suspended objects may swing. III. Slight Felt quite noticeably by people indoors, especially on the upper floors of buildings. Many do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibration similar to the passing of a truck. Duration estimated. IV. Moderate Felt indoors by many people, outdoors by few people during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rock noticeably. Dishes and windows rattle alarmingly.

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V. Rather Strong Felt outside by most, may not be felt by some outside in non- favourable conditions. Dishes and windows may break and large bells will ring. Vibrations like large train passing close to house. VI. Strong Felt by all; many frightened and run outdoors, walk unsteadily. Windows, dishes, glassware broken; books fall off shelves; some heavy furniture moved or overturned; a few instances of fallen plaster. Damage slight. VII. Very Strong Difficult to stand; furniture broken; damage negligible in building of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Noticed by people driving motor cars. VIII. Destructive Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse. Damage great in poorly built structures.

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X. Intense Some well built wooden structures destroyed; most masonry and frame structures destroyed with foundation. Rails bent. XI. Extreme Few, if any masonry structures remain standing. Bridges destroyed. Rails bent greatly. XII. Cataclysmic Total damage - Everything is destroyed. Total destruction. Lines of sight and level distorted

Effects of Earthquakes:

Effects of Earthquakes Earthquakes produce various damaging effects to the areas they act upon. This includes damage to buildings and in worst cases the loss of human life. The effects of the rumbling produced by earthquakes usually lead to the destruction of structures such as buildings, bridges, and dams. They can also trigger landslides. An example of how an earthquake can lead to even more destruction is the 1959 earthquake near Hebgen , Montana. It caused a land slide that killed several people and blocked the Madison River. Due to the fact that the Madison River was blocked, a lake was created which later flooded the nearby town of Ennis.

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Earthquakes have many ways to leave their mark on the land, and most of them are bad. Death. Building damages. Road and bridges destroyed are marks of earthquakes.

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One of the most dangerous effects of an earthquake is a Tsunami. Tsunamis are giant waves that can cause floods and are up to 100 feet tall. They often strike a long way away from the quake, and are very deadly.

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Another side effect of quakes is fire. The shaking causes broken gas lines. Then all it takes is a spark to start a giant fire. Fire was a big problem in the 1906 San Francisco quake.

What To Do during an Earthquake? :

What To Do during an Earthquake? Stay as safe as possible during an earthquake. Be aware that some earthquakes are actually foreshocks and a larger earthquake might occur. Minimize your movements to a few steps to a nearby safe place and if you are indoors, stay there until the shaking has stopped and you are sure exiting is safe.

If indoors: :

If indoors: DROP to the ground; take COVER by getting under a sturdy table or other piece of furniture; and HOLD ON until the shaking stops. If there isn’t a table or desk near you, cover your face and head with your arms and crouch in an inside corner of the building. Stay away from glass, windows, outside doors and walls, and anything that could fall, such as lighting fixtures or furniture. Stay away from glass, windows, outside doors and walls, and anything that could fall, such as lighting fixtures or furniture.

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Use a doorway for shelter only if it is in close proximity to you and if you know it is a strongly supported, load bearing doorway. Stay inside until the shaking stops and it is safe to go outside. Research has shown that most injuries occur when people inside buildings attempt to move to a different location inside the building or try to leave. Be aware that the electricity may go out or the sprinkler systems or fire alarms may turn on. DO NOT use the elevators.

If outdoors :

If outdoors Stay there. Move away from buildings, streetlights, and utility wires. Once in the open, stay there until the shaking stops. The greatest danger exists directly outside buildings, at exits and alongside exterior walls. Many of the 120 fatalities from the 1933 Long Beach earthquake occurred when people ran outside of buildings only to be killed by falling debris from collapsing walls. Ground movement during an earthquake is seldom the direct cause of death or injury. Most earthquake-related casualties result from collapsing walls, flying glass, and falling objects.

If in a moving vehicle :

If in a moving vehicle Stop as quickly as safety permits and stay in the vehicle. Avoid stopping near or under buildings, trees, overpasses, and utility wires. Proceed cautiously once the earthquake has stopped. Avoid roads, bridges, or ramps that might have been damaged by the earthquake.

If trapped under debris :

If trapped under debris Do not light a match. Do not move about or kick up dust. Cover your mouth with a handkerchief or clothing. Tap on a pipe or wall so rescuers can locate you. Use a whistle if one is available. Shout only as a last resort. Shouting can cause you to inhale dangerous amounts of dust.

THINGS TO DO AFTER EARTHQUAKE :

THINGS TO DO AFTER EARTHQUAKE

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A head count should be performed immediately following an earthquake. Whether you are in your office or at home, a head count should be conducted in order to establish whether or not everyone is accounted for and to determine if someone is missing and needs assistance. Check yourself and others for possible injuries. The majority of injuries after an earthquake are relatively mild and usually involve bruises, cuts, and scrapes.

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Check the receiver of your phone to make sure that it is on the hook. Oftentimes during earthquakes, receivers are not off of their hooks, causing the entire phone system to overload and disrupt service if the problem is widespread enough. Grab a flashlight and battery powered radio if the electricity is off. An effort should be made prior to the actual earthquake to designate a flashlight and battery powered radio in the event of emergencies.

REFERENCE:

REFERENCE http://en.wikipedia.org/wiki/earthquake http://en.wikipedia.org/wiki/mercalli_intensity_scale http://geography.about.com/library/misc/blmercalli.htm http://scign.jpl.nasa.gov/learn/eq2.htm http://library.thinkquest.org/16132/html/quakeinfo/effects.html http://ph.images.search.yahoo.com http://earhquake.usg.gov/learn/topics/richter.php http://skywalker.cochise.edu/weller/students/measure-quake/paper.htm http://www.themeter.net/sism e.htm