NATURAL DISASTER

NATURAL DISASTER - Earthquake : 

NATURAL DISASTER - Earthquake

What is Earthquake?: 

What is Earthquake? An Earthquake is a sudden, rapid shaking of the earth caused by the breaking and shifting of rocks beneath the earth surface. Over time, stresses build beneath the Earth’s surface. Occasionally, stress is released resulting in the sudden, and sometime disastrous shaking we call an earthquake. The shaking could last seconds or minutes, and there may be several earthquakes over a period ranging from hours to weeks called foreshocks and after shocks, the later decreasing in magnitude with time.

What Causes Earthquake:: 

What Causes Earthquake: The sudden slip at the fault causes the earthquake …….a violent shaking of the Earth when large elastic strain energy released spreads out through seismic waves that travel through the body and along the surface of the Earth.

Moon Hypothesis : 

Moon Hypothesis Some scientists have an idea that moon tides can cause an earthquake in a seismically active area. The moon is known to have tidemaking power 40 % stronger when the moon is at the closest distance from the Earth than it is far from our planet. This power causes the strain and deformation of the Earth's crust. A convincing example of the connection between underground and space events, as American astrophysicists S. Kilston and L. Knopoff think, is frequent earthquakes in California. The scientists proved that the moon gravity power in the full phase causes tension in the earth's crust. All strong (more 6 balls) earthquakes, which occured in California after 1933, were connected with the full and new moon phases, the time of the day (6 am or pm) and the moon positin in the sky.

WHAT IS A FAULT?: 

WHAT IS A FAULT? Earthquakes occur on faults. A fault is a thin zone of crushed rock between two blocks of rock, and can be any length, from centimeters to thousands of kilometers. When an earthquake occurs on one of these faults, the rock on one side of the fault slips with respect to the other. The fault surface can be vertical, horizontal, or at some angle to the surface of the earth. The slip direction can also be at any angle. We classify these into two basic cases: strike slip and dip-slip motion.

The main features of tectonic plates are: : 

The main features of tectonic plates are: The Earth's surface is made up of a series of large plates (like pieces of a giant jigsaw puzzle). These plates are in constant motion travelling at a few centimeters per year. The ocean floors are continually moving, spreading from the centre and sinking at the edges. Convection currents beneath the plates move the plates in different directions. The source of heat driving the convection currents is radioactive decay which is happening deep in the Earth.

Earthquakes and volcanic activity: 

Earthquakes and volcanic activity Earthquakes often occur in volcanic regions and are caused there, both by tectonic faults and the movement of magma in volcanoes . Such earthquakes can serve as an early warning of volcanic eruptions, like during the Mount St. Helens eruption of 1980 . [6] Earthquake swarms can serve as markers for the location of the flowing magma throughout the volcanoes. These swarms can be recorded by seismometers and tiltimeters (a device which measures the ground slope) and used as sensors to predict imminent or upcoming eruptions. [7]

Earthquake storms: 

Earthquake storms Sometimes a series of earthquakes occur in a sort of earthquake storm , where the earthquakes strike a fault in clusters, each triggered by the shaking or stress redistribution of the previous earthquakes. Similar to aftershocks but on adjacent segments of fault, these storms occur over the course of years, and with some of the later earthquakes as damaging as the early ones. Such a pattern was observed in the sequence of about a dozen earthquakes that struck the North Anatolian Fault in Turkey in the 20th century and has been inferred for older anomalous clusters of large earthquakes in the Middle East. [11] [12]

Measuring the shaking: 

Measuring the shaking Magnitude is a measurement of the energy produced by the earthquake and is not what you feel during the event. What you feel is very complex--hard or gentle, long or short, jerky or rolling--and not describable with one number. Aspects of the motion are described by the peak velocity (how fast the ground is moving), peak acceleration (how quickly the speed of the ground is changing), the frequency (energy is released in waves and these waves vibrate at different frequencies just like sound waves), and the duration (how long the strong shaking lasts). Three factors primarily determine what you feel in an earthquake. These are:• 1) magnitude; 2) distance from the fault; and 3) local soil conditions.

PowerPoint Presentation: 

MAGNITUDE When scientists refer to a "great“ earthquake, they do not mean the earthquake was fabulous, they mean it was huge. Informally, earthquakes are classified according to their magnitude size: under 5 small 5 - 6 moderate 6 - 7 large 7 - 7.8 major 7.8 or above great Intensity Intensity is a qualitative measure of the actual shaking at a location during an earthquake, and is assigned as Roman Capital Numerals . There are many intensity scales. Two commonly used ones are the Modified Marcella Intensity (MMI) Scale and the MSK Scale . Both scales are quite similar and range from I- (least perceptive) to XII-(most severe). The intensity scales are based on three features of shaking. •perception by people and animals, • performance of buildings, and • changes to natural surroundings. Basic Difference: Magnitude versus Intensity Magnitude of an earthquake is a measure of its size. For instance, one can measure the size of an Earthquake by the amount of strain energy released by the fault rupture. This means that the magnitude of the earthquake is a single value for a given earthquake. On the other hand, intensity is an indicator of the severity of shaking generated at a given location. Clearly, the severity of shaking is much higher near the epicenter than farther away. Thus, during the same earthquake of a certain magnitude, different locations experience different levels of intensity.

What is a Seismic Zone? : 

What is a Seismic Zone? A seismic zone is a region in which the rate of seismic activity remains fairly consistent. This may mean that seismic activity is incredibly rare, or that it is extremely common. Some people often use the term “seismic zone” to talk about an area with an increased risk of seismic activity, while others prefer to talk about “seismic hazard zones” when discussing areas where seismic activity is more frequent.

What are the Seismic effects on structures?: 

What are the Seismic effects on structures?

How Building Twist during the Earthquake?: 

How Building Twist during the Earthquake?

What is a Seismograph? : 

What is a Seismograph? Earthquakes generate seismic waves which can be detected with a sensitive instrument called a seismograph . Advances in seismograph technology have increased our understanding of both earthquakes and the Earth itself. Perhaps the earliest seismograph was invented in China A.D. 136 by a m an named Choko.

The First Seismograph : 

The First Seismograph The first seismograph was invented in 132 A.D. by the Chinese astronomer and mathematician Chang Heng. He called it an "earthquake weathercock." Each of the eight dragons had a bronze ball in its mouth. Whenever there was even a slight earth tremor, a mechanism inside the seismograph would open the mouth of one dragon. The bronze ball would fall into the open mouth of one of the toads, making enough noise to alert someone that an earthquake had just happened. Imperial watchman could tell which direction the earthquake came from by seeing which dragon's mouth was empty. In 136 A.D. a Chinese scientist named Choke updated this meter and called it a "seismoscope." Columns of a viscous liquid were used in place of metal balls. The height to which the liquid was washed up the side of the vessel indicated the intensity and a line joining the points of maximum motion also denoted the direction of the tremor.

Earthquake Forecast: 

Earthquake Forecast There are different ways of forecasting an earthquake, for example, by the subterranean waters in wells, by animals’ behavior, etc. We can foresee a disastrous event by analyzing changes of the chemical, gas and isotopic solution of the underground waters. Such sensitive devices like seismographs (Instruments used to detect and record seismic disturbances can be very useful in forecasting. Is it possible that we have some reliable and accurate forecasters of underground processes just at hand? But we are unaware about them and not using their power to help people? They seem to really exist. The inhabitants of the most populated seismically active areas seem are likely to be the first who paid attention to disturbed behavior of many animals right before an earthquake or volcano eruptions. Nowadays, there are 70 species of animals known for reliable earthquake foretellers, which can be called “living seismographs”. Scientifically proved that animals can warn people with their anomalistic behavior about not only continental earthquakes, but also about sea ones of 4-5 points of magnitude in the Richter scale. The closer animals are to the epicenter, the earlier their abnormal behavior starts and the stronger it is.

How the Ground Shakes?: 

How the Ground Shakes? Seismic Waves Large strain energy released during an earthquake travels as seismic waves in all directions through the Earth’s layers, reflecting and refracting at each interface. These waves are of two types - body waves and surface waves ; the latter are restricted to near the Earth’s surface Body waves consist of Primary Waves (P-waves) and Secondary Waves (S-waves) , and surface waves consist of Love waves and Raleigh waves .

PowerPoint Presentation: 

Focal Point: • The point on the fault where slip starts is the Focus or Hypocenter , and the point vertically above this on the surface of the Earth is the Epicenter . The depth of focus from the epicenter, called as Focal Depth , is an important parameter in determining the damaging potential of an earthquake. Most of the damaging earthquakes have shallow focus with focal depths less than about 70km. Distance from epicenter to any point of interest is called epicenter distance .

Consequences of Earthquake : 

Consequences of Earthquake Landslide Tsunami Dirt Volcanoes Disk clouds

Landslide : 

Landslide Landslide is rapid slipping of a mass of earth or rock from a higher elevation to a lower level under the influence of gravity and water lubrication. More specifically, rockslides are the rapid downhill movement of large masses of rock with little or no hydraulic flow, similar to an avalanche.

Tsunami : 

Tsunami Tsunami is a series of catastrophic ocean waves generated by submarine movements, which may be caused by earthquakes, volcanic eruptions, landslides beneath the ocean, or an asteroid striking the earth. Tsunamis are also called seismic sea waves or, popularly, tidal waves. Tsunami, caused by undersea earthquake or an eruption of a underwater volcano, posses great destructive power for the coast. Tsunami spreading speed is from 50 to 1000 km/h, the height of waves in the ocean - from 0,1m to 5m. When tsunamis approach shallow water along a coast, they are slowed, causing their length to shorten and their height to rise sometimes as high as 100 ft (30 m). When they break, they often destroy piers, buildings, and beaches and take human life. One of the best means of prediction is the detection of such earthquakes on the ocean floor with a seismograph network. Tsunamis may be detected by wave gauges, such as those emplaced as part of the Tsunami Warning System operating in the Pacific regions. Measurement of sudden sea level changes from satellites are also used to warn of a potential tsunami

Dirt Volcanoes : 

Dirt Volcanoes Dirt volcanoes appear in low lands boggy areas which consist of mellow rocks like clay, loam or sand. During a strong earthquake they can became liquid and flow to the earth’s surface. In this way, dirt volcanoes in the shape of conical craters are formed. The process takes place not very deep, usually 20-30 meters up to permafrost.

Disk Clouds : 

Disk Clouds This is how disk clouds are formed. During an earthquake, an enormous amount of energy is thrown out. This energy melts the underground ice. The waters evaporate and make dirt clouds.

How to behave during an earthquake?: 

How to behave during an earthquake? The main thing is not to panic. Your behavior depends on a place, where you are.

     If you are at home, you should:: 

If you are at home, you should: take a cover under tough things (a table or a door aperture) stay away from windows, electric devices, or pans on fire put off a source of fire do not go out to balcony, do not use an elevator leave the house, if you can leave your house leaning your back to the wall, especially if you go downstairs

If you are in a car or bus, you should: : 

If you are in a car or bus, you should: do not stop under a bridge, wires, balconies, etc. · go out of the car, if you can

If you are on the street, you should: : 

If you are on the street, you should: · go to a safe place · watch dangerous things

If you are in a public place, you should: : 

If you are in a public place, you should: · try to choose a safe exit · cross your hands on your stomach

Made by: -Yatender Sindhu : 

Made by: - Yatender Sindhu