3. Location Photo Essays

Zone I of least damage risk includes the places of some parts of Punjab and Haryana, essay on earthquake, plain areas of Uttar Pradesh, portions of plains of Bihar and west Bengal, essay on earthquake, delta area of the Godavari, coastal plain areas of Maharashtra and Kerala, desert areas of Rajasthan and most areas of Gujarat except Kutch area. The following are the significant tsunamis in the second essay on earthquake of the 20th century and 21st century: Moderate and intermediate earthquakes are also called as shallow focus and intermediate focus earthquakes respectively. No water could be made available immediately to extinguish the fire because water pipes were also broken and displaced by the earthquake. Start a game now.

Top 5 Essays on Earthquakes Geography Article shared by: An earthquake is a major demonstration of the power of the tectonic forces caused by endogenetic thermal conditions of the interior of the earth. The number indicating magnitude or intensity M on Richter scale ranges between 0 and 9 but in fact the scale has no upper limit of number because it is a logarithmic scale. It is estimated that the total annual energy released by all earthquakes is about ergs, most of this is from a small number of earthquakes of magnitude over 7.

The Bihar earthquake measuring 8. The place of the origin of an earthquake is called focus which is always hidden inside the earth but its depth varies from place to place. The science, that deals with the seismic waves, is called seismology. Volcanic activity is considered to be one of the major causes of earthquakes. In fact, vulcanicity and seismic events are so intimately related to each other that they become cause and effect for each other.

In other words, each volcanic eruption is followed by earthquakes and many of the severe earthquakes cause volcanic eruptions. The explosive violent gases during the process of vulcanicity try to escape upward and hence they push the crustal surface from below with great force and thus is caused severe earth tremor of high magnitude.

It may be pointed out that the magnitude of such earthquakes depends upon the intensity of volcanic eruptions. The violent eruption of Krakatoa volcano between Java and Sumatra caused such a severe earthquake the impact of which was experienced as far away as Cape Horn some 12, km away.

Faulting and Elastic Rebound Theory: In fact, sudden dislocation of rock blocks caused by both tensile and compressive forces triggers immediate earth tremors due to sudden maladjustment of rock blocks. Underground active fault zone was suggested as one of the possible causes of Koyna earthquake Maharashtra of December 11, The stretching and pulling of crustal rocks due to tensile forces is slow process. The rocks continue to be stretched so long as the tensile forces do not exceed the elasticity of the rocks but as the tensile forces exceed the rocks elasticity, they are broken and the broken rock blocks try immediately to occupy their previous positions so that they may adjust themselves.

All these processes occur so rapidly that the equilibrium of the concerned crustal surface is suddenly disturbed and hence earth tremors are caused. The famous earthquake of of California was caused due to creation of a massive fault in the Oven Valley.

Similarly, the Californian earthquake of April 18, , was caused due to the formation of km long San Andreas Fault. The earthquake of Sagami Bay of Japan was also believed to have been triggered by big fault. Krishna Brahman and Janardhan G.

They have claimed to have identified two active rift faults in Maharashtra beneath the Deccan Traps viz. Kurduvadi rift and Koyna rift. According to them Koyna rift begins from Kaladgi in Karnataka and runs for a distance of km through Koyna and terminates 40 km west of Nasik. The km long Kurduvadi rift begins from 40 km south-west of Solapur and after running through Kurduvadi it merges with the Koyna rift to the north of Pune. According to them Bhatsa Dam is located at the junction of Tawi and Koyna faults.

They are of the opinion that gradual increase in the seismic events in Bhatsa Dam area since is because of active faulting beneath the basaltic crust. The Assam earthquake, Bihar earthquake and Bhuj earthquake Gujarat of India were caused mainly by faulting.

Hydrostatic Pressure and Anthropogenic Causes: It may be pointed out that the intensity of earthquake has been positively correlated with the levels of water in the reservoirs. As per theory of the plate tectonics the crust or the earth is composed of solid and moving plates having either continental crust or oceanic crust or even both continental-oceanic crust.

These plates are constantly moving in relation to each Other due to thermal convective currents originating deep within the earth. Thus, all the tectonic events take place along the boundaries of these moving plates.

From the stand point of movement and tectonic events and creation and destruction of geomaterials the plate boundaries are divided into: Major tectonic events associated with these plate boundaries are ruptures and faults along the constructive plate boundaries, faulting and folding along the destructive plate boundaries and transform faults along the conservative plate boundaries.

All sorts of disequilibrium are caused due to different types of plate motions and consequently earthquakes of varying magnitudes are caused. Normally, moderate earthquakes are caused along the constructive plate boundaries because the rate of rupture of the crust and consequent movement of plates away from the mid-oceanic ridges is rather slow and the rate of upwelling of lavas due to fissure flow is also slow.

Consequently, shallow focus earthquakes are caused along the constructive plate boundaries or say along the mid-oceanic ridges. The earthquakes of the Mid-Conti- nental Belt along the Alpine-Himalayan chains are caused due to collision of Eurasian plates and African and Indian plates. The earthquakes of the western marginal areas of North and South Americas are caused because of subduction of Pacific plate beneath the American plate and the resultant tectonic forces whereas the earthquakes of the eastern margins of Asia are originated because of the subduction of Pacific plate under Asiatic plate.

The severe earthquake of Bhuj of Jan. Here one part of California moves north-eastward while the other part moves south-westward along the fault plane and thus is formed transform fault which causes earthquakes. It has become apparent after the discussion of the causes of seismic events that there is wide range of variation in the nature and magnitude of earthquakes. Each earthquake differs from the other and thus it becomes difficult to classify all the earthquakes into certain categories.

Classification on the basis of Causative Factors: A Natural earthquakes are those which are caused by natural processes i. These are further divided into four subcategories: Examples, severe earthquakes caused by violent explosions of Krakatao volcano in and Etna volcano in Such earthquakes are very severe and disastrous.

The centres foci of these earthquakes are generally located within the depths ranging from km to km. Classification on the basis of Focus: Moderate and intermediate earthquakes are also called as shallow focus and intermediate focus earthquakes respectively.

Classification on the basis of Human Casualties: Earthquakes are grouped into 3 categories on the basis of their hazardous impacts in terms of human casualties: Hazardous Effects of Earthquakes: An earthquake becomes hazard and desaster only when it strikes the populated area.

Slope Instability and Failures and Landslides: The shocks produced by earthquakes particularly in those hilly and mountainous areas which are composed of weaker lithologies and are tectonically sensitive and weak cause slope instability and slope failure and ultimately cause landslides and debris falls which damage settlements and transport systems on the lower slope segments.

The shocks generated by Peruvian earthquake of May, triggered off the collapse of ice caps seated on the peak of high mountain called Huascaran of m height near the town of Yungay in Peru. Damage to Human Structures: Thus, the earthquakes cause more damages in the areas of unconsolidated ground than their counterparts in the regions of solid structures and bedrocks. Two major earthquakes of Bihar-Nepal border in and can explain the impact of earthquake disasters on human structures and human lives.

The damage caused by the Bihar earthquake of 15 January, , measuring 8. Damages to the Towns and Cities: Earthquakes have their worst effects on towns and cities because of highest density of buildings and large agglomerations of human populations.

The sad tale of the destruction of Mexico city due to the earthquake of has already been described. Recent Bhuj earthquake of Gujarat Jan. Loss of Human Lives and Property: It may be pointed out that it is not the intensity magnitude of Richter scale of earthquake alone which matters more as regards the human casualities but it is the density of human population and houses which matter more in terms of human deaths and loss of property.

More than 40, people lost their lives in the devastating earthquake of Turkey August 17, which recorded 7. For example, the house wives were cooking their lunches in the kitchens when disastrous killer earthquake struck in the vicinity of Tokyo and Sagami Bay in Consequently, severe fire broke out which claimed the lives of 38, people out of total fatalities of 1,63, caused by the earthquake through various processes.

This earthquake resulted into total loss of property worth 2, million US dollars. The severe earthquake of San Fransisco USA , which occurred on April 18, , caused widespread fires in several parts of the city. No water could be made available immediately to extinguish the fire because water pipes were also broken and displaced by the earthquake.

Two biggest oil refineries of Turkey were completely devastated due to fire caused by the killer earthquake of August 17, 7. Deformation of Ground Surface: The Assam earthquake caused a large fault measuring Several faults were created in the mouth areas of the Mississippi river because of the earthquakes of , and in the Mississippi valley.

The alluvial-filled areas of the flood plains of the Mississippi were fractured at many places which forced ground surface at few places to collapse. This process resulted in the formation of lakes and marshes.

It may be pointed out that subsidence in one area is followed by emergence of the land in other area. This also happened in the Indus delta area as a large area measuring 80 km in length and 26 km in width was raised by 3 m from the surrounding area. Similarly, the coastal land of Chile was raised from 6m to 13 m because of the earthquake of The seafloor of Sagami Bay of Japan was subsided from m to m because of the earthquake of Strong seismic events result in the damages of dams and cause severe flash floods.

Severe floods are also caused because of blocking of water flow of rivers due to rock blocks and debris produced by severe tremors on the hill slopes facing the river valleys.

Sometimes, the blockade of the rivers is so immense that even the main course of the river is changed. Similarly, the dam on Subansiri River broke in and resultant flash flood submerged an area of square kilometres. The Kutch earthquake of June 16, generated strong tsunamis which submerged the coastal areas and inflicted great damage to ships and country-made boats of the fishermen.

The land area measuring 24 km in length was raised upward because of tectonic movement triggered by the said earthquake which provided shelter to the stranded and marooned people. The great tsunamis caused by the Lisbon earthquake of the year in Portugal generated about 12 m high sea waves which damaged most parts of Lisbon city and killed 30, to 60, people.

The impact of this earthquake was so enormous that the waters of inland lakes like Looh Lomond and Looh Ness continued to oscillate for several hours. The strong tsunamis triggered by Lisbon earthquake also caused 3. The earthquake caused by violent volcanic eruption of Karakatoa in caused enormous tsunamis which generated As these waves approach coastal land, the depth of oceanic water decreases but the height of tsunamis increases enormously and when they strike the coast, they cause havoc in the coastal areas.

The best example of tsunami induced by violent volcanic eruption is from Krakatao eruption which occurred in

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