Earthquake-a tragedy to lifeand property• Topic - Earthquake• Academic year - 2012-13• Formative 2nd –Summative1st• Group - 1st
What is Earthquake ?• An earthquake (also known asa tremor or temblor) is theresult of a sudden release ofenergy in the Earths crust thatcreates seismic waves• The effects of earthquakevary upon the magnitude andintensity. Earthquakes occurevery now and then all roundthe world, except in someplaces where earthquakesoccur rarely. The devastationof cities and towns is one ofthe effects of earthquake.• Landslides, Avalanches, Tsunami(Tsu- harbour,Nami-waves), Volcanoes are alsocaused by movement ofearthquakes. Huge rocks cometumbling down the mountainssometimes blocking the pathof rivers. This can cause floods.Houses are broken down byearthquakes.
Causes of EarthquakeEarthquakes are caused by sudden release of energyin rocks. Plates in the form of rocks are moving veryslowly and earthquake occur when moving platesgrind and scrape against each other. The point atwhich an earthquake originates is the focus orhypocenter and the point on the earth’s surface;directly above this is epicenter. The study ofearthquake is called seismology.
Seismometers- The measurment ofearthquakeEarthquakes can be recorded by seismometersup to great distances, because seismic wavestravel through the whole Earths interior. Theabsolute magnitude of a quake isconventionally reported by numbers on theMoment magnitude scale (formerly Richterscale, magnitude 7 causing serious damageover large areas).
What are seismic waves?Every tremor produces different types ofseismic waves, which travel through rock withdifferent velocities:• Longitudinal P-waves (shock- or pressurewaves)• Transverse S-waves (both body waves)• Surface waves — (Rayleigh and Love waves)
Body and Surface waves• Body waves– P or primary waves• fastest waves• travel throughsolids, liquids, or gases• compressionalwave, material movement isin the same direction aswave movement– S or secondary waves• slower than P waves• travel through solids only• shear waves - movematerial perpendicular towave movement• Surface Waves– Travel just below or alongthe ground’s surface– Slower than body waves;rolling and side-to-sidemovement– Especially damaging tobuildings• Body Waves: P and Swaves• Surface Waves: R and Lwaves
• The point of disturbance below the surfaceof the Earth is called, FOCUS
Tectonic plates• There are 7 large and 12 small such plates whichare in continuous distinctive types ofboundaries, that is :convergent boundaries : where plates pusheach other and one plate slides down theother one.divergent boundaries: where plates pullaway from each other.• transformed boundaries :• Earthquake occur due to several causes such asvolcanic eruption, etc. but the plate tectonictheory is the most convincing and widely accepted
Seismological ZoneDepending upon the frequency and intensity of theearthquakes, the whole country can be divided intothree broad seismological zonesHimalayan zoneThe area s most prone to earthquake in India isthe Fold Mountains ranges of the Himalayan zone. Thestates of Jammu and Kashmir, Himachal Pradesh,Uttaranchal, Bihar, the Bihar- Nepal border and northeastern states.The earthquakes in these zones are primarilydue to plate tectonics. The region along the Himalayaswhere two plates meet is highly earthquake prone andhence known as the zone of maximum intensity
The peninsular zoneThe peninsular India has presumablyremained a stable landmass and only fewearthquakes have been experienced in thisregion. This region is, therefore, called thezone of minimum intensity. But the severearthquakes of Konya (1967), Latur (1993) andJabalpur (1997) have raised doubts about theseismic stability of this landmass
Study of Earthquake• The study ofearthquake waves isknown asSEISMOLOGY• The experts whostudy the pattern ofearthquakes areknown asSEISMOLOGISTSThe machine which records theintensity of earthquake is known asSEISMOGRAPH
Hazardous Effects ofEarthquake- Loss of life and property- Damage to infrastructure- Topographical changes- Damage to transport system i.e. roads, railways,highways, airports, marine.- Chances of fire short-circuit.- Chances of Floods – Dams and Embankments candevelop cracks- Chances of outburst of epidemic- Water pipes, sewers are disrupted- Communications such as telephone wires are damaged.- Economic activities like agriculture, industry, trade andtransport are severely affected.
• Date: 26 January 2001• Origin line: 08 hrs.46 min. 42.9 sec. IST• Epicenter: Latitude 23.40° N Longitude 70.28°E• Magnitude: 7.7• Focal Depth: 25 kms.
Bhuj Earthquake 26th January. 2001On the morning of January26, 2001, the Nation’s 52nd RepublicDay, a devastating earthquakeoccurred in the and Chennai in thesouth. Kutch district of the stateof Gujarat.The earthquake was felt as far awayas Delhi in the north, Kolkata in theeast Bhuj town and the villageBhachau, 60 km east of Bhuj, were
There were more than 20,000deaths and 167 Around 300,000families and at least 3 millionchildren aged 14 and under wereaffected. Around 600,000people were left homeless. Inthe city of Bhuj, more than3,000 inhabitants of the citylost their lives; the mainhospital was crushed and close
Earthquake safety rulesIf you are in a house• don’t use lift for getting down from building• be prepared to move with your familyIf you are in shop, school, office or theater• Don’t run for an exit. Stampede could prove fatal• take cover under a desk/table• move to corner or side walls• move away from window glass• Do not go near electric points and cable. Keep awayfrom weak portion of the building and false ceiling
If you are in high rise building- take protection under a desk/table- don’t rush for exits- stay in the building until the shaking stops- don’t use elevatorIf you are outside- avoid high buildings, walls, power lines andother objects that could fall and create block- don’t run through streets- If possible, move on to an open area awayfrom hazard including trees.If you are in vehicle- stop in a safe and open place- remain inside vehicle- close windows, doors and vents
After an Earthquake• Keep calm, switch on the transistor radio and obeyinstructions• Keep away from beaches and low banks of river. Ahuge wave may sweep in• Expect aftershocks• Turn off the water, gas and electricity• Do not smoke, light match or use a cigarette lighter• Do not turn on switches there may be gas leak orshort circuit• If there is any fire, try to put it out or call firebrigade
Earthquake proof buildingAn earthquake-proof building isa building that has been built tosurvive an earthquake. Thebuilding is built with specialtechnology that has materialsmade in earthquake areas. Nobuilding, however, can be made100% safe.
Can Earthquakes be Predicted?Earthquake Prediction Programs– include laboratory and field studies of rocks before, during,and after earthquakes– monitor activity along major faults– produce risk assessments
Can Earthquakes be Predicted?Earthquake Precursors– changes in elevation or tilting of land surface, fluctuations ingroundwater levels, magnetic field, electrical resistance of the ground– seismic dilatancy model– seismic gaps