1. UNIT FIVE: SEISMICITYAs per the Syllabus According to our Omnibus Seismic waves Introduction to Earth Earthquakes and faults Tectonic Plates Measures of an earthquake - Faults magnitude & intensity Fundamentals of Earthquakes Ground damage Earthquakes and Tsunamis Tsunamis and earthquakes Ground Damage and Failure Earthquake Resistant Design and Construction The Great Indian Ocean Tsunami, 2004 Gujarat Earthquake, 2001
2. INTRODUCTION TO EARTH
3. SOME FACTS ABOUT THE EARTHEarth is the only planet to be named in English. Theword ‘Earth’ is Old English word for "land“Earth belongs to the Milky Way Galaxy, Local GroupCluster and Virgo Super ClusterEarth is the only planet to sustain lifeEarth is believed to be existent for 450 million years& evidences are from 225 million years
4. SOME FACTS ABOUT THE EARTH
5. SOME FACTS ABOUT THE EARTHEarth is the third planet from the sunEarth is the fifth largest planet in the universeThe distance of the earth from the sun is 149,600,000 kmThe diameter of the sun is 100 times the diameter of the earthThe mass of the earth is 5.972 x 1024 kgThe Surface area of earth is 510,072,000 km²
6. SOME FACTS ABOUT THE EARTHBefore 500 BC, people thought that earth was flat. Butthanks to scientists like Aristotle and Pythagoras, peopleknow that the shape of the earth is spherical. However SirIsaac Newton showed that the earth was not a perfectsphere, but a compressed spheroid.The correct technical term to use will be oblate spheroid, atype of ellipsoid solid formed when an ellipse is rotatedabout its minor axis.The study of size and shape of earth is called geodesy.The diameter of earth at poles is 12715 km (minor axis)The diameter of earth at equator is 12763 km (major axis)
7. STRUCTURE OF EARTHThe structure of earth (alsoreferred as cross–section) isdivided into mainly four layersnamely Crust, Mantle, InnerCore and Outer Core.
8. STRUCTURE OF EARTH Divisions,Thickness & Materials of the layer
9. STRUCTURE OF EARTH CRUSTThe outermost layer of the Earth is the crust. It is also the surface of the earth.This comprises the continents and ocean basins and therefore it has beenclassified into continental crust and oceanic crust.The oceanic crust extends up to a distance of 0-10 kms (5-12 taken asaverage) whereas the continental crust would extend up to 0-75 kms (20-70taken as average).The oceanic crust is mainly composed of basaltic igneous rocks, mainly ofsilica and magnesium and therefore also called SIMA layer.The continental crust is composed of crystalline and granitic rocks mainly ofsilica and aluminum and therefore also called SIAL layer.
10. STRUCTURE OF EARTH MANTLEThe next layer is the mantle, which is composed mainly of iron andmagnesium silicates. It is been referred as FeMa layer.Mantle is also where most of the internal heat of the Earth is located. It isabout 2900 km thick.It can be subdivided into four layers namely(1) Lithosphere (70 – 100 kms)(2) Asthenosphere (100 - 350 kms)(3) Upper Mantle (350 – 670 kms)(4) Lower Mantle (670 – 2900 kms)Mohorovičić discontinuity, usually referred to as the Moho is the transitionboundary between the Earths crust and the mantle.
11. STRUCTURE OF EARTH MANTLEThe lithosphere is the outermost part of the mantle immediately below theMohorovičić discontinuity. It has a part of the tectonic plates that coversurface of Earth.Asthenosphere is a low seismic velocity zone where rocks are at or nearmelting point. It also has a part of tectonic plates.The lower mantle is probably mostly silicon, magnesium and oxygenwith some iron, calcium and aluminum.The upper mantle is made up of mostly olivine and pyroxene(iron/magnesium silicates), calcium and aluminum
12. STRUCTURE OF EARTH OUTER COREThe third layer is outer core. The outer core is a hot and liquid layercomprising mainly of Nickel and (liquid) Iron. Therefore it is referred as NiFeLayer.The outer core may also contain lighter elements such as Si, S, C, or O.The outer core ranges from 2900 kms to 5150 kms and is 2300 km thick.The Earths magnetic field is believed to be controlled by the liquid outercore. It is also believed to be the responsible force of earth’s rotation andelectric currents.The transition space between outer core and mantle is called Gutenbergdiscontinuity
13. STRUCTURE OF EARTH INNER COREThe fourth layer is inner core.This layer stretches from 5150km to 6370 km and is nearly 1200 kmthick.The inner core is mostly made of solid iron and has little amounts ofnickel.It is unattached to the mantle and is suspended in the molten outer core.The inner core is believed to have the extreme temperature and pressureconditions.The transition region between outer core and inner core is called Lehmanndiscontinuity
14. What is tectonic plates? What are the different tectonic plates? What is the history of tectonic plates? Do the tectonic plates move? Briefly explain the movement of plates? What is continental drift? What is the evidence of tectonic plate movement? How do tectonic plates cause earthquakes? What are intraplate and interplate earthquakes?
15. The lithosphere is divided into several slabs orblocks or plates. These plates are supported frombelow by Asthenosphere. These plates are calledLithosphere plates or Tectonic Plates.Some of these plates encompass continents, someof these plates encompass oceans and some of theplates encompass both oceans and continents.
16. The plates are divided into three categoriesPrimary PlatesSecondary PlatesTertiary Plates The primary plates and secondary plates are together called major plates. The tertiary plates are sub divisions of Primary and Secondary Plates
17. PrimaryAfrican PlateAntarctic PlateEurasian PlateIndo-Australian Plate (sometimes Indian and Australian)North American PlatePacific PlateSouth American PlateSecondaryArabian PlateCaribbean PlateCocos PlateJuan de Fuca PlateNazca PlatePhilippine Sea PlateScotia Plate
18. 225 million years ago (Permian) PANGAEA200 million years ago (Triassic)LAURASIA, GONDWANA125 million years ago (Jurassic)NENA,COLUMBIA,ZEALANDIA65 million years ago (Cretaceous)LEMURIACURRENT150 million years laterAMASIA
20. The movement of tectonic plates is believed to be inducedby the asthenosphere which induces heat and convectioncurrents.The plates are capable of drifting with respect to each otheralong their plate boundaries.Based on the plate movement, there are 3 principal type ofboundaries namelyDiverging BoundariesConverging BoundariesTransform Boundaries
22. EXAMPLESDivergent BoundariesNorth American Plate & Eurasian PlateConvergent BoundariesSouth American Plate & Nazca PlateTransform BoundariesNorth American Plate & Pacific Plate near the JDF Plate
23. PLEASE NOTEWhen two continental plates diverge, a rift is created.Eg. East African RiftWhen two oceanic plates diverge, a ridge is created. SeaFloor Spreading is said to occur.Eg. Mid Atlantic RidgeWhen two oceanic plates converge, an island arc andtrench are created.When an oceanic and convergent plate converge, a volcanoand trench are created.When two continental plates converge, a mountain range isformed.
24. PLEASE NOTEWhen two continental plates or oceanic plates orcontinental/oceanic plates transform, EARTHQUAKEHAPPENS If one plate is trying to move past the other, they will be locked until sufficient stress builds up to cause the plates to slip relative to each other. The slipping process creates an earthquake .
25. 6. WHAT IS CONTINENTAL DRIFT?The movement of earth’s continents with respect to eachother due to the movement of tectonic plates is calledcontinental drift.
26. 7. EVIDENCES FOR TECTONIC PLATE MOVEMENTSIMILAR PLANT & ANIMAL FOSSILS IN CONTINENTSSIMILAR LIVING ORGANISMSSIMILAR ROCK TYPES ON CONTINENTSCOMPLEMENTARY ARRANGEMENT OF FACING SIDES OF SOUTHAMERICA & AFRICASEAFLOOR SPREADING DATA
27. 8. INTRAPLATE & INTERPLATE EARTHQUAKES1. An intraplate earthquake is an earthquake that occurs in theinterior of a tectonic plate, whereas an interplate earthquake is onethat occurs at a plate boundary or a plate margin.2. Intraplate earthquakes are very rare whereas interplateearthquakes are quite normal. The recurrence interval of intraplateearthquake is 10 – 30 years while that of interplate earthquakes is100 – 1000 years.3. The effect (magnitude and intensity) of intraplate earthquakes isless when compared with interplate earthquakes.4. Notable examples of damaging intraplate earthquakes are thedevastating Gujarat earthquake in 2001 while that for interplateearthquakes are Chile 1960 Earthquake and
29. THE TWO MOST IMPORTANT REASONS FOREARTHQUAKES 1. TECTONIC PLATES 2. FAULTS
30. FAULTS FAULTS ARE ONE OF THE STRUCTURAL FEATURES OF ROCKS WHILE ROCKS AT OR NEAR THE SURFACE OF THE EARTH ARE COOL & BRITTLE, ROCKS BELOW THE SURFACE OF THE EARTH ARE HOT AND TEND TO MOVE
31. FAULTS A LOT OF EXTERNAL FORCES ACT UPON THE ROCKS AND CAUSE STRESS ON THEM DUE TO THIS STRESSES, ROCKS EITHER UNDERGO DUCTILE DEFORMATION(BEND) OR BRITTLE DEFORMATION(BREAK) IF THEY UNDERGO DUCTILE DEFORMATION, ROCKS DEVELOP FOLDS. IF THEY UNDERGO BRITTLE DEFORMATION, THEY DEVELOP FAULTS.
33. FAULTS FAULT IS DEFINED AS A SPLIT OR CRACK OR FRACRTURE IN THE ROCK PRESENT IN EARTH’S CRUST CHARACTERISED BY RELATIVE DISPLACEMENT OF ONE SIDE OVER THE OTHER. The two sides of a non-vertical fault are known as the hanging wall and footwall. By definition, the hanging wall occurs above the fault plane and the footwall occurs below the fault
35. FAULT LINE A FAULT LINE IS THE INTERSECTION OF A FAULT PLANE AND EARTH SURFACE IT IS THE SURFACE TRACE OF A FAULT
36. FAULT LINE
37. TYPES OF FAULTS FAULTS ARE CLASSIFIED INTO THREE TYPES NAMELY DIP SLIP FAULTS (VERTICAL MOTION) STRIKE SLIP FAULTS (HORIZONTAL MOTION) OBLIQUE SLIP FAULTS (OBLIQUE MOTION)
38. TYPES OF FAULTS
39. DIP SLIP FAULTS A fault where the relative movement on the fault plane is approximately vertical is known as a dip-slip fault.Dip Slip Faults are divided intoNormal Faults (Extension)Reverse Faults/Thrust Faults (Compression)
40. NORMAL FAULTS
41. REVERSE FAULTS
42. DIP SLIP FAULTS When the hanging wall moves down with respect to the footwall, it is called a normal fault. When the hanging wall moves up relative to the footwall, it is called a reverse fault
43. STRIKE SLIP FAULTS A fault where the relative movement on the fault plane is approximately vertical is known as a strike-slip fault. Strike Slip Faults are divided intoLeft Lateral Faults (Sinistral Faults)Right Lateral (Dextral Faults)
44. LEFT LATERAL FAULTS
45. RIGHT LATERAL FAULTS
46. STRIKE SLIP FAULTS If you stand on one side of a fault and the other side slips to the right, then it is called a right- lateral fault. In a left-lateral fault, the movement occurs to your left.
47. SIMPLE DIAGRAMATIC REPRESENTATIONS
48. OBLIQUE SLIP FAULTS A fault where the relative movement on the fault plane is both horizontal and vertical is known as a oblique-slip fault.
49. FAULTS & EARTHQUAKES
50. FAULTS & EARTHQUAKESFAULTS CAN CAUSE TREMENDOUSEARTHQUAKESSTRIKE SLIP FAULTS CAUSE MAJOREARTHQUAKES WHILE OBLIQUE SLIPFAULTS AND DIP SLIP FAULTS CAUSEMINOR EARTHQUAKES.THE OCCURRENCE OF EARTHQUAKESDUE TO FAULTS IS EXPLAINED BY ELASTICREBOUND THEORY.
51. ELASTIC REBOUND THEORY
52. ELASTIC REBOUND THEORY
53. ELASTIC REBOUND THEORY The elastic rebound theory is an explanation for how energy is spread during earthquakes. As plates on opposite sides of a fault are subjected to force and shift, they accumulate energy and slowly deform until their internal strength is exceeded. At that time, a sudden movement occurs along the fault, releasing the accumulated energy, and the rocks snap back to their original undeformed shape.
54. FUNDAMENTALS OF EARTHQUAKES
55. CONTENTS 1. DEFINITION OF AN EARTHQUAKE 2. EARTHQUAKES & SEISMICS 3. CENTRES AND SHOCKS4. INTENSITY AND MAGNITUDE OF EARTHQUAKES 5. CAUSES OF EARTHQUAKE 6. SEISMIC WAVES 7. EFFECT OF EARTHQUAKES 8. WORLD SEISMIC ZONES 9. SEISMIC ZONES OF INDIA
56. Earthquake may simply expressed as a momentaryshock experienced by the earth at a particular locationand time.Earthquake may be technically defined as the vibrationsinduced in the earth’s crust due to internal or externalcauses that give a shock to a part of the crust and allthings existing on it
57. The greek word for earthquake isSeism and therefore the term seismicis associated with earthquakes.The science dealing with the study ofearthquakes is called seismologyThe word seismic is used to qualifyanything related to earthquake suchas seismic intensity, seismic zoning,seismic waves etc.
58. FOCUS OR HYPOCENTREThe point of origin of an earthquake below the surface of earth.EPICENTREThe point on the surface directly above the focus where the vibrationsare felt.
59. SHOCKSA large earthquake is generally preceded and followed bymany smaller shocks.The largest earthquake is called the main shock. Thesmaller ones that occur before the main shock are calledforeshocks and the shocks that occur after the main shockare called aftershocks.
60. INTENSITY MAGNITUDEIntensity is a term used to Magnitude is a term usedmeasure the impact of to establish the size of anearthquake. earthquake.Intensity measures the It is a measure of thestrength of shaking amplitude of a seismicproduced by the wave and is related to theearthquake at a certain amount of energy releasedlocation. during an earthquake.Intensity is determined Magnitude is the totalfrom effects on energy released by anpeople, human earthquake at its focus.structures, and the naturalenvironment. The Richter Scale is most famous to express theMercalli Scale was used magnitude of anto predict intensity. earthquake.
61. INTENSITY AND MAGNITUDEMagnitude and Intensity measure differentcharacteristics of earthquakes. Magnitude is quantitativeand measured using instrument called seismograph.Intensity is qualitative and can be measured usingassessment of the damages.
62. INTENSITY AND MAGNITUDEThe analogy of tube light is used to differentiate betweenmagnitude and intensity.
63. MAGNITUDEMagnitude is the logarithm to base 10 of maximumamplitude traced on the seismogram by an instrumentplaced at 100 km from the epicenter.It can be generally calculated by the formulaM = log (A∆/Ao∆) whereM is Richter magnitude ∆ is epicentral distance A is amplitude of the point to be measured Ao is the maximum amplitude of zero earthquake
64. INTENSITYIntensity is a space dependent descriptive rating ofchanges observed to the ground surface in terms ofdamaging effects. The damaging effects are grounddamage, damage to built environment and to thehumans. These effects are incorporated in a descriptiveintensity scale by a group of experts and denoted byRoman numbers. Maximum intensity is usually close tothe epicenter and it reduces as the epicentral distanceincreases. The lines of same intensity are plotted in acontour map called isoseismal map which is a veryimportant data for earthquake analysis.
65. Nowadays intensity of earthquakes are not measured. They have been replaced by magnitude. Top 5 Earthquakes by Magnitude S. Date Place Magnitude No. 1 22 May 1960 Valdivia, Chile 9.5 2 27 March 1964 Alaska, USA 9.2 3 26 December Sumatra, Indonesia 9.1 2004 4 13 August 1862 Arica,Chile 9.0 5 26 January 1700 Cascadia, USA- 9.0 Canada
66. An earthquake may be caused by the following natural and artificial sources.NATURAL SOURCESTectonic Plates Movement 90%Faults in Rocks (Elastic Rebound Theory) 6%Volcanic Explosions 1%ARTIFICIAL SOURCESExplosion 1%Mine Collapse 1%Reservoir Failure 1%
67. SEISMIC WAVESThe energy released during earthquake travels to the earth in form of waves. The waves are called as P-Waves S-Waves L-Waves (Rayleigh Waves & Love Waves) P-Waves & S-Waves are called as body waves. L- Waves are also called as surface waves.
68. The seismic waves are very useful as follows They were used to establish the internal structure of the earth. They are used to calculate the magnitude of earthquake. Richter Scale is based upon the amplitude of the seismic waves. They are also used to locate the epicenter of earthquakes. They are also used for groundwater and other explorations.
69. Primary, or P waves are the first waves felt during an earthquake and they are the fastest. They move in a compressional, "push-pull" manner similar to a spring They are longitudinal in character. They move only in the direction of prorogation. They temporarily change the volume of the material theyre moving through.They can travel through liquid, solid and gaseous matter.Their velocity increases with depth and decreases after the Gutenberg Discontinuity.
70. Secondary, or S waves, are felt next to P waves.These waves move in an oscillatory/distortional manner similar to shaking a rope.They are transverse in character. They move perpendicular to the direction of prorogation.They temporarily change the shape of the material theyre traveling throughThey can travel through solids only.Their velocity increases with depth and they are absent beyond mantle.
71. L Waves or Long Waves or Surface Waves are finally felt, are felt next to S waves.They are of two types namely – Love Waves and Rayleigh Waves Rayleigh Waves move in a complex manner. They partly move in direction of propagation and partly perpendicular to the direction of prorogation.Love Waves move in the direction of propagation horizontally but in sideways. It is only the Surface Waves cause damage to the building.
72. The effects of earthquakes Loss of Life Building Collapse Ignition of Fire Ground Failure and Rupture Landslides and Avalanches Floods and Tidal Sources TsunamiChange in Soil and Rock Properties
73. WORLD SEISMIC ZONES or EARTHQUAKE HOTSPOTSBased on seismicity, the three most happening earthquake hotspots in the world are1. PACIFIC RING OF FIRE2. ALPIDE BELT3. MID ATLANTIC RIDGE
74. EARTHQUAKES IN INDIAThe major earthquakes in India are2004 Sumatra Earthquake (9.1)1934 Bihar Earthquake (8.7)1950 Assam (Shillong Plateau) Earthquake (8.7)1897 Assam (Tibetian Plateau) Earthquake (8.5)2005 Kashmir Earthquake (7.6)2001 Gujarat(Kutch) Earthquake (7.1)
75. EARTHQUAKES IN INDIA
76. EARTHQUAKE ZONES IN INDIAThere are five seismic zones named as I to V based on Modified MercalliScale (MM Scale) as details given below:Zone V: Covers the areas liable to seismic intensity IX and above on MMScale. This is the most severe seismic zone and is referred here as VeryHigh Damage Risk Zone.Zone IV: Gives the area liable to MM VIII. This, zone is second in severity tozone V. This is referred here as High Damage Risk Zone.Zone III: The associated intensity is MM VII. This is termed here asModerate Damage Risk Zone.Zone II: The probable intensity is MM VI. This zone is referred to as LowDamage Risk Zone.Zone I: Here the maximum intensity is estimated as MM V or less. This zoneis termed here as Very Low Damage Risk Zone.
77. EARTHQUAKE ZONES IN INDIAZone V: Kashmir, Punjab, the western and Central Himalayas, the North-East Indian region and the Rann of Kutch fall in this zone.Zone IV: Indo-Gangetic basin and the capital of the country(Delhi, Jammu)and Bihar fall in Zone 4.Zone III: The Andaman and Nicobar Islands, parts of Kashmir, WesternHimalayas, Western Ghats fall under this zoneZone II: Other parts of India namely Hyderabad, Lakshadweep, Orissa etc.Zone I : No
78. EARTHQUAKE ZONES IN INDIA Cities and Zones• Zone III :- Ahemdabad, Vadodara, Rajkot, Bhavnagar, Surat,Mumbai, Agra, Bhiwandi, Nashik, Kanpur Pune, Bhubneshwar, Cuttack, Asansol, Kochi, Kolkata, Varanasi, Bareilly, Lucknow, Indore, Jabalpur, Vijaywada, Dhanwad, Chennai, Coimbatore, Manglore, Kozhikode ,Trivandrum.• Zone IV :- Dehradun, New Delhi, Jamunanagar, Patna, Meerut, Jammu, Amristar,Jalandhar.• Zone V:- Guwahati and Srinagar.
79. Earthquakesand Tsunamis
80. Overview Meaning of the word Tsunami Definition of Tsunami Characteristics of Tsunami Tsunami Effects Tsunami Vs Tsunami 2004 Formation of Tsunami Tsunami Counter Measures
81. Tsunami- Name MeaningIN JAPANESETSU – HARBOURNAMI – WAVESTSUNAMI means HARBOUR WAVES
82. Tsunami- Definition TSUNAMI IS DEFINED AS SERIES OF GIGANTIC WAVES TRIGGERED IN A LARGE BODY OF WATER BY A DISTURBANCE (LIKE EARTHQUAKE, VOLCANO, LANDSLI DE, METEORITE ETC) THAT DISPLACES WATER VERTICALLY. TSUNAMI HAS SERIOUS EFFECTS IN LOW LYING COASTAL AREAS. IT IS MOSTLY CAUSED BY SUBMARINE EARTHQUAKES
83. Tsunami- Characteristics A TSUNAMI IS CAUSED BY AN EARTHQUAKE WHICH HAS ITS FOCUS LESS THAN 50 km A TSUNAMI IS CAUSED BY AN EARTHQUAKE WHOSE MAGNITUDE IS NORMALLY MORE THAN 9.5 THE WAVELENGTH OF A TSUNAMI CAN BE IN THE ORDER OF 100 – 200 KM THE AMPLITUDE OF TSUNAMI WILL BE BETWEEN 0.3m and 0.6m TSUNAMI CAN OCCUR FOR A PERIOD AS LOW AS 5 MINUTES TO AS LONG AS ONE HOUR THE VELOCTITY OF TSUNAMI IS ABOUT 200 m/s or 720 km/hr.
84. Tsunami- Characteristics THE WAVELENGTH, PERIOD ,AMPLITUDE AND VELOCITY OF A TSUNAMI ARE DEPENDENT ON THE DIMENSIONS OF THE EARTHQUAKE AND THE DEPTH OF WATER. A TSUNAMI OFTEN COMES IN A SERIES OF WAVES , MAY THREE TO FIVE MAJOR OSCILLATIONS SEPERATED BY SMALL INTERVALS OF HALF AN HOUR OR SO. THE TSUNAMI WAVES CAN STRIKE AS HIGH AS 20 – 40 m (60 ft – 140 ft)
85. Tsunami- Characteristics THE TSUNAMI WAVES ARE CHARACTERISED BY APPROACH(COMING IN) AND RETREAT(RECEDING OUT). APPROACH AND RETREAT CAN BE EQUALLY DANGEROUS. THE VELOCITY OF TSUNAMI CAN BE CALCULATED BY FORMULA V2 = (gD) where V = velcity of waves in m/s g = acceleration due to gravity in m/s2 D = depth of water in m
86. Tsunami- Effects EXTENSIVE INUNDATION OF COASTAL AREAS EXTENSIVE RUN UP OF COASTAL AREAS DAMAGE TO COASTAL STRUCTURES LOSS OF BUILT ENVIRONMENT LOSS OF HUMAN LIFE LOSS OF FLORA AND FAUNA CHANGES IN WATER QUALITY AND QUANTITY
87. Tsunami 2004 - Comparison of Stats TSUNAMI TSUNAMI 2004 Earthquake Depth < 50 30 m Earthquake Magnitude > 7.5 9.1 Wavelength 100 – 200 km 180 km Velocity 600 – 800 km/hr 750 km/hr Amplitude 0.3m to 0.6m 0.5m Period 5 min to 1 hour 45 minutes Height of Waves 20m to 40m 35m
88. Tsunami Formation Tsunamis can be generated when the sea floor suddenly displaces the overlying water vertically. When they occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. Waves are formed as the displaced water mass, acting under the force of gravity, tries to regain equilibrium. When large areas of the sea floor elevate or subside, a tsunami can be created.
89. Tsunami Formation As a tsunami leaves the deep ocean and travels toward the shallow coast, it transforms. A tsunami moves at a speed related to the water depth, therefore the tsunami slows as the water depth decreases. The tsunamis energy flux, being dependent on both its wave speed and wave height, remains nearly constant. As a result, the tsunamis speed decreases as it travels into shallower water, and its height increases. When it reaches the coast, it may appear as a rapidly rising or a series of breaking waves.
90. Tsunami Formation As a tsunami reaches the shore, it begins to lose energy . It slows down and height increases when approaching shallow coast Tsunamis reach the coast with tremendous amounts of energy. Destructive power is due to speed and force with which they strike the coastal area. Tsunamis are stronger and retain height longer than waves generated by wind.
91. Tsunami – Counter MeasuresCoastal Protection Structures (Structural) (Sea Walls, Bulk Heads , Revetments , Dikes and Leeves, Breakwaters, Groynes , Jetties and Piers)Coastal Protection Structures (Non Structural) (Vegetation Planting, Groundwater Drainage, Beach Nourishment, Sand Bypassing and Flood Proofing)Tsunami Early Warning Systems (Sensor Networks and Communication Infrastructure) (International and Regional Warning Systems)Coastal Regulations (Avoiding Low Lying Coastal Areas for developmental works)Evacuation Plan
92. GROUND DAMAGEAND FAILURESurface DistortionsLiquefactionFissuresEarthquake FountainSand Boils & Mud FlowsMud VolcanoLandslides & AvalanchesChanges in Surface & Ground Water
93. GROUND DAMAGEDue to an earthquake, as a result ofpassing of seismic waves, the ground orthe surface may be damaged in severalways.Fault can cause earthquakes. In turnearthquakes will also lead to faults. Apartfrom these faults, earthquakes areassociated with eight distinct damages tothe ground
94. GROUND DAMAGESSurface DistortionsLiquefactionFissuresEarthquake FountainSand Boils & Mud FlowsMud VolcanoLandslides & AvalanchesChanges in Surface & Ground Water
95. SURFACE DISTORTIONS (1) After occurrence of some earthquakes, large scale changes in topography take place and the ground surfaces are distorted. (2) This is most dangerous when it occurs along the coastlines. When surface distortions happen at coastlines, there are two possible ways of damage.1. Submergence/Subsidence of Coastline2. Uplift of Coastline
96. SURFACE DISTORTIONS(3) When coastlines subside or submerge, it isaccompanied by transgression of the sea. In casethey uplift, it is accompanied by regression of thesea.(4) Eg. - Due to the Great Indian Ocean Tsunamiof 2004, the Andaman and Nicobar Islandsshowed a large amount of subsidence in thesouthern islands and equal amount of uplift in thenorthern islands. Car Nicobar and Indira Pointsubsided by an amount of 3m leading to waterinundating for 3 km while Austen Bridge wasuplifted by 1.5 m and new shallow coral beachesemerged.
97. LIQUEFACTION(1) Liquefaction is a phenomenon in which thestrength and stiffness of soil is reduced due to theground shaking done by the earthquake.(2) This takes place when there is water table orwater bearing formations (aquifers) at 10m or lessfrom the ground surface(3) Due to liquefaction, the ability of soil to supportthe foundation may decrease and may lead tocollapse of structures built on the soil.
98. LIQUEFACTION(4) Liquefaction of soil tends to cause settlementof ground. It can also lead to sand boils and mudflows.(5) Due to the Great Bihar – Nepal earthquake of1934, a 200 km long and 60 km wide liquefactionbelt was formed and was named as Slump Belt.Within the belt, many buildings tilted and manybuildings settled leading to damage of floors andfoundations.
99. FISSURES(1) After many earthquakes, the grounds show along narrow opening due to the process ofsplitting or separating of land mass. This is calledfissures.(2) The fissures can easily develop in alluvial soilsand can tend to be long, wide and deep in suchsoils.(3) The fissures can disturb the underlying soiland drainage systems. Some fissures havesprouted water and sand like fountains.
100. FISSURES(4) If fissures are found in abundance, then it maylead to other effects like liquefaction, sand boils,mud flows etc.(5) Due to the great Indian Ocean Tsunami of2004, fissures were evident in Andaman TrunkRoad (ATR). The fissures ranged for nearly 200kilometres in this 300 km long road and wasobserved in areas of Baratang, Port Blair andMayabunder.
101. EARTHQUAKE FOUNTAINS(1) When earthquake occurs in areas with plentyof shallow water, the shaking of ground producesfountains, sprouts or geysers. This phenomenonis termed as earthquake fountains.(2) The earthquake fountains may contain water,sand, clay, silt and even debris.(3) The existence of faults in the area ordevelopment of fissures in the area may lead toearthquake fountains.
102. EARTHQUAKE FOUNTAINS(4) Due to the Gujarat Earthquake of 2001,earthquake fountains full of water and soils wereobserved in the areas of Bhachau and Amardi.The fountains rose up to 3m height and emergedmainly from fissures. The fountains were found inadjacent locations in a linear stretch for 4 kms.
103. SAND BOILS & MUD FLOWS(1) Due to an earthquake, when Sand is broughtup into the land and deposited around thesprouted area, it resembles a crater. Thisphenomenon is called sand boils. The sand boilsmay lead to local flooding and silt deposition.When the sand boils are full of mud, they are alsoreferred to as mud flows.(2) Due to the Gujarat Earthquake of 2001, sandboils and mud flows were predominant in theareas adjoining the Rukmavati river.
104. MUD VOLCANO(1) The term mud volcano or mud dome is usedto refer to volcano like formations created byyoung sedimentary soils at plate margins.(2)This phenomenon will take place only atdestructive plate boundaries. The mud volcanoesmay contain hot water mixed with mud and othersurface deposits.(3) The Great Indian Ocean Tsunami 2004caused the eruption of many mud volcanoes inBaratung Island in Andaman Nicobar area. Itejected methane gases and the gas plumecreated fire and explosions.
105. LANDSLIDES & AVALANCHES(1) While landslides and avalanches triggerearthquakes, earthquakes may also inducelandslides and avalanches.(2)The term landslide describe to a wide variety ofprocesses that result in downward movement ofslope forming materials with a distinct zone ofweakness. While landslides are formed from solidrock or soil, Avalanches are formed from snowand ice.(3) Lanslides may either be rotational landslidesor translational landslides, based on themovement of the failure surface.
106. LANDSLIDES & AVALANCHES(4) The Kashmir earthquake of 2005 had sparkeda rotational landslide in Baramulla and Uriregions. The same earthquake had sparked agigantic translational landslide at Sadhna Pass(5) In September 2010, an earthquake atChristchurch, New Zealand triggered more than12 avalanches at the famous Mountain Hutt.
107. CHANGES IN WATER QUALITY(1) The severe ground shaking associated withany earthquake can disturb the ground water andsurface water in a very large area.(2)The changes in water quality can be noticed bychanges in colour, odour, turbidity, hardness,oxygen content etc of surface waters. Thegroundwaters get filled with clay and silt andcannot be used for any purpose.(3) Apart from changing the water quality,earthquakes reduce the quantity of water throughdiversion of surface waters and water levelchanges in groundwater,
108. CHANGES IN WATER QUALITY(4) Due to the Gujarat Earthquake of 2001, thegroundwater wells of Lodai and Tehsil and thesurface waters of Rann of Kutch were heavilyaffected and it took more than 5 years to provideremediation.
109. LAST BUT NOT THE LEASTThe implication of ground damage to builtenvironment is very huge.If buildings and structures are built ondamaged grounds, it poses highvulnerability.In such cases, the structures should beavoided or used only after sufficientground improvement is done.
110. As a part of mitigation measures, it becomesnecessary to reduce our vulnerability to the mostcommon natural disaster – earthquakesExperience in past earthquakes has shown thatmany common buildings and public structureslack basic resistance to earthquake forces.With improved design and construction, it ispossible to provide more resistance toseismic/earthquake forces and thereby preventdamage to structures and thereby to human life.
111. When a new structure is planned, designedand constructed to withstand earthquakes,the process is called earthquake resistantdesign or aseismic design of structures.Seismic Retrofitting is the modification ofexisting structures to make them moreresistant to seismic activity, ground motion,or soil failure due to earthquakes
112. Ten simple steps for earthquake resistant design and constructions are presented in this lecture. Before that here are the basic things to do during an earthquake 1. STAY CALM 2. INSIDE: STAND IN A DOORWAY, OR CROUCH UNDER A DESK OR TABLE, AWAY FROM WINDOWS OR GLASS DIVIDERS 3. OUTSIDE: STAND AWAY FROM BUILDINGS, TREES TELEPHONE AND ELECTRIC LINES 4. ON THE ROAD: DRIVE AWAY FROM UNDERPASSES/OVERPASSES: STOP IN SAFE AREA AND STAY IN A VEHICLE.
113. 1. Symmetry and No Eccentricity While planning and designing a building/structure, great care should be ensured for the symmetry of loads and structures. If there is eccentricity in design (when loads do not coincide with centre of mass), then the earthquake risks are large.2. As per the Code The design and construction of the building should be as per the BIS (Bureau of Indian Standards) codal provision for earthquake resistant design as given under the code book - IS 1893:1984 Criteria for Earthquake Resistant Design of Structures
114. 3. SOLVE THE SOIL The soil on which the proposed building/structure would rest upon should be thoroughly checked for its shear strength, soil liquefaction, presence of water bodies etc. The design for the building should be keeping in with the parameters of the soil4. GET THE BEST MATERIALS For the structure, select quality materials – be it concrete, stones, brick, steel etc. Especially steel having an elongation of above 14% and yield strength of 415N/mm^2 should be used.
115. 1. Symmetry and No Eccentricity While planning and designing a building/structure, great care should be ensured for the symmetry of loads and structures. If there is eccentricity in design (when loads do not coincide with centre of mass), then the earthquake risks are large.2. As per the Code The design and construction of the building should be as per the BIS (Bureau of Indian Standards) codal provision for earthquake resistant design as given under the code book - IS 1893:1984 Criteria for Earthquake Resistant Design of Structures
116. 5. STOREY IS THE STORY While planning and designing a building/structure, do avoid weak storeys. Avoid soft storeys in ground floor, especially at car parks. In a frame, care should be taken to avoid weak column and strong beam design6. ENFORCE REINFORCE The reinforcement design of columns and beams should be done with clear intention to resist lateral forces. A strong reinforcement design would go a long way in ensuring stability against seismic forces
117. 7. JUNCTION AND BRACINGS In the junction of columns and beams, the placement of shear walls symmetrically in both directions of the buildings must be done. Alternatively, the provision of cross bracings would also make the structure stable against earthquakes.8. POST TENSIONING This refers to the provision of unbonded post-tensioning high strength steel tendons to achieve a moment-resisting system that has self- centering capacity against lateral loads like earthquakes.
118. 9. BASE ISOLATION Base isolation is a collection of structural elements of a building that should substantially decouple the buildings structure from the shaking ground thus protecting the buildings integrity and enhancing its seismic performance10. DAMPING During earthquake, certain amount of energy is transferred to the building and the building will dissipate energy either by undergoing large scale movement or sustaining increased internal strains in elements such as the buildings columns and beams. Both of these eventually result in varying degrees of damage. So, by equipping a building with additional devices which have high damping capacity, we can greatly decrease the seismic energy entering the building, and thus decrease building damage
119. GUJARAT EARTHQUAKE 20011. It is called the 2001 Gujarat earthquake or Kutch Earthquake and it occurred on January 26,2001, at 08:46 AM local time and lasted for over two minutes.2. The epicentre was about 9 km south-southwest of the Bhachau Taluka of Kutch District ofGujarat, India.3. The earthquake reached a magnitude of between 7.6 and 7.7 on the Richter magnitude scaleand had a maximum felt intensity of X (Intense) on the Mercalli intensity scale.4. The quake killed around 20,000 people, injured another 165,000 and destroyed nearly 400,000homes. . 21 districts were affected and 600,000 people left homeless. The total property damagewas estimated at 5.5 billion US dollars5. This was an intraplate earthquake, one that occurred at a distance from an active plateboundary, so the area was not well prepared. The 2001 Gujurat earthquake was caused bymovement on a previously unknown south-dipping fault, trending parallel to the inferred riftstructures.
120. THE GREAT INDIAN OCEAN TSUNAMI 2004The 2004 Indian Ocean Tsunami also known as Indonesian tsunami, Sumatra Tsunami orBoxing Day tsunami. was a tsunami triggered by undersea earthquake that occurred at 04:10AM(IST) on Sunday, 26 December 2004.The epicentre of the earthquake was the west coast of Sumatra, Indonesia. The earthquake wascaused by subduction of tectonic plates. With a magnitude of 9.1–9.3, it is the third largestearthquake ever recorded on a seismograph. The earthquake had the longest duration everobserved, between 8.3 and 10 minutesThe Tsunami accounted for a killing of over 230,000 people in fourteen countries, and is one ofthe deadliest natural disasters in recorded history. Indonesia was the hardest-hit country, followedby Sri Lanka, India, and Thailand. The total economic damages were evaluated at more than 20billion US dollarsThe risk of famine and epidemic diseases was extremely high immediately following the tsunamiand it posed the biggest ever disaster management challenge.The entire world came together to offer rehabilitation for the victims affected by the Tsunami.They were involved in rebuilding homes, children protection, setting up communitycentres, providing infrastructure, and establishing means of education and livelihood.